AI Trajectory

null

{
  "EnableConfigs": [
    "MHI_BUS",
    "MHI_BUS_PCI_GENERIC",
    "WWAN",
    "MHI_WWAN_CTRL"
  ],
  "FocusSymbols": [
    "mhi_wwan_dtr_probe",
    "mhi_wwan_dtr_remove",
    "mhi_wwan_dtr_ul_xfer_cb",
    "mhi_wwan_dtr_dl_xfer_cb",
    "mhi_wwan_ctrl_dtr_rts",
    "wwan_remove_port",
    "wwan_port_fops_at_ioctl",
    "wwan_port_op_start",
    "wwan_port_op_stop"
  ],
  "KMSANReasoning": "The patch introduces a new feature to signal DTR/RTS lines over the IP_CTRL channel in the MHI WWAN CTRL driver. It allocates a new message structure `struct mhi_dtr_ctrl_msg` using `kzalloc_obj`, which guarantees that the allocated memory is fully zero-initialized. The structure is also marked as `__packed`, eliminating any potential padding bytes. The message is then populated with data and sent to the device via `mhi_queue_buf`. Since the memory is fully initialized before being sent, there is no risk of exposing uninitialized memory to the device or userspace. The receive buffer `rx_buf` is used as a sink for `DMA_FROM_DEVICE` and is also part of a zero-initialized structure (`dtr` allocated via `kzalloc_obj`). It does not send uninitialized memory. Any potential memory safety issues, such as out-of-bounds accesses or use-after-free bugs, would be caught by standard KASAN and other bug detectors. Therefore, a dedicated KMSAN fuzzing session is not required.",
  "NeedsKMSAN": false,
  "Reasoning": "The patch adds DTR/RTS signaling support to the WWAN core and implements it for the MHI WWAN control driver. It introduces a new MHI driver `mhi_wwan_dtr_driver` that binds to the \"IP_CTRL\" channel to send and receive DTR/RTS messages. The MHI bus and its PCI controller driver (`mhi_pci_generic`) can be fuzzed using syzkaller's PCI fuzzer, which can emulate the MHI controller's registers and event rings to trigger device creation. The WWAN core changes are reachable via the WWAN character devices.",
  "WorthFuzzing": true
}

null

{
  "PatchDiff": "commit bccfd7fceb0f5ff3027b8976586907c5038dbdec\nAuthor: syz-cluster \u003ctriage@syzkaller.com\u003e\nDate:   Wed Aug 19 23:21:27 2026 +0000\n\n    syz-cluster: applied patch under review\n\ndiff --git a/drivers/bus/mhi/host/pci_generic.c b/drivers/bus/mhi/host/pci_generic.c\nindex 0d0d9c7ffa4bf..ba47dd153837e 100644\n--- a/drivers/bus/mhi/host/pci_generic.c\n+++ b/drivers/bus/mhi/host/pci_generic.c\n@@ -728,6 +728,8 @@ static const struct mhi_channel_config mhi_sierra_em919x_channels[] = {\n \tMHI_CHANNEL_CONFIG_DL(13, \"MBIM\", 128, 0),\n \tMHI_CHANNEL_CONFIG_UL(14, \"QMI\", 32, 0),\n \tMHI_CHANNEL_CONFIG_DL(15, \"QMI\", 32, 0),\n+\tMHI_CHANNEL_CONFIG_UL(18, \"IP_CTRL\", 32, 0),\n+\tMHI_CHANNEL_CONFIG_DL(19, \"IP_CTRL\", 32, 0),\n \tMHI_CHANNEL_CONFIG_UL(32, \"DUN\", 32, 0),\n \tMHI_CHANNEL_CONFIG_DL(33, \"DUN\", 32, 0),\n \tMHI_CHANNEL_CONFIG_HW_UL(100, \"IP_HW0\", 512, 1),\ndiff --git a/drivers/net/wwan/mhi_wwan_ctrl.c b/drivers/net/wwan/mhi_wwan_ctrl.c\nindex a31d8540fbb85..1cb91b59256e9 100644\n--- a/drivers/net/wwan/mhi_wwan_ctrl.c\n+++ b/drivers/net/wwan/mhi_wwan_ctrl.c\n@@ -1,8 +1,12 @@\n // SPDX-License-Identifier: GPL-2.0-only\n /* Copyright (c) 2021, Linaro Ltd \u003cloic.poulain@linaro.org\u003e */\n #include \u003clinux/kernel.h\u003e\n+#include \u003clinux/list.h\u003e\n #include \u003clinux/mhi.h\u003e\n #include \u003clinux/module.h\u003e\n+#include \u003clinux/mutex.h\u003e\n+#include \u003clinux/slab.h\u003e\n+#include \u003clinux/termios.h\u003e\n #include \u003clinux/wwan.h\u003e\n \n /* MHI wwan flags */\n@@ -14,6 +18,31 @@ enum mhi_wwan_flags {\n \n #define MHI_WWAN_MAX_MTU\t0x8000\n \n+/* IP_CTRL channel message that sets the modem's DTR/RTS control lines */\n+struct mhi_dtr_ctrl_msg {\n+\t__le32 preamble;\n+\t__le32 msg_id;\n+\t__le32 dest_id;\n+\t__le32 size;\n+\t__le32 msg;\n+} __packed;\n+\n+#define MHI_DTR_CTRL_MAGIC\t0x4C525443\t/* 'CTRL' */\n+#define MHI_DTR_MSG_DTR\t\tBIT(0)\n+#define MHI_DTR_MSG_RTS\t\tBIT(1)\n+#define MHI_DTR_HOST_STATE\t0x10\n+\n+/* Per-controller IP_CTRL channel, used to signal DTR/RTS to that modem */\n+struct mhi_wwan_dtr {\n+\tstruct mhi_controller *cntrl;\n+\tstruct mhi_device *mhi_dev;\n+\tstruct list_head node;\n+\tu8 rx_buf[sizeof(struct mhi_dtr_ctrl_msg)]; /* sink for modem serial-state DL */\n+};\n+\n+static LIST_HEAD(mhi_wwan_dtr_list);\n+static DEFINE_MUTEX(mhi_wwan_dtr_lock);\n+\n struct mhi_wwan_dev {\n \t/* Lower level is a mhi dev, upper level is a wwan port */\n \tstruct mhi_device *mhi_dev;\n@@ -103,6 +132,61 @@ static void mhi_wwan_ctrl_refill_work(struct work_struct *work)\n \t}\n }\n \n+/* Signal the modem's DTR/RTS lines over its own controller's IP_CTRL channel */\n+static int mhi_wwan_ctrl_send_dtr(struct mhi_wwan_dev *mhiwwan, unsigned int mdmbits)\n+{\n+\tstruct mhi_controller *cntrl = mhiwwan-\u003emhi_dev-\u003emhi_cntrl;\n+\tstruct mhi_device *ctrl_dev = NULL;\n+\tstruct mhi_dtr_ctrl_msg *dtr_msg;\n+\tstruct mhi_wwan_dtr *dtr;\n+\tu32 msg = 0;\n+\tint ret;\n+\n+\tguard(mutex)(\u0026mhi_wwan_dtr_lock);\n+\n+\tlist_for_each_entry(dtr, \u0026mhi_wwan_dtr_list, node) {\n+\t\tif (dtr-\u003ecntrl == cntrl) {\n+\t\t\tctrl_dev = dtr-\u003emhi_dev;\n+\t\t\tbreak;\n+\t\t}\n+\t}\n+\tif (!ctrl_dev) {\n+\t\tdev_dbg(\u0026mhiwwan-\u003emhi_dev-\u003edev,\n+\t\t\t\"IP_CTRL not enumerated; DTR/RTS not signalled to modem\\n\");\n+\t\treturn 0;\n+\t}\n+\n+\tdtr_msg = kzalloc_obj(*dtr_msg);\n+\tif (!dtr_msg)\n+\t\treturn -ENOMEM;\n+\n+\tif (mdmbits \u0026 TIOCM_DTR)\n+\t\tmsg |= MHI_DTR_MSG_DTR;\n+\tif (mdmbits \u0026 TIOCM_RTS)\n+\t\tmsg |= MHI_DTR_MSG_RTS;\n+\n+\tdtr_msg-\u003epreamble = cpu_to_le32(MHI_DTR_CTRL_MAGIC);\n+\tdtr_msg-\u003emsg_id = cpu_to_le32(MHI_DTR_HOST_STATE);\n+\tdtr_msg-\u003edest_id = cpu_to_le32(mhiwwan-\u003emhi_dev-\u003eul_chan_id);\n+\tdtr_msg-\u003esize = cpu_to_le32(sizeof(__le32));\n+\tdtr_msg-\u003emsg = cpu_to_le32(msg);\n+\n+\tret = mhi_queue_buf(ctrl_dev, DMA_TO_DEVICE, dtr_msg, sizeof(*dtr_msg),\n+\t\t\t    MHI_EOT);\n+\tif (ret) {\n+\t\tdev_dbg(\u0026mhiwwan-\u003emhi_dev-\u003edev,\n+\t\t\t\"failed to queue DTR/RTS signal: %d\\n\", ret);\n+\t\tkfree(dtr_msg);\n+\t}\n+\n+\treturn ret;\n+}\n+\n+static void mhi_wwan_ctrl_dtr_rts(struct wwan_port *port, unsigned int mdmbits)\n+{\n+\tmhi_wwan_ctrl_send_dtr(wwan_port_get_drvdata(port), mdmbits);\n+}\n+\n static int mhi_wwan_ctrl_start(struct wwan_port *port)\n {\n \tstruct mhi_wwan_dev *mhiwwan = wwan_port_get_drvdata(port);\n@@ -163,6 +247,7 @@ static const struct wwan_port_ops wwan_pops = {\n \t.start = mhi_wwan_ctrl_start,\n \t.stop = mhi_wwan_ctrl_stop,\n \t.tx = mhi_wwan_ctrl_tx,\n+\t.dtr_rts = mhi_wwan_ctrl_dtr_rts,\n };\n \n static void mhi_ul_xfer_cb(struct mhi_device *mhi_dev,\n@@ -255,6 +340,71 @@ static void mhi_wwan_ctrl_remove(struct mhi_device *mhi_dev)\n \tkfree(mhiwwan);\n }\n \n+/* IP_CTRL channel driver, bound separately so the data-port path is untouched */\n+static void mhi_wwan_dtr_ul_xfer_cb(struct mhi_device *mhi_dev,\n+\t\t\t\t    struct mhi_result *mhi_result)\n+{\n+\t/* MHI core has done with the buffer, release it */\n+\tkfree(mhi_result-\u003ebuf_addr);\n+}\n+\n+static void mhi_wwan_dtr_dl_xfer_cb(struct mhi_device *mhi_dev,\n+\t\t\t\t    struct mhi_result *mhi_result)\n+{\n+\tstruct mhi_wwan_dtr *dtr = dev_get_drvdata(\u0026mhi_dev-\u003edev);\n+\n+\t/* Modem serial state not needed; requeue the sink buffer to keep DL ring live */\n+\tmhi_queue_buf(mhi_dev, DMA_FROM_DEVICE, dtr-\u003erx_buf,\n+\t\t      sizeof(dtr-\u003erx_buf), MHI_EOT);\n+}\n+\n+static int mhi_wwan_dtr_probe(struct mhi_device *mhi_dev,\n+\t\t\t      const struct mhi_device_id *id)\n+{\n+\tstruct mhi_wwan_dtr *dtr;\n+\tint ret;\n+\n+\tdtr = kzalloc_obj(*dtr);\n+\tif (!dtr)\n+\t\treturn -ENOMEM;\n+\n+\tret = mhi_prepare_for_transfer(mhi_dev);\n+\tif (ret) {\n+\t\tkfree(dtr);\n+\t\treturn ret;\n+\t}\n+\n+\tdtr-\u003ecntrl = mhi_dev-\u003emhi_cntrl;\n+\tdtr-\u003emhi_dev = mhi_dev;\n+\tdev_set_drvdata(\u0026mhi_dev-\u003edev, dtr);\n+\n+\tret = mhi_queue_buf(mhi_dev, DMA_FROM_DEVICE, dtr-\u003erx_buf,\n+\t\t\t    sizeof(dtr-\u003erx_buf), MHI_EOT);\n+\tif (ret) {\n+\t\tmhi_unprepare_from_transfer(mhi_dev);\n+\t\tkfree(dtr);\n+\t\treturn ret;\n+\t}\n+\n+\tmutex_lock(\u0026mhi_wwan_dtr_lock);\n+\tlist_add(\u0026dtr-\u003enode, \u0026mhi_wwan_dtr_list);\n+\tmutex_unlock(\u0026mhi_wwan_dtr_lock);\n+\n+\treturn 0;\n+}\n+\n+static void mhi_wwan_dtr_remove(struct mhi_device *mhi_dev)\n+{\n+\tstruct mhi_wwan_dtr *dtr = dev_get_drvdata(\u0026mhi_dev-\u003edev);\n+\n+\tmutex_lock(\u0026mhi_wwan_dtr_lock);\n+\tlist_del(\u0026dtr-\u003enode);\n+\tmutex_unlock(\u0026mhi_wwan_dtr_lock);\n+\n+\tmhi_unprepare_from_transfer(mhi_dev);\n+\tkfree(dtr);\n+}\n+\n static const struct mhi_device_id mhi_wwan_ctrl_match_table[] = {\n \t{ .chan = \"DUN\", .driver_data = WWAN_PORT_AT },\n \t{ .chan = \"DUN2\", .driver_data = WWAN_PORT_AT },\n@@ -278,7 +428,45 @@ static struct mhi_driver mhi_wwan_ctrl_driver = {\n \t},\n };\n \n-module_mhi_driver(mhi_wwan_ctrl_driver);\n+static const struct mhi_device_id mhi_wwan_dtr_match_table[] = {\n+\t{ .chan = \"IP_CTRL\" },\n+\t{},\n+};\n+MODULE_DEVICE_TABLE(mhi, mhi_wwan_dtr_match_table);\n+\n+static struct mhi_driver mhi_wwan_dtr_driver = {\n+\t.id_table = mhi_wwan_dtr_match_table,\n+\t.remove = mhi_wwan_dtr_remove,\n+\t.probe = mhi_wwan_dtr_probe,\n+\t.ul_xfer_cb = mhi_wwan_dtr_ul_xfer_cb,\n+\t.dl_xfer_cb = mhi_wwan_dtr_dl_xfer_cb,\n+\t.driver = {\n+\t\t.name = \"mhi_wwan_dtr\",\n+\t},\n+};\n+\n+static int __init mhi_wwan_ctrl_init(void)\n+{\n+\tint ret;\n+\n+\tret = mhi_driver_register(\u0026mhi_wwan_dtr_driver);\n+\tif (ret)\n+\t\treturn ret;\n+\n+\tret = mhi_driver_register(\u0026mhi_wwan_ctrl_driver);\n+\tif (ret)\n+\t\tmhi_driver_unregister(\u0026mhi_wwan_dtr_driver);\n+\n+\treturn ret;\n+}\n+module_init(mhi_wwan_ctrl_init);\n+\n+static void __exit mhi_wwan_ctrl_exit(void)\n+{\n+\tmhi_driver_unregister(\u0026mhi_wwan_ctrl_driver);\n+\tmhi_driver_unregister(\u0026mhi_wwan_dtr_driver);\n+}\n+module_exit(mhi_wwan_ctrl_exit);\n \n MODULE_LICENSE(\"GPL v2\");\n MODULE_DESCRIPTION(\"MHI WWAN CTRL Driver\");\ndiff --git a/drivers/net/wwan/wwan_core.c b/drivers/net/wwan/wwan_core.c\nindex ffbcf11e4e681..3a6a0c5a3acf4 100644\n--- a/drivers/net/wwan/wwan_core.c\n+++ b/drivers/net/wwan/wwan_core.c\n@@ -685,6 +685,12 @@ void wwan_remove_port(struct wwan_port *port)\n \n \tmutex_lock(\u0026port-\u003eops_lock);\n \tif (port-\u003estart_count) {\n+\t\tif (port-\u003etype == WWAN_PORT_AT \u0026\u0026 port-\u003eops-\u003edtr_rts) {\n+\t\t\tmutex_lock(\u0026port-\u003edata_lock);\n+\t\t\tport-\u003eat_data.mdmbits \u0026= ~(TIOCM_DTR | TIOCM_RTS);\n+\t\t\tmutex_unlock(\u0026port-\u003edata_lock);\n+\t\t\tport-\u003eops-\u003edtr_rts(port, 0);\n+\t\t}\n \t\tport-\u003eops-\u003estop(port);\n \t\tport-\u003estart_count = 0;\n \t}\n@@ -759,8 +765,17 @@ static int wwan_port_op_start(struct wwan_port *port)\n \tif (!port-\u003estart_count)\n \t\tret = port-\u003eops-\u003estart(port);\n \n-\tif (!ret)\n+\tif (!ret) {\n \t\tport-\u003estart_count++;\n+\t\t/* Mirror TTY semantics: raise DTR/RTS on first open of an AT port */\n+\t\tif (port-\u003estart_count == 1 \u0026\u0026 port-\u003etype == WWAN_PORT_AT \u0026\u0026\n+\t\t    port-\u003eops-\u003edtr_rts) {\n+\t\t\tmutex_lock(\u0026port-\u003edata_lock);\n+\t\t\tport-\u003eat_data.mdmbits |= TIOCM_DTR | TIOCM_RTS;\n+\t\t\tmutex_unlock(\u0026port-\u003edata_lock);\n+\t\t\tport-\u003eops-\u003edtr_rts(port, port-\u003eat_data.mdmbits);\n+\t\t}\n+\t}\n \n out_unlock:\n \tmutex_unlock(\u0026port-\u003eops_lock);\n@@ -773,6 +788,13 @@ static void wwan_port_op_stop(struct wwan_port *port)\n \tmutex_lock(\u0026port-\u003eops_lock);\n \tport-\u003estart_count--;\n \tif (!port-\u003estart_count) {\n+\t\t/* Mirror TTY semantics: drop DTR/RTS on last close of an AT port */\n+\t\tif (port-\u003eops \u0026\u0026 port-\u003etype == WWAN_PORT_AT \u0026\u0026 port-\u003eops-\u003edtr_rts) {\n+\t\t\tmutex_lock(\u0026port-\u003edata_lock);\n+\t\t\tport-\u003eat_data.mdmbits \u0026= ~(TIOCM_DTR | TIOCM_RTS);\n+\t\t\tmutex_unlock(\u0026port-\u003edata_lock);\n+\t\t\tport-\u003eops-\u003edtr_rts(port, port-\u003eat_data.mdmbits);\n+\t\t}\n \t\tif (port-\u003eops)\n \t\t\tport-\u003eops-\u003estop(port);\n \t\tskb_queue_purge(\u0026port-\u003erxq);\n@@ -980,6 +1002,7 @@ static long wwan_port_fops_at_ioctl(struct wwan_port *port, unsigned int cmd,\n \t\t\t\t    unsigned long arg)\n {\n \tint ret = 0;\n+\tbool call_dtr_rts = false;\n \n \tmutex_lock(\u0026port-\u003edata_lock);\n \n@@ -1036,6 +1059,8 @@ static long wwan_port_fops_at_ioctl(struct wwan_port *port, unsigned int cmd,\n \t\t\tport-\u003eat_data.mdmbits |= mdmbits;\n \t\telse\n \t\t\tport-\u003eat_data.mdmbits = mdmbits;\n+\t\tif (port-\u003etype == WWAN_PORT_AT)\n+\t\t\tcall_dtr_rts = true;\n \t\tbreak;\n \t}\n \n@@ -1061,6 +1086,19 @@ static long wwan_port_fops_at_ioctl(struct wwan_port *port, unsigned int cmd,\n \n \tmutex_unlock(\u0026port-\u003edata_lock);\n \n+\tif (call_dtr_rts) {\n+\t\tunsigned int bits;\n+\n+\t\tmutex_lock(\u0026port-\u003eops_lock);\n+\t\tif (port-\u003eops \u0026\u0026 port-\u003eops-\u003edtr_rts) {\n+\t\t\tmutex_lock(\u0026port-\u003edata_lock);\n+\t\t\tbits = port-\u003eat_data.mdmbits;\n+\t\t\tmutex_unlock(\u0026port-\u003edata_lock);\n+\t\t\tport-\u003eops-\u003edtr_rts(port, bits);\n+\t\t}\n+\t\tmutex_unlock(\u0026port-\u003eops_lock);\n+\t}\n+\n \treturn ret;\n }\n \ndiff --git a/include/linux/wwan.h b/include/linux/wwan.h\nindex 1e0e2cb535799..57406139304ea 100644\n--- a/include/linux/wwan.h\n+++ b/include/linux/wwan.h\n@@ -57,6 +57,8 @@ struct wwan_port;\n  * @tx_blocking: Optional blocking routine that sends WWAN port protocol data\n  *               to the device.\n  * @tx_poll: Optional routine that sets additional TX poll flags.\n+ * @dtr_rts: Optional routine that updates the modem control lines to match\n+ *           @mdmbits (a TIOCM_* bitmask). Only called for WWAN_PORT_AT ports.\n  *\n  * The wwan_port_ops structure contains a list of low-level operations\n  * that control a WWAN port device. All functions are mandatory unless specified.\n@@ -70,6 +72,7 @@ struct wwan_port_ops {\n \tint (*tx_blocking)(struct wwan_port *port, struct sk_buff *skb);\n \t__poll_t (*tx_poll)(struct wwan_port *port, struct file *filp,\n \t\t\t    poll_table *wait);\n+\tvoid (*dtr_rts)(struct wwan_port *port, unsigned int mdmbits);\n };\n \n /** struct wwan_port_caps - The WWAN port capbilities\n"
}

best-expensive

null

{
  "EnableConfigs": [
    "MHI_BUS",
    "MHI_BUS_PCI_GENERIC",
    "WWAN",
    "MHI_WWAN_CTRL"
  ],
  "FocusSymbols": [
    "mhi_wwan_dtr_probe",
    "mhi_wwan_dtr_remove",
    "mhi_wwan_dtr_ul_xfer_cb",
    "mhi_wwan_dtr_dl_xfer_cb",
    "mhi_wwan_ctrl_dtr_rts",
    "wwan_remove_port",
    "wwan_port_fops_at_ioctl",
    "wwan_port_op_start",
    "wwan_port_op_stop"
  ],
  "Reasoning": "The patch adds DTR/RTS signaling support to the WWAN core and implements it for the MHI WWAN control driver. It introduces a new MHI driver `mhi_wwan_dtr_driver` that binds to the \"IP_CTRL\" channel to send and receive DTR/RTS messages. The MHI bus and its PCI controller driver (`mhi_pci_generic`) can be fuzzed using syzkaller's PCI fuzzer, which can emulate the MHI controller's registers and event rings to trigger device creation. The WWAN core changes are reachable via the WWAN character devices.",
  "WorthFuzzing": true
}

You are an expert Linux kernel maintainer.
Your job is to review a provided patch series and determine
if it makes functional changes to the kernel that should be fuzzed.

IMPORTANT: The changes have ALREADY been applied and committed as the HEAD commit in
your workspace. Do NOT rely on your internal knowledge of the kernel. You must actively
use your code access tools to examine the actual source code and confirm any assumptions.

Return WorthFuzzing=false if the patch only contains:
- Modifications to Documentation/, Kconfig files, or code comments.
- Purely decorative changes, such as logging (e.g., pr_err, printk) or tracepoints.
- Changes to numeric constants or macros that do not functionally alter execution flow.
- Code paths that are impossible to reach in virtualized environments like GCE or QEMU,
  even when utilizing software-emulated hardware (e.g., usb gadget, mac80211_hwsim).
- Code in vendor-specific PCIe switch, SmartNIC, or GPU drivers (e.g., mlxsw, pds_core, qed,
  ionic, amdgpu) that require physical PCIe hardware cards not emulated in standard QEMU.
- Driver .remove, .shutdown, or pci_unregister_driver teardown callbacks (e.g., igb_remove)
  that are executed only during PCI hot-unplug or sysfs driver unbind operations.

If it modifies reachable core kernel logic, drivers, or architectures, use your code search
tools to verify the code can be executed, then return WorthFuzzing=true.

When returning WorthFuzzing=true, you MUST ALSO:
1. Extract any specific kernel functions that should be heavily fuzzed into FocusSymbols.
   Avoid listing generic hot-path functions to prevent skewed test distributions.
   Prefer non-static, non-inlined API entrypoint functions over internal static helper functions
   (which are inlined by the compiler and do not have distinct symbol addresses).
2. Identify any specific CONFIG_ options required to properly test this new/modified feature.
   Go and look into the Kconfig files and check for ifdefs around the code, do not make assumptions.
   Also check "depends on" lines in Kconfig to include any non-standard parent subsystem configs
   needed for Kbuild to compile the code statically into vmlinux. List them in the EnableConfigs
   output array, and DO NOT add a 'CONFIG_' prefix (e.g., return "NET_IPV4" instead of "CONFIG_NET_IPV4").
Prefer calling several tools at the same time to save round-trips.


Use set-results tool to provide results of the analysis.
It must be called exactly once before the final reply.
Ignore results of this tool.

For your convenience, here is the diff of the changes:
commit bccfd7fceb0f5ff3027b8976586907c5038dbdec
Author: syz-cluster <triage@syzkaller.com>
Date:   Wed Aug 19 23:21:27 2026 +0000

    syz-cluster: applied patch under review

diff --git a/drivers/bus/mhi/host/pci_generic.c b/drivers/bus/mhi/host/pci_generic.c
index 0d0d9c7ffa4bf..ba47dd153837e 100644
--- a/drivers/bus/mhi/host/pci_generic.c
+++ b/drivers/bus/mhi/host/pci_generic.c
@@ -728,6 +728,8 @@ static const struct mhi_channel_config mhi_sierra_em919x_channels[] = {
 	MHI_CHANNEL_CONFIG_DL(13, "MBIM", 128, 0),
 	MHI_CHANNEL_CONFIG_UL(14, "QMI", 32, 0),
 	MHI_CHANNEL_CONFIG_DL(15, "QMI", 32, 0),
+	MHI_CHANNEL_CONFIG_UL(18, "IP_CTRL", 32, 0),
+	MHI_CHANNEL_CONFIG_DL(19, "IP_CTRL", 32, 0),
 	MHI_CHANNEL_CONFIG_UL(32, "DUN", 32, 0),
 	MHI_CHANNEL_CONFIG_DL(33, "DUN", 32, 0),
 	MHI_CHANNEL_CONFIG_HW_UL(100, "IP_HW0", 512, 1),
diff --git a/drivers/net/wwan/mhi_wwan_ctrl.c b/drivers/net/wwan/mhi_wwan_ctrl.c
index a31d8540fbb85..1cb91b59256e9 100644
--- a/drivers/net/wwan/mhi_wwan_ctrl.c
+++ b/drivers/net/wwan/mhi_wwan_ctrl.c
@@ -1,8 +1,12 @@
 // SPDX-License-Identifier: GPL-2.0-only
 /* Copyright (c) 2021, Linaro Ltd <loic.poulain@linaro.org> */
 #include <linux/kernel.h>
+#include <linux/list.h>
 #include <linux/mhi.h>
 #include <linux/module.h>
+#include <linux/mutex.h>
+#include <linux/slab.h>
+#include <linux/termios.h>
 #include <linux/wwan.h>
 
 /* MHI wwan flags */
@@ -14,6 +18,31 @@ enum mhi_wwan_flags {
 
 #define MHI_WWAN_MAX_MTU	0x8000
 
+/* IP_CTRL channel message that sets the modem's DTR/RTS control lines */
+struct mhi_dtr_ctrl_msg {
+	__le32 preamble;
+	__le32 msg_id;
+	__le32 dest_id;
+	__le32 size;
+	__le32 msg;
+} __packed;
+
+#define MHI_DTR_CTRL_MAGIC	0x4C525443	/* 'CTRL' */
+#define MHI_DTR_MSG_DTR		BIT(0)
+#define MHI_DTR_MSG_RTS		BIT(1)
+#define MHI_DTR_HOST_STATE	0x10
+
+/* Per-controller IP_CTRL channel, used to signal DTR/RTS to that modem */
+struct mhi_wwan_dtr {
+	struct mhi_controller *cntrl;
+	struct mhi_device *mhi_dev;
+	struct list_head node;
+	u8 rx_buf[sizeof(struct mhi_dtr_ctrl_msg)]; /* sink for modem serial-state DL */
+};
+
+static LIST_HEAD(mhi_wwan_dtr_list);
+static DEFINE_MUTEX(mhi_wwan_dtr_lock);
+
 struct mhi_wwan_dev {
 	/* Lower level is a mhi dev, upper level is a wwan port */
 	struct mhi_device *mhi_dev;
@@ -103,6 +132,61 @@ static void mhi_wwan_ctrl_refill_work(struct work_struct *work)
 	}
 }
 
+/* Signal the modem's DTR/RTS lines over its own controller's IP_CTRL channel */
+static int mhi_wwan_ctrl_send_dtr(struct mhi_wwan_dev *mhiwwan, unsigned int mdmbits)
+{
+	struct mhi_controller *cntrl = mhiwwan->mhi_dev->mhi_cntrl;
+	struct mhi_device *ctrl_dev = NULL;
+	struct mhi_dtr_ctrl_msg *dtr_msg;
+	struct mhi_wwan_dtr *dtr;
+	u32 msg = 0;
+	int ret;
+
+	guard(mutex)(&mhi_wwan_dtr_lock);
+
+	list_for_each_entry(dtr, &mhi_wwan_dtr_list, node) {
+		if (dtr->cntrl == cntrl) {
+			ctrl_dev = dtr->mhi_dev;
+			break;
+		}
+	}
+	if (!ctrl_dev) {
+		dev_dbg(&mhiwwan->mhi_dev->dev,
+			"IP_CTRL not enumerated; DTR/RTS not signalled to modem\n");
+		return 0;
+	}
+
+	dtr_msg = kzalloc_obj(*dtr_msg);
+	if (!dtr_msg)
+		return -ENOMEM;
+
+	if (mdmbits & TIOCM_DTR)
+		msg |= MHI_DTR_MSG_DTR;
+	if (mdmbits & TIOCM_RTS)
+		msg |= MHI_DTR_MSG_RTS;
+
+	dtr_msg->preamble = cpu_to_le32(MHI_DTR_CTRL_MAGIC);
+	dtr_msg->msg_id = cpu_to_le32(MHI_DTR_HOST_STATE);
+	dtr_msg->dest_id = cpu_to_le32(mhiwwan->mhi_dev->ul_chan_id);
+	dtr_msg->size = cpu_to_le32(sizeof(__le32));
+	dtr_msg->msg = cpu_to_le32(msg);
+
+	ret = mhi_queue_buf(ctrl_dev, DMA_TO_DEVICE, dtr_msg, sizeof(*dtr_msg),
+			    MHI_EOT);
+	if (ret) {
+		dev_dbg(&mhiwwan->mhi_dev->dev,
+			"failed to queue DTR/RTS signal: %d\n", ret);
+		kfree(dtr_msg);
+	}
+
+	return ret;
+}
+
+static void mhi_wwan_ctrl_dtr_rts(struct wwan_port *port, unsigned int mdmbits)
+{
+	mhi_wwan_ctrl_send_dtr(wwan_port_get_drvdata(port), mdmbits);
+}
+
 static int mhi_wwan_ctrl_start(struct wwan_port *port)
 {
 	struct mhi_wwan_dev *mhiwwan = wwan_port_get_drvdata(port);
@@ -163,6 +247,7 @@ static const struct wwan_port_ops wwan_pops = {
 	.start = mhi_wwan_ctrl_start,
 	.stop = mhi_wwan_ctrl_stop,
 	.tx = mhi_wwan_ctrl_tx,
+	.dtr_rts = mhi_wwan_ctrl_dtr_rts,
 };
 
 static void mhi_ul_xfer_cb(struct mhi_device *mhi_dev,
@@ -255,6 +340,71 @@ static void mhi_wwan_ctrl_remove(struct mhi_device *mhi_dev)
 	kfree(mhiwwan);
 }
 
+/* IP_CTRL channel driver, bound separately so the data-port path is untouched */
+static void mhi_wwan_dtr_ul_xfer_cb(struct mhi_device *mhi_dev,
+				    struct mhi_result *mhi_result)
+{
+	/* MHI core has done with the buffer, release it */
+	kfree(mhi_result->buf_addr);
+}
+
+static void mhi_wwan_dtr_dl_xfer_cb(struct mhi_device *mhi_dev,
+				    struct mhi_result *mhi_result)
+{
+	struct mhi_wwan_dtr *dtr = dev_get_drvdata(&mhi_dev->dev);
+
+	/* Modem serial state not needed; requeue the sink buffer to keep DL ring live */
+	mhi_queue_buf(mhi_dev, DMA_FROM_DEVICE, dtr->rx_buf,
+		      sizeof(dtr->rx_buf), MHI_EOT);
+}
+
+static int mhi_wwan_dtr_probe(struct mhi_device *mhi_dev,
+			      const struct mhi_device_id *id)
+{
+	struct mhi_wwan_dtr *dtr;
+	int ret;
+
+	dtr = kzalloc_obj(*dtr);
+	if (!dtr)
+		return -ENOMEM;
+
+	ret = mhi_prepare_for_transfer(mhi_dev);
+	if (ret) {
+		kfree(dtr);
+		return ret;
+	}
+
+	dtr->cntrl = mhi_dev->mhi_cntrl;
+	dtr->mhi_dev = mhi_dev;
+	dev_set_drvdata(&mhi_dev->dev, dtr);
+
+	ret = mhi_queue_buf(mhi_dev, DMA_FROM_DEVICE, dtr->rx_buf,
+			    sizeof(dtr->rx_buf), MHI_EOT);
+	if (ret) {
+		mhi_unprepare_from_transfer(mhi_dev);
+		kfree(dtr);
+		return ret;
+	}
+
+	mutex_lock(&mhi_wwan_dtr_lock);
+	list_add(&dtr->node, &mhi_wwan_dtr_list);
+	mutex_unlock(&mhi_wwan_dtr_lock);
+
+	return 0;
+}
+
+static void mhi_wwan_dtr_remove(struct mhi_device *mhi_dev)
+{
+	struct mhi_wwan_dtr *dtr = dev_get_drvdata(&mhi_dev->dev);
+
+	mutex_lock(&mhi_wwan_dtr_lock);
+	list_del(&dtr->node);
+	mutex_unlock(&mhi_wwan_dtr_lock);
+
+	mhi_unprepare_from_transfer(mhi_dev);
+	kfree(dtr);
+}
+
 static const struct mhi_device_id mhi_wwan_ctrl_match_table[] = {
 	{ .chan = "DUN", .driver_data = WWAN_PORT_AT },
 	{ .chan = "DUN2", .driver_data = WWAN_PORT_AT },
@@ -278,7 +428,45 @@ static struct mhi_driver mhi_wwan_ctrl_driver = {
 	},
 };
 
-module_mhi_driver(mhi_wwan_ctrl_driver);
+static const struct mhi_device_id mhi_wwan_dtr_match_table[] = {
+	{ .chan = "IP_CTRL" },
+	{},
+};
+MODULE_DEVICE_TABLE(mhi, mhi_wwan_dtr_match_table);
+
+static struct mhi_driver mhi_wwan_dtr_driver = {
+	.id_table = mhi_wwan_dtr_match_table,
+	.remove = mhi_wwan_dtr_remove,
+	.probe = mhi_wwan_dtr_probe,
+	.ul_xfer_cb = mhi_wwan_dtr_ul_xfer_cb,
+	.dl_xfer_cb = mhi_wwan_dtr_dl_xfer_cb,
+	.driver = {
+		.name = "mhi_wwan_dtr",
+	},
+};
+
+static int __init mhi_wwan_ctrl_init(void)
+{
+	int ret;
+
+	ret = mhi_driver_register(&mhi_wwan_dtr_driver);
+	if (ret)
+		return ret;
+
+	ret = mhi_driver_register(&mhi_wwan_ctrl_driver);
+	if (ret)
+		mhi_driver_unregister(&mhi_wwan_dtr_driver);
+
+	return ret;
+}
+module_init(mhi_wwan_ctrl_init);
+
+static void __exit mhi_wwan_ctrl_exit(void)
+{
+	mhi_driver_unregister(&mhi_wwan_ctrl_driver);
+	mhi_driver_unregister(&mhi_wwan_dtr_driver);
+}
+module_exit(mhi_wwan_ctrl_exit);
 
 MODULE_LICENSE("GPL v2");
 MODULE_DESCRIPTION("MHI WWAN CTRL Driver");
diff --git a/drivers/net/wwan/wwan_core.c b/drivers/net/wwan/wwan_core.c
index ffbcf11e4e681..3a6a0c5a3acf4 100644
--- a/drivers/net/wwan/wwan_core.c
+++ b/drivers/net/wwan/wwan_core.c
@@ -685,6 +685,12 @@ void wwan_remove_port(struct wwan_port *port)
 
 	mutex_lock(&port->ops_lock);
 	if (port->start_count) {
+		if (port->type == WWAN_PORT_AT && port->ops->dtr_rts) {
+			mutex_lock(&port->data_lock);
+			port->at_data.mdmbits &= ~(TIOCM_DTR | TIOCM_RTS);
+			mutex_unlock(&port->data_lock);
+			port->ops->dtr_rts(port, 0);
+		}
 		port->ops->stop(port);
 		port->start_count = 0;
 	}
@@ -759,8 +765,17 @@ static int wwan_port_op_start(struct wwan_port *port)
 	if (!port->start_count)
 		ret = port->ops->start(port);
 
-	if (!ret)
+	if (!ret) {
 		port->start_count++;
+		/* Mirror TTY semantics: raise DTR/RTS on first open of an AT port */
+		if (port->start_count == 1 && port->type == WWAN_PORT_AT &&
+		    port->ops->dtr_rts) {
+			mutex_lock(&port->data_lock);
+			port->at_data.mdmbits |= TIOCM_DTR | TIOCM_RTS;
+			mutex_unlock(&port->data_lock);
+			port->ops->dtr_rts(port, port->at_data.mdmbits);
+		}
+	}
 
 out_unlock:
 	mutex_unlock(&port->ops_lock);
@@ -773,6 +788,13 @@ static void wwan_port_op_stop(struct wwan_port *port)
 	mutex_lock(&port->ops_lock);
 	port->start_count--;
 	if (!port->start_count) {
+		/* Mirror TTY semantics: drop DTR/RTS on last close of an AT port */
+		if (port->ops && port->type == WWAN_PORT_AT && port->ops->dtr_rts) {
+			mutex_lock(&port->data_lock);
+			port->at_data.mdmbits &= ~(TIOCM_DTR | TIOCM_RTS);
+			mutex_unlock(&port->data_lock);
+			port->ops->dtr_rts(port, port->at_data.mdmbits);
+		}
 		if (port->ops)
 			port->ops->stop(port);
 		skb_queue_purge(&port->rxq);
@@ -980,6 +1002,7 @@ static long wwan_port_fops_at_ioctl(struct wwan_port *port, unsigned int cmd,
 				    unsigned long arg)
 {
 	int ret = 0;
+	bool call_dtr_rts = false;
 
 	mutex_lock(&port->data_lock);
 
@@ -1036,6 +1059,8 @@ static long wwan_port_fops_at_ioctl(struct wwan_port *port, unsigned int cmd,
 			port->at_data.mdmbits |= mdmbits;
 		else
 			port->at_data.mdmbits = mdmbits;
+		if (port->type == WWAN_PORT_AT)
+			call_dtr_rts = true;
 		break;
 	}
 
@@ -1061,6 +1086,19 @@ static long wwan_port_fops_at_ioctl(struct wwan_port *port, unsigned int cmd,
 
 	mutex_unlock(&port->data_lock);
 
+	if (call_dtr_rts) {
+		unsigned int bits;
+
+		mutex_lock(&port->ops_lock);
+		if (port->ops && port->ops->dtr_rts) {
+			mutex_lock(&port->data_lock);
+			bits = port->at_data.mdmbits;
+			mutex_unlock(&port->data_lock);
+			port->ops->dtr_rts(port, bits);
+		}
+		mutex_unlock(&port->ops_lock);
+	}
+
 	return ret;
 }
 
diff --git a/include/linux/wwan.h b/include/linux/wwan.h
index 1e0e2cb535799..57406139304ea 100644
--- a/include/linux/wwan.h
+++ b/include/linux/wwan.h
@@ -57,6 +57,8 @@ struct wwan_port;
  * @tx_blocking: Optional blocking routine that sends WWAN port protocol data
  *               to the device.
  * @tx_poll: Optional routine that sets additional TX poll flags.
+ * @dtr_rts: Optional routine that updates the modem control lines to match
+ *           @mdmbits (a TIOCM_* bitmask). Only called for WWAN_PORT_AT ports.
  *
  * The wwan_port_ops structure contains a list of low-level operations
  * that control a WWAN port device. All functions are mandatory unless specified.
@@ -70,6 +72,7 @@ struct wwan_port_ops {
 	int (*tx_blocking)(struct wwan_port *port, struct sk_buff *skb);
 	__poll_t (*tx_poll)(struct wwan_port *port, struct file *filp,
 			    poll_table *wait);
+	void (*dtr_rts)(struct wwan_port *port, unsigned int mdmbits);
 };
 
 /** struct wwan_port_caps - The WWAN port capbilities

gemini-3.1-pro-preview

null

null

							input: 6795
							output: 20
							thoughts: 423
						

**Analyzing the MHI WWAN DTR/RTS Patch**

Okay, so I'm looking at this patch that adds DTR/RTS signaling support for MHI WWAN control ports over the IP_CTRL channel. They've updated a few key files: `pci_generic.c`, `mhi_wwan_ctrl.c`, `wwan_core.c`, and `wwan.h`. Looks like they've added a `dtr_rts` callback to the `wwan_port_ops` struct, and they've implemented `mhi_wwan_ctrl_dtr_rts` specifically within `mhi_wwan_ctrl.c`. They're also introducing a new MHI driver, `mhi_wwan_dtr_driver`, which binds to the "IP_CTRL" channel. And, finally, `wwan_core.c` is being modified to call the `dtr_rts` function during open/close operations and for certain TIOCM* ioctls.

My initial thought is to figure out how easily we can test this in a virtualized environment. The WWAN core is accessible via `/dev/wwan*` character devices, which is helpful. The MHI WWAN control driver is an MHI driver, which sits on top of the MHI bus used by Qualcomm modems, typically connected via PCIe. The critical question here is, can we emulate or fuzz MHI devices effectively? Syzkaller has some WWAN support, but MHI devices are usually physical PCIe devices, which will be a problem.

Wait a minute, since syzkaller is able to fuzz the `/dev/wwan*` interfaces, we just need to figure out how to create a WWAN port in a virtual environment without a physical MHI device. I need to see if there's any support for creating software-based WWAN ports. For example, `mac80211_hwsim` provides a virtual WiFi device, `vkms` gives us a virtual DRM, and `vhci` supports virtual bluetooth. Is there something similar for WWAN? Time to look for callers of `wwan_create_port`.

{
  "Expression": "wwan_create_port"
}

{
  "Output": "drivers/net/wwan/iosm/iosm_ipc_port.c=48=struct iosm_cdev *ipc_port_init(struct iosm_imem *ipc_imem,\n--\ndrivers/net/wwan/iosm/iosm_ipc_port.c-64-\ndrivers/net/wwan/iosm/iosm_ipc_port.c:65:\tipc_port-\u003eiosm_port = wwan_create_port(ipc_port-\u003edev, port_type,\ndrivers/net/wwan/iosm/iosm_ipc_port.c-66-\t\t\t\t\t       \u0026ipc_wwan_ctrl_ops, NULL,\n--\ndrivers/net/wwan/mhi_wwan_ctrl.c=298=static int mhi_wwan_ctrl_probe(struct mhi_device *mhi_dev,\n--\ndrivers/net/wwan/mhi_wwan_ctrl.c-322-\t/* Register as a wwan port, id-\u003edriver_data contains wwan port type */\ndrivers/net/wwan/mhi_wwan_ctrl.c:323:\tport = wwan_create_port(\u0026cntrl-\u003emhi_dev-\u003edev, id-\u003edriver_data,\ndrivers/net/wwan/mhi_wwan_ctrl.c-324-\t\t\t\t\u0026wwan_pops, NULL, mhiwwan);\n--\ndrivers/net/wwan/rpmsg_wwan_ctrl.c=112=static int rpmsg_wwan_ctrl_probe(struct rpmsg_device *rpdev)\n--\ndrivers/net/wwan/rpmsg_wwan_ctrl.c-129-\t/* Register as a wwan port, id.driver_data contains wwan port type */\ndrivers/net/wwan/rpmsg_wwan_ctrl.c:130:\tport = wwan_create_port(parent, rpdev-\u003eid.driver_data,\ndrivers/net/wwan/rpmsg_wwan_ctrl.c-131-\t\t\t\t\u0026rpmsg_wwan_pops, NULL, rpwwan);\n--\ndrivers/net/wwan/t7xx/t7xx_port_wwan.c=153=static void t7xx_port_wwan_create(struct t7xx_port *port)\n--\ndrivers/net/wwan/t7xx/t7xx_port_wwan.c-162-\t\tcaps.headroom_len = header_len;\ndrivers/net/wwan/t7xx/t7xx_port_wwan.c:163:\t\tport-\u003ewwan.wwan_port = wwan_create_port(port-\u003edev, port_conf-\u003eport_type,\ndrivers/net/wwan/t7xx/t7xx_port_wwan.c-164-\t\t\t\t\t\t\t\u0026wwan_ops, \u0026caps, port);\n--\ndrivers/net/wwan/wwan_core.c=222=EXPORT_SYMBOL_GPL(wwan_put_debugfs_dir);\n--\ndrivers/net/wwan/wwan_core.c-227- * This function is not exported (for now), it is called indirectly via\ndrivers/net/wwan/wwan_core.c:228: * wwan_create_port().\ndrivers/net/wwan/wwan_core.c-229- */\n--\ndrivers/net/wwan/wwan_core.c=617=static void wwan_port_unregister_gnss(struct wwan_port *port)\n--\ndrivers/net/wwan/wwan_core.c-622-\ndrivers/net/wwan/wwan_core.c:623:struct wwan_port *wwan_create_port(struct device *parent,\ndrivers/net/wwan/wwan_core.c-624-\t\t\t\t   enum wwan_port_type type,\n--\ndrivers/net/wwan/wwan_core.c-679-}\ndrivers/net/wwan/wwan_core.c:680:EXPORT_SYMBOL_GPL(wwan_create_port);\ndrivers/net/wwan/wwan_core.c-681-\n--\ndrivers/net/wwan/wwan_hwsim.c=303=static struct wwan_hwsim_port *wwan_hwsim_port_new(struct wwan_hwsim_dev *dev,\n--\ndrivers/net/wwan/wwan_hwsim.c-329-\ndrivers/net/wwan/wwan_hwsim.c:330:\tport-\u003ewwan = wwan_create_port(\u0026dev-\u003edev, type, ops, NULL, port);\ndrivers/net/wwan/wwan_hwsim.c-331-\tif (IS_ERR(port-\u003ewwan)) {\n--\ndrivers/usb/class/cdc-wdm.c=929=static void wdm_wwan_init(struct wdm_device *desc)\n--\ndrivers/usb/class/cdc-wdm.c-939-\ndrivers/usb/class/cdc-wdm.c:940:\tport = wwan_create_port(\u0026intf-\u003edev, desc-\u003ewwanp_type, \u0026wdm_wwan_port_ops,\ndrivers/usb/class/cdc-wdm.c-941-\t\t\t\tNULL, desc);\n--\ninclude/linux/wwan.h=82=struct wwan_port_caps {\n--\ninclude/linux/wwan.h-87-/**\ninclude/linux/wwan.h:88: * wwan_create_port - Add a new WWAN port\ninclude/linux/wwan.h-89- * @parent: Device to use as parent and shared by all WWAN ports\n--\ninclude/linux/wwan.h-106- */\ninclude/linux/wwan.h:107:struct wwan_port *wwan_create_port(struct device *parent,\ninclude/linux/wwan.h-108-\t\t\t\t   enum wwan_port_type type,\n"
}

gemini-3.1-pro-preview

null

null

							input: 9191
							output: 20
							thoughts: 416
						

**Fuzzing the WWAN Subsystem**

Okay, so I see `drivers/net/wwan/wwan_hwsim.c`. That's interesting, maybe I can use this to fuzz `wwan_core.c`. Let's see... Hmm, the patch modifies both `wwan_core.c` and `mhi_wwan_ctrl.c`. Interesting. Looking at the `wwan_core.c` changes, specifically that snippet... it seems like there's a new check and potential call to `dtr_rts` within `wwan_remove_port` if the port type is `WWAN_PORT_AT`.

This looks like a potential path reachable from the `wwan_hwsim` driver, provided it creates a `WWAN_PORT_AT` port. But wait... `wwan_hwsim` itself doesn't implement the `dtr_rts` callback function. So that means, if `wwan_hwsim` creates a port, `port->ops->dtr_rts` will be NULL.

Okay, so if the `dtr_rts` call is happening, it means the `mhi_wwan_ctrl.c` driver is involved. But that driver requires an MHI device. The question is, can I fuzz `mhi_wwan_ctrl` directly? Or is there a software emulator for MHI devices? That's what I need to figure out next.

{
  "Expression": "mhi_.*_probe"
}

{
  "Output": "drivers/bus/mhi/ep/main.c=1598=EXPORT_SYMBOL_GPL(mhi_ep_unregister_controller);\ndrivers/bus/mhi/ep/main.c-1599-\ndrivers/bus/mhi/ep/main.c:1600:static int mhi_ep_probe(struct device *dev)\ndrivers/bus/mhi/ep/main.c-1601-{\n--\ndrivers/bus/mhi/ep/main.c=1703=const struct bus_type mhi_ep_bus_type = {\n--\ndrivers/bus/mhi/ep/main.c-1707-\t.uevent = mhi_ep_uevent,\ndrivers/bus/mhi/ep/main.c:1708:\t.probe = mhi_ep_probe,\ndrivers/bus/mhi/ep/main.c-1709-\t.remove = mhi_ep_remove,\n--\ndrivers/bus/mhi/host/pci_generic.c=1329=static int mhi_pci_generic_edl_trigger(struct mhi_controller *mhi_cntrl)\n--\ndrivers/bus/mhi/host/pci_generic.c-1362-\ndrivers/bus/mhi/host/pci_generic.c:1363:static int mhi_pci_probe(struct pci_dev *pdev, const struct pci_device_id *id)\ndrivers/bus/mhi/host/pci_generic.c-1364-{\n--\ndrivers/bus/mhi/host/pci_generic.c=1764=static struct pci_driver mhi_pci_driver = {\n--\ndrivers/bus/mhi/host/pci_generic.c-1766-\t.id_table\t= mhi_pci_id_table,\ndrivers/bus/mhi/host/pci_generic.c:1767:\t.probe\t\t= mhi_pci_probe,\ndrivers/bus/mhi/host/pci_generic.c-1768-\t.remove\t\t= mhi_pci_remove,\n--\ndrivers/net/mhi_net.c=335=static void mhi_net_dellink(struct mhi_device *mhi_dev, struct net_device *ndev)\n--\ndrivers/net/mhi_net.c-349-\ndrivers/net/mhi_net.c:350:static int mhi_net_probe(struct mhi_device *mhi_dev,\ndrivers/net/mhi_net.c-351-\t\t\t const struct mhi_device_id *id)\n--\ndrivers/net/mhi_net.c=397=static struct mhi_driver mhi_net_driver = {\ndrivers/net/mhi_net.c:398:\t.probe = mhi_net_probe,\ndrivers/net/mhi_net.c-399-\t.remove = mhi_net_remove,\n--\ndrivers/net/wwan/mhi_wwan_ctrl.c=273=static void mhi_dl_xfer_cb(struct mhi_device *mhi_dev,\n--\ndrivers/net/wwan/mhi_wwan_ctrl.c-297-\ndrivers/net/wwan/mhi_wwan_ctrl.c:298:static int mhi_wwan_ctrl_probe(struct mhi_device *mhi_dev,\ndrivers/net/wwan/mhi_wwan_ctrl.c-299-\t\t\t       const struct mhi_device_id *id)\n--\ndrivers/net/wwan/mhi_wwan_ctrl.c=351=static void mhi_wwan_dtr_dl_xfer_cb(struct mhi_device *mhi_dev,\n--\ndrivers/net/wwan/mhi_wwan_ctrl.c-360-\ndrivers/net/wwan/mhi_wwan_ctrl.c:361:static int mhi_wwan_dtr_probe(struct mhi_device *mhi_dev,\ndrivers/net/wwan/mhi_wwan_ctrl.c-362-\t\t\t      const struct mhi_device_id *id)\n--\ndrivers/net/wwan/mhi_wwan_ctrl.c=420=static struct mhi_driver mhi_wwan_ctrl_driver = {\n--\ndrivers/net/wwan/mhi_wwan_ctrl.c-422-\t.remove = mhi_wwan_ctrl_remove,\ndrivers/net/wwan/mhi_wwan_ctrl.c:423:\t.probe = mhi_wwan_ctrl_probe,\ndrivers/net/wwan/mhi_wwan_ctrl.c-424-\t.ul_xfer_cb = mhi_ul_xfer_cb,\n--\ndrivers/net/wwan/mhi_wwan_ctrl.c=437=static struct mhi_driver mhi_wwan_dtr_driver = {\n--\ndrivers/net/wwan/mhi_wwan_ctrl.c-439-\t.remove = mhi_wwan_dtr_remove,\ndrivers/net/wwan/mhi_wwan_ctrl.c:440:\t.probe = mhi_wwan_dtr_probe,\ndrivers/net/wwan/mhi_wwan_ctrl.c-441-\t.ul_xfer_cb = mhi_wwan_dtr_ul_xfer_cb,\n--\ndrivers/net/wwan/mhi_wwan_mbim.c=599=static const struct wwan_ops mhi_mbim_wwan_ops = {\n--\ndrivers/net/wwan/mhi_wwan_mbim.c-605-\ndrivers/net/wwan/mhi_wwan_mbim.c:606:static int mhi_mbim_probe(struct mhi_device *mhi_dev, const struct mhi_device_id *id)\ndrivers/net/wwan/mhi_wwan_mbim.c-607-{\n--\ndrivers/net/wwan/mhi_wwan_mbim.c=654=static struct mhi_driver mhi_mbim_driver = {\ndrivers/net/wwan/mhi_wwan_mbim.c:655:\t.probe = mhi_mbim_probe,\ndrivers/net/wwan/mhi_wwan_mbim.c-656-\t.remove = mhi_mbim_remove,\n--\nnet/qrtr/mhi.c=86=static int qcom_mhi_qrtr_queue_dl_buffers(struct mhi_device *mhi_dev)\n--\nnet/qrtr/mhi.c-108-\nnet/qrtr/mhi.c:109:static int qcom_mhi_qrtr_probe(struct mhi_device *mhi_dev,\nnet/qrtr/mhi.c-110-\t\t\t       const struct mhi_device_id *id)\n--\nnet/qrtr/mhi.c=212=static struct mhi_driver qcom_mhi_qrtr_driver = {\nnet/qrtr/mhi.c:213:\t.probe = qcom_mhi_qrtr_probe,\nnet/qrtr/mhi.c-214-\t.remove = qcom_mhi_qrtr_remove,\n"
}

gemini-3.1-pro-preview

null

null

							input: 11818
							output: 21
							thoughts: 114
						

**Fuzzing the MHI PCI Driver: A Quick Assessment**

Okay, so I'm looking at this `mhi_pci_generic.c` driver, which from what I can tell, handles the MHI bus via PCI. That immediately triggers a thought: PCI drivers are often good candidates for fuzzing. The key question is whether this one has a strong dependency on specific hardware behavior that's not easily emulated. I know syzkaller has some PCI fuzzing capabilities, maybe using something like `syz_pci_device`, though my experience is that it can be a bit limited.

The real crux of it is this: does `mhi_pci_generic` *need* a real, physical device to function? If not, then we might be able to get some mileage fuzzing it. Let me just quickly check `mhi_pci_probe` and see if anything jumps out at me. That should give me a good initial idea of the hardware dependencies.

{
  "Expression": "mhi_pci_probe"
}

{
  "Output": "drivers/bus/mhi/host/pci_generic.c=1329=static int mhi_pci_generic_edl_trigger(struct mhi_controller *mhi_cntrl)\n--\ndrivers/bus/mhi/host/pci_generic.c-1362-\ndrivers/bus/mhi/host/pci_generic.c:1363:static int mhi_pci_probe(struct pci_dev *pdev, const struct pci_device_id *id)\ndrivers/bus/mhi/host/pci_generic.c-1364-{\n--\ndrivers/bus/mhi/host/pci_generic.c=1764=static struct pci_driver mhi_pci_driver = {\n--\ndrivers/bus/mhi/host/pci_generic.c-1766-\t.id_table\t= mhi_pci_id_table,\ndrivers/bus/mhi/host/pci_generic.c:1767:\t.probe\t\t= mhi_pci_probe,\ndrivers/bus/mhi/host/pci_generic.c-1768-\t.remove\t\t= mhi_pci_remove,\n"
}

gemini-3.1-pro-preview

null

null

							input: 12473
							output: 45
							thoughts: 23
						

Here's a summary of my thought process:

**Diving into `mhi_pci_probe` for Fuzzing Potential**

Okay, time to take a look at `mhi_pci_probe`. My primary goal here is to determine if this function is a viable candidate for fuzzing. I need to quickly assess it for potential vulnerabilities that can be exploited, and fuzzing is a great way to expose them. I’m thinking about what kinds of inputs it takes, how those inputs are handled, and if there are any obvious areas where unexpected data could lead to crashes or undesirable behavior. Does it deal with data from potentially untrusted sources? Does it have any complex conditional logic that could be bypassed with the right inputs? Is there memory allocation and deallocation involved that could lead to memory corruption issues? Let's get to it and see what we can find.

{
  "File": "drivers/bus/mhi/host/pci_generic.c",
  "FirstLine": 1363,
  "LineCount": 100
}

{
  "Contents": "1363:\tstatic int mhi_pci_probe(struct pci_dev *pdev, const struct pci_device_id *id)\n1364:\t{\n1365:\t\tconst struct mhi_pci_dev_info *info = (struct mhi_pci_dev_info *) id-\u003edriver_data;\n1366:\t\tconst struct mhi_controller_config *mhi_cntrl_config;\n1367:\t\tstruct mhi_pci_device *mhi_pdev;\n1368:\t\tstruct mhi_controller *mhi_cntrl;\n1369:\t\tunsigned int dma_data_width;\n1370:\t\tint err;\n1371:\t\n1372:\t\tdev_info(\u0026pdev-\u003edev, \"MHI PCI device found: %s\\n\", info-\u003ename);\n1373:\t\n1374:\t\t/* mhi_pdev.mhi_cntrl must be zero-initialized */\n1375:\t\tmhi_pdev = devm_kzalloc(\u0026pdev-\u003edev, sizeof(*mhi_pdev), GFP_KERNEL);\n1376:\t\tif (!mhi_pdev)\n1377:\t\t\treturn -ENOMEM;\n1378:\t\n1379:\t\tINIT_WORK(\u0026mhi_pdev-\u003erecovery_work, mhi_pci_recovery_work);\n1380:\t\n1381:\t\tif (pdev-\u003eis_virtfn \u0026\u0026 info-\u003evf_config)\n1382:\t\t\tmhi_cntrl_config = info-\u003evf_config;\n1383:\t\telse\n1384:\t\t\tmhi_cntrl_config = info-\u003econfig;\n1385:\t\n1386:\t\t/* Initialize health check monitor only for Physical functions */\n1387:\t\tif (!pdev-\u003eis_virtfn)\n1388:\t\t\ttimer_setup(\u0026mhi_pdev-\u003ehealth_check_timer, health_check, 0);\n1389:\t\n1390:\t\tmhi_cntrl = \u0026mhi_pdev-\u003emhi_cntrl;\n1391:\t\n1392:\t\tdma_data_width = (pdev-\u003eis_virtfn \u0026\u0026 info-\u003evf_dma_data_width) ?\n1393:\t\t\t\t  info-\u003evf_dma_data_width : info-\u003edma_data_width;\n1394:\t\n1395:\t\tmhi_cntrl-\u003ecntrl_dev = \u0026pdev-\u003edev;\n1396:\t\tmhi_cntrl-\u003eiova_start = 0;\n1397:\t\tmhi_cntrl-\u003eiova_stop = (dma_addr_t)DMA_BIT_MASK(dma_data_width);\n1398:\t\tmhi_cntrl-\u003efw_image = info-\u003efw;\n1399:\t\tmhi_cntrl-\u003eedl_image = info-\u003eedl;\n1400:\t\n1401:\t\tmhi_cntrl-\u003eread_reg = mhi_pci_read_reg;\n1402:\t\tmhi_cntrl-\u003ewrite_reg = mhi_pci_write_reg;\n1403:\t\tmhi_cntrl-\u003estatus_cb = mhi_pci_status_cb;\n1404:\t\tmhi_cntrl-\u003eruntime_get = mhi_pci_runtime_get;\n1405:\t\tmhi_cntrl-\u003eruntime_put = mhi_pci_runtime_put;\n1406:\t\tmhi_cntrl-\u003emru = info-\u003emru_default;\n1407:\t\tmhi_cntrl-\u003ename = info-\u003ename;\n1408:\t\n1409:\t\tif (!pdev-\u003eis_virtfn)\n1410:\t\t\tmhi_pdev-\u003ereset_on_remove = info-\u003ereset_on_remove;\n1411:\t\n1412:\t\tif (info-\u003eedl_trigger)\n1413:\t\t\tmhi_cntrl-\u003eedl_trigger = mhi_pci_generic_edl_trigger;\n1414:\t\n1415:\t\tif (info-\u003esideband_wake) {\n1416:\t\t\tmhi_cntrl-\u003ewake_get = mhi_pci_wake_get_nop;\n1417:\t\t\tmhi_cntrl-\u003ewake_put = mhi_pci_wake_put_nop;\n1418:\t\t\tmhi_cntrl-\u003ewake_toggle = mhi_pci_wake_toggle_nop;\n1419:\t\t}\n1420:\t\n1421:\t\terr = mhi_pci_claim(mhi_cntrl, info-\u003ebar_num, DMA_BIT_MASK(dma_data_width));\n1422:\t\tif (err)\n1423:\t\t\treturn err;\n1424:\t\n1425:\t\terr = mhi_pci_get_irqs(mhi_cntrl, mhi_cntrl_config);\n1426:\t\tif (err)\n1427:\t\t\treturn err;\n1428:\t\n1429:\t\tpci_set_drvdata(pdev, mhi_pdev);\n1430:\t\n1431:\t\t/* Have stored pci confspace at hand for restore in sudden PCI error.\n1432:\t\t * cache the state locally and discard the PCI core one.\n1433:\t\t */\n1434:\t\tpci_save_state(pdev);\n1435:\t\tmhi_pdev-\u003epci_state = pci_store_saved_state(pdev);\n1436:\t\tpci_load_saved_state(pdev, NULL);\n1437:\t\n1438:\t\terr = mhi_register_controller(mhi_cntrl, mhi_cntrl_config);\n1439:\t\tif (err)\n1440:\t\t\treturn err;\n1441:\t\n1442:\t\t/* MHI bus does not power up the controller by default */\n1443:\t\terr = mhi_prepare_for_power_up(mhi_cntrl);\n1444:\t\tif (err) {\n1445:\t\t\tdev_err(\u0026pdev-\u003edev, \"failed to prepare MHI controller\\n\");\n1446:\t\t\tgoto err_unregister;\n1447:\t\t}\n1448:\t\n1449:\t\terr = mhi_async_power_up(mhi_cntrl);\n1450:\t\tif (err) {\n1451:\t\t\tdev_err(\u0026pdev-\u003edev, \"failed to power up MHI controller\\n\");\n1452:\t\t\tgoto err_unprepare;\n1453:\t\t}\n1454:\t\n1455:\t\tset_bit(MHI_PCI_DEV_STARTED, \u0026mhi_pdev-\u003estatus);\n1456:\t\n1457:\t\t/* start health check */\n1458:\t\tif (!pdev-\u003eis_virtfn)\n1459:\t\t\tmod_timer(\u0026mhi_pdev-\u003ehealth_check_timer, jiffies + HEALTH_CHECK_PERIOD);\n1460:\t\n1461:\t\t/* Allow runtime suspend only if both PME from D3Hot and M3 are supported */\n1462:\t\tif (pci_pme_capable(pdev, PCI_D3hot) \u0026\u0026 !(info-\u003eno_m3)) {\n"
}

gemini-3.1-pro-preview

null

null

							input: 14603
							output: 22
							thoughts: 112
						

**Analyzing the MHI PCI Probe Process**

Okay, so `mhi_pci_probe` is the starting point. It looks like it kicks off a chain of events: `mhi_register_controller`, `mhi_prepare_for_power_up`, and then `mhi_async_power_up`.  This is a PCI driver, which means we're dealing with PCI devices, and the system is using the `mhi_pci_generic` driver. The intriguing part is the mention of Syzkaller's `syz_pci_device` which suggests this might be easily reproducible with fuzzing.

Now, my main concern is `mhi_async_power_up`. As an expert in this area, my first thought is whether this function involves more than just a simple power-on sequence. Does it require some complex hardware interaction that goes beyond the typical PCI device initialization? This warrants a deeper look. I need to understand if there are any subtle race conditions, hardware-specific quirks, or dependencies on other system components within that function. I should check `mhi_async_power_up` to verify.

{
  "Expression": "mhi_async_power_up"
}

{
  "Output": "drivers/accel/qaic/mhi_controller.c=800=static int mhi_reset_and_async_power_up(struct mhi_controller *mhi_cntrl)\n--\ndrivers/accel/qaic/mhi_controller.c-819-\tif (current_ee == MHI_EE_PBL)\ndrivers/accel/qaic/mhi_controller.c:820:\t\tret = mhi_async_power_up(mhi_cntrl);\ndrivers/accel/qaic/mhi_controller.c-821-\telse\n--\ndrivers/accel/qaic/mhi_controller.c=827=struct mhi_controller *qaic_mhi_register_controller(struct pci_dev *pci_dev, void __iomem *mhi_bar,\n--\ndrivers/accel/qaic/mhi_controller.c-887-\ndrivers/accel/qaic/mhi_controller.c:888:\tret = mhi_async_power_up(mhi_cntrl);\ndrivers/accel/qaic/mhi_controller.c-889-\t/*\n--\ndrivers/accel/qaic/mhi_controller.c-898-\tif (ret) {\ndrivers/accel/qaic/mhi_controller.c:899:\t\tpci_err(pci_dev, \"mhi_async_power_up failed %d\\n\", ret);\ndrivers/accel/qaic/mhi_controller.c-900-\t\tgoto power_up_fail;\n--\ndrivers/accel/qaic/mhi_controller.c=924=void qaic_mhi_reset_done(struct mhi_controller *mhi_cntrl)\n--\ndrivers/accel/qaic/mhi_controller.c-928-\ndrivers/accel/qaic/mhi_controller.c:929:\tret = mhi_async_power_up(mhi_cntrl);\ndrivers/accel/qaic/mhi_controller.c-930-\tif (ret)\ndrivers/accel/qaic/mhi_controller.c:931:\t\tpci_err(pci_dev, \"mhi_async_power_up failed after reset %d\\n\", ret);\ndrivers/accel/qaic/mhi_controller.c-932-}\n--\ndrivers/bus/mhi/host/init.c=193=static int mhi_init_irq_setup(struct mhi_controller *mhi_cntrl)\n--\ndrivers/bus/mhi/host/init.c-210-\t/*\ndrivers/bus/mhi/host/init.c:211:\t * IRQs should be enabled during mhi_async_power_up(), so disable them explicitly here.\ndrivers/bus/mhi/host/init.c-212-\t * Due to the use of IRQF_SHARED flag as default while requesting IRQs, we assume that\n--\ndrivers/bus/mhi/host/pci_generic.c=1363=static int mhi_pci_probe(struct pci_dev *pdev, const struct pci_device_id *id)\n--\ndrivers/bus/mhi/host/pci_generic.c-1448-\ndrivers/bus/mhi/host/pci_generic.c:1449:\terr = mhi_async_power_up(mhi_cntrl);\ndrivers/bus/mhi/host/pci_generic.c-1450-\tif (err) {\n--\ndrivers/bus/mhi/host/pm.c=1099=static void mhi_deassert_dev_wake(struct mhi_controller *mhi_cntrl,\n--\ndrivers/bus/mhi/host/pm.c-1120-\ndrivers/bus/mhi/host/pm.c:1121:int mhi_async_power_up(struct mhi_controller *mhi_cntrl)\ndrivers/bus/mhi/host/pm.c-1122-{\n--\ndrivers/bus/mhi/host/pm.c-1209-}\ndrivers/bus/mhi/host/pm.c:1210:EXPORT_SYMBOL_GPL(mhi_async_power_up);\ndrivers/bus/mhi/host/pm.c-1211-\n--\ndrivers/bus/mhi/host/pm.c=1277=int mhi_sync_power_up(struct mhi_controller *mhi_cntrl)\ndrivers/bus/mhi/host/pm.c-1278-{\ndrivers/bus/mhi/host/pm.c:1279:\tint ret = mhi_async_power_up(mhi_cntrl);\ndrivers/bus/mhi/host/pm.c-1280-\tu32 timeout_ms;\n--\ninclude/linux/mhi.h=620=int mhi_prepare_for_power_up(struct mhi_controller *mhi_cntrl);\n--\ninclude/linux/mhi.h-622-/**\ninclude/linux/mhi.h:623: * mhi_async_power_up - Start MHI power up sequence\ninclude/linux/mhi.h-624- * @mhi_cntrl: MHI controller\ninclude/linux/mhi.h-625- */\ninclude/linux/mhi.h:626:int mhi_async_power_up(struct mhi_controller *mhi_cntrl);\ninclude/linux/mhi.h-627-\n"
}

gemini-3.1-pro-preview

null

null

							input: 16381
							output: 42
							thoughts: 29
						

Okay, let's dive into this. Here's my take on what I'm about to do:

**Analyzing the Power-Up Sequence for the MHI Host Controller**

Alright, I'm going to take a look at the `mhi_async_power_up` function. The filename suggests we're dealing with asynchronous power-up procedures. I'll be checking `drivers/bus/mhi/host/pm.c` to see how the MHI host controller gets initialized and powered on within a power management context. I expect to see the typical pm_runtime_* calls or related mechanisms responsible for runtime power management. I'm keen to understand how this function handles potential race conditions, error conditions during the hardware initialization, and the role of this function in an overall power-up sequence from a low-power state. Specifically, I need to know how it interacts with the MHI bus and any dependent devices. I'll need to pay close attention to the use of any synchronization primitives like mutexes or spinlocks to ensure data integrity during the power transition. I also need to understand how it handles any device-specific quirks or workarounds in the initialization process. Let's see what we've got.

{
  "File": "drivers/bus/mhi/host/pm.c",
  "FirstLine": 1121,
  "LineCount": 100
}

{
  "Contents": "1121:\tint mhi_async_power_up(struct mhi_controller *mhi_cntrl)\n1122:\t{\n1123:\t\tstruct mhi_event *mhi_event = mhi_cntrl-\u003emhi_event;\n1124:\t\tenum mhi_state state;\n1125:\t\tenum mhi_ee_type current_ee;\n1126:\t\tenum dev_st_transition next_state;\n1127:\t\tstruct device *dev = \u0026mhi_cntrl-\u003emhi_dev-\u003edev;\n1128:\t\tu32 interval_us = 25000; /* poll register field every 25 milliseconds */\n1129:\t\tint ret, i;\n1130:\t\n1131:\t\tdev_info(dev, \"Requested to power ON\\n\");\n1132:\t\n1133:\t\t/* Supply default wake routines if not provided by controller driver */\n1134:\t\tif (!mhi_cntrl-\u003ewake_get || !mhi_cntrl-\u003ewake_put ||\n1135:\t\t    !mhi_cntrl-\u003ewake_toggle) {\n1136:\t\t\tmhi_cntrl-\u003ewake_get = mhi_assert_dev_wake;\n1137:\t\t\tmhi_cntrl-\u003ewake_put = mhi_deassert_dev_wake;\n1138:\t\t\tmhi_cntrl-\u003ewake_toggle = (mhi_cntrl-\u003edb_access \u0026 MHI_PM_M2) ?\n1139:\t\t\t\tmhi_toggle_dev_wake_nop : mhi_toggle_dev_wake;\n1140:\t\t}\n1141:\t\n1142:\t\tmutex_lock(\u0026mhi_cntrl-\u003epm_mutex);\n1143:\t\tmhi_cntrl-\u003epm_state = MHI_PM_DISABLE;\n1144:\t\n1145:\t\t/* Setup BHI INTVEC */\n1146:\t\twrite_lock_irq(\u0026mhi_cntrl-\u003epm_lock);\n1147:\t\tmhi_write_reg(mhi_cntrl, mhi_cntrl-\u003ebhi, BHI_INTVEC, 0);\n1148:\t\tmhi_cntrl-\u003epm_state = MHI_PM_POR;\n1149:\t\tmhi_cntrl-\u003eee = MHI_EE_MAX;\n1150:\t\tcurrent_ee = mhi_get_exec_env(mhi_cntrl);\n1151:\t\twrite_unlock_irq(\u0026mhi_cntrl-\u003epm_lock);\n1152:\t\n1153:\t\t/* Confirm that the device is in valid exec env */\n1154:\t\tif (!MHI_POWER_UP_CAPABLE(current_ee)) {\n1155:\t\t\tdev_err(dev, \"%s is not a valid EE for power on\\n\",\n1156:\t\t\t\tTO_MHI_EXEC_STR(current_ee));\n1157:\t\t\tret = -EIO;\n1158:\t\t\tgoto error_exit;\n1159:\t\t}\n1160:\t\n1161:\t\tstate = mhi_get_mhi_state(mhi_cntrl);\n1162:\t\tdev_dbg(dev, \"Attempting power on with EE: %s, state: %s\\n\",\n1163:\t\t\tTO_MHI_EXEC_STR(current_ee), mhi_state_str(state));\n1164:\t\n1165:\t\tif (state == MHI_STATE_SYS_ERR) {\n1166:\t\t\tmhi_set_mhi_state(mhi_cntrl, MHI_STATE_RESET);\n1167:\t\t\tret = mhi_poll_reg_field(mhi_cntrl, mhi_cntrl-\u003eregs, MHICTRL,\n1168:\t\t\t\t\t MHICTRL_RESET_MASK, 0, interval_us,\n1169:\t\t\t\t\t mhi_cntrl-\u003etimeout_ms);\n1170:\t\t\tif (ret) {\n1171:\t\t\t\tdev_info(dev, \"Failed to reset MHI due to syserr state\\n\");\n1172:\t\t\t\tgoto error_exit;\n1173:\t\t\t}\n1174:\t\n1175:\t\t\t/*\n1176:\t\t\t * device cleares INTVEC as part of RESET processing,\n1177:\t\t\t * re-program it\n1178:\t\t\t */\n1179:\t\t\tmhi_write_reg(mhi_cntrl, mhi_cntrl-\u003ebhi, BHI_INTVEC, 0);\n1180:\t\t}\n1181:\t\n1182:\t\t/* IRQs have been requested during probe, so we just need to enable them. */\n1183:\t\tenable_irq(mhi_cntrl-\u003eirq[0]);\n1184:\t\n1185:\t\tfor (i = 0; i \u003c mhi_cntrl-\u003etotal_ev_rings; i++, mhi_event++) {\n1186:\t\t\tif (mhi_event-\u003eoffload_ev)\n1187:\t\t\t\tcontinue;\n1188:\t\n1189:\t\t\tenable_irq(mhi_cntrl-\u003eirq[mhi_event-\u003eirq]);\n1190:\t\t}\n1191:\t\n1192:\t\t/* Transition to next state */\n1193:\t\tnext_state = MHI_IN_PBL(current_ee) ?\n1194:\t\t\tDEV_ST_TRANSITION_PBL : DEV_ST_TRANSITION_READY;\n1195:\t\n1196:\t\tmhi_queue_state_transition(mhi_cntrl, next_state);\n1197:\t\n1198:\t\tmutex_unlock(\u0026mhi_cntrl-\u003epm_mutex);\n1199:\t\n1200:\t\tdev_info(dev, \"Power on setup success\\n\");\n1201:\t\n1202:\t\treturn 0;\n1203:\t\n1204:\terror_exit:\n1205:\t\tmhi_cntrl-\u003epm_state = MHI_PM_DISABLE;\n1206:\t\tmutex_unlock(\u0026mhi_cntrl-\u003epm_mutex);\n1207:\t\n1208:\t\treturn ret;\n1209:\t}\n1210:\tEXPORT_SYMBOL_GPL(mhi_async_power_up);\n1211:\t\n1212:\tstatic void __mhi_power_down(struct mhi_controller *mhi_cntrl, bool graceful,\n1213:\t\t\t\t     bool destroy_device)\n1214:\t{\n1215:\t\tenum mhi_pm_state cur_state, transition_state;\n1216:\t\tstruct device *dev = \u0026mhi_cntrl-\u003emhi_dev-\u003edev;\n1217:\t\n1218:\t\tmutex_lock(\u0026mhi_cntrl-\u003epm_mutex);\n1219:\t\twrite_lock_irq(\u0026mhi_cntrl-\u003epm_lock);\n1220:\t\tcur_state = mhi_cntrl-\u003epm_state;\n"
}

gemini-3.1-pro-preview

null

null

							input: 18521
							output: 20
							thoughts: 249
						

**My Analysis of the MHI Async Power-Up Sequence**

Okay, let me break this down. My understanding is that `mhi_async_power_up` is the critical function here, and it's using the standard `mhi_write_reg` and `mhi_read_reg` for register access. Right, those are just wrappers that, in the `mhi_pci_generic.c` context, are ultimately calling `mhi_pci_read_reg` and `mhi_pci_write_reg`. Essentially, we're talking about direct memory access via `readl` and `writel` on the mapped PCI BAR.

Here's where it gets interesting, and potentially exploitable. Syzkaller's PCI fuzzer, which I know inside and out, can manipulate what's read from those BARs. It can return *anything* for a `readl` operation. So, if the fuzzer provides the "correct" values during `mhi_async_power_up`, it could trick the system into thinking everything's fine. For instance, if the fuzzer mimics the `MHI_POWER_UP_CAPABLE(current_ee)` condition, the function would seemingly succeed.

Hold on... this is all triggered by `mhi_pci_probe`, isn't it? If `mhi_async_power_up` manages to pass, then `mhi_pci_probe` completes successfully. Then what happens? Ah, then `mhi_queue_state_transition` is used to queue a work item. That's the key. That work item is going to eventually lead to the creation of MHI devices, including the channels, which is exactly where I'd focus my investigation. Time to dig into `mhi_create_devices` and see what it's expecting, and how it's using the data we were just looking at.

{
  "Expression": "mhi_create_devices"
}

{
  "Output": "drivers/bus/mhi/host/internal.h=321=int mhi_destroy_device(struct device *dev, void *data);\ndrivers/bus/mhi/host/internal.h:322:void mhi_create_devices(struct mhi_controller *mhi_cntrl);\ndrivers/bus/mhi/host/internal.h-323-\n--\ndrivers/bus/mhi/host/main.c=360=EXPORT_SYMBOL_GPL(mhi_notify);\n--\ndrivers/bus/mhi/host/main.c-362-/* Bind MHI channels to MHI devices */\ndrivers/bus/mhi/host/main.c:363:void mhi_create_devices(struct mhi_controller *mhi_cntrl)\ndrivers/bus/mhi/host/main.c-364-{\n--\ndrivers/bus/mhi/host/pm.c=394=static int mhi_pm_mission_mode_transition(struct mhi_controller *mhi_cntrl)\n--\ndrivers/bus/mhi/host/pm.c-459-\t */\ndrivers/bus/mhi/host/pm.c:460:\tmhi_create_devices(mhi_cntrl);\ndrivers/bus/mhi/host/pm.c-461-\n--\ndrivers/bus/mhi/host/pm.c=798=void mhi_pm_st_worker(struct work_struct *work)\n--\ndrivers/bus/mhi/host/pm.c-831-\t\t\t */\ndrivers/bus/mhi/host/pm.c:832:\t\t\tmhi_create_devices(mhi_cntrl);\ndrivers/bus/mhi/host/pm.c-833-\t\t\tif (mhi_cntrl-\u003efbc_download)\n--\ndrivers/bus/mhi/host/pm.c-844-\t\t\twrite_unlock_irq(\u0026mhi_cntrl-\u003epm_lock);\ndrivers/bus/mhi/host/pm.c:845:\t\t\tmhi_create_devices(mhi_cntrl);\ndrivers/bus/mhi/host/pm.c-846-\t\t\tmhi_uevent_notify(mhi_cntrl, mhi_cntrl-\u003eee);\n"
}

gemini-3.1-pro-preview

null

null

							input: 19780
							output: 22
							thoughts: 376
						

**My Analysis of the MHI WWAN Driver Patch**

Okay, let me break this down. From what I understand, `mhi_create_devices` gets triggered from either `mhi_pm_st_worker` or `mhi_pm_mission_mode_transition`. That's the entry point to create MHI devices, which then connect to their drivers, like `mhi_wwan_ctrl` and `mhi_wwan_dtr`. The patch is introducing `mhi_wwan_dtr_driver`, specifically for the "IP_CTRL" channel, and I see it's also modifying `mhi_wwan_ctrl_driver` to now send DTR/RTS messages using that same "IP_CTRL" channel.

The critical question, as always with these things, is if syzkaller can reach it. I think the answer is yes. Syzkaller's PCI emulation seems key here. It can emulate PCI devices, which would trigger `mhi_pci_probe`. And that, in turn, can start the chain: `mhi_async_power_up`, then `mhi_create_devices`, which eventually leads to the probing of `mhi_wwan_ctrl` and `mhi_wwan_dtr`. Once we've got those devices in place, syzkaller could then open the WWAN port and trigger `wwan_port_op_start`, which I believe, then calls the `dtr_rts` callback.

I need to confirm if `mhi_pci_generic` is reachable within the QEMU environment. It looks like syzkaller has a PCI fuzzer that injects PCI devices, so that seems promising. The key is that it doesn't *require* specific physical hardware, because that PCI fuzzer properly emulates PCI configuration space and the BARs.

One last check is to verify if `mhi_pci_generic` is actually enabled in the syzkaller configuration. Usually, `CONFIG_MHI_BUS` and `CONFIG_MHI_BUS_PCI_GENERIC` are either enabled by default or easily enabled. Now I should probably look at the Kconfig file for `mhi_wwan_ctrl` to confirm my assumptions.

{
  "Expression": "config MHI_WWAN_CTRL"
}

{
  "Output": "drivers/net/wwan/Kconfig=31=config WWAN_HWSIM\n--\ndrivers/net/wwan/Kconfig-39-\ndrivers/net/wwan/Kconfig:40:config MHI_WWAN_CTRL\ndrivers/net/wwan/Kconfig-41-\ttristate \"MHI WWAN control driver for Qualcomm-based PCIe modems\"\n"
}

gemini-3.1-pro-preview

null

null

							input: 20773
							output: 36
							thoughts: 25
						

Here's my thought process, as requested:

**Checking the Kconfig for MHI_WWAN_CTRL**

Okay, so I need to understand how `MHI_WWAN_CTRL` is configured within the kernel. My first instinct, given my experience, is to head directly to the Kconfig file for the WWAN drivers. Specifically, I'm thinking of `drivers/net/wwan/Kconfig`. That's where I expect to find the relevant configuration options and dependencies related to MHI (Mobile Host Interface) WWAN control. This is the logical starting point for investigating the control mechanism. Let's see what's in there. I'm anticipating finding the relevant `config` option definition, along with potential dependencies on other features or hardware configurations. I'm also hoping to see how the user can enable or disable this control flow.

{
  "File": "drivers/net/wwan/Kconfig",
  "FirstLine": 40,
  "LineCount": 20
}

{
  "Contents": "  40:\tconfig MHI_WWAN_CTRL\n  41:\t\ttristate \"MHI WWAN control driver for Qualcomm-based PCIe modems\"\n  42:\t\tdepends on MHI_BUS\n  43:\t\thelp\n  44:\t\t  MHI WWAN CTRL allows QCOM-based PCIe modems to expose different modem\n  45:\t\t  control protocols/ports to userspace, including AT, MBIM, QMI, DIAG\n  46:\t\t  and FIREHOSE. These protocols can be accessed directly from userspace\n  47:\t\t  (e.g. AT commands) or via libraries/tools (e.g. libmbim, libqmi,\n  48:\t\t  libqcdm...).\n  49:\t\n  50:\t\t  To compile this driver as a module, choose M here: the module will be\n  51:\t\t  called mhi_wwan_ctrl.\n  52:\t\n  53:\tconfig MHI_WWAN_MBIM\n  54:\t        tristate \"MHI WWAN MBIM network driver for Qualcomm-based PCIe modems\"\n  55:\t        depends on MHI_BUS\n  56:\t        help\n  57:\t          MHI WWAN MBIM is a WWAN network driver for QCOM-based PCIe modems.\n  58:\t          It implements MBIM over MHI, for IP data aggregation and muxing.\n  59:\t          A default wwan0 network interface is created for MBIM data session\n"
}

gemini-3.1-pro-preview

null

null

							input: 21387
							output: 24
							thoughts: 46
						

Here's my understanding of the situation, presented from my perspective as an embedded systems expert:

**Dependencies and Location**

Okay, so I'm looking at the dependencies here. It's clear that the `MHI_WWAN_CTRL` driver relies on `MHI_BUS`. That makes sense; the WWAN controller needs a bus to communicate over. Now, the next piece of the puzzle is the specific implementation of that `MHI_BUS`, namely `MHI_BUS_PCI_GENERIC`. Right, and where is that defined? Ah, I see, it's configured within the `drivers/bus/mhi/host/Kconfig` file. Perfect, this gives me a clear path to understand and potentially modify the MHI bus configuration if needed. It's good to know the dependency chain and where the relevant configuration options reside.

{
  "Expression": "config MHI_BUS_PCI_GENERIC"
}

{
  "Output": "drivers/bus/mhi/host/Kconfig=16=config MHI_BUS_DEBUG\n--\ndrivers/bus/mhi/host/Kconfig-23-\ndrivers/bus/mhi/host/Kconfig:24:config MHI_BUS_PCI_GENERIC\ndrivers/bus/mhi/host/Kconfig-25-\ttristate \"MHI PCI controller driver\"\n"
}

gemini-3.1-pro-preview

null

null

							input: 21745
							output: 38
							thoughts: 29
						

Okay, let's dive into this. I need to understand the configuration options for the MHI bus, specifically when it's using the PCI generic driver, so I'll be looking at the `drivers/bus/mhi/host/Kconfig` file. I'm going to focus on the section related to `MHI_BUS_PCI_GENERIC`, because that's the part I need to grok. My goal is to understand how this specific implementation is configured. This might involve looking at dependencies, default values, help text, and where this driver is supposed to fit into the broader system. I'm hoping to gain a solid understanding of its configurable aspects so I can troubleshoot the system properly.

{
  "File": "drivers/bus/mhi/host/Kconfig",
  "FirstLine": 24,
  "LineCount": 20
}

{
  "Contents": "  24:\tconfig MHI_BUS_PCI_GENERIC\n  25:\t\ttristate \"MHI PCI controller driver\"\n  26:\t\tdepends on MHI_BUS\n  27:\t\tdepends on PCI\n  28:\t\thelp\n  29:\t\t  This driver provides MHI PCI controller driver for devices such as\n  30:\t\t  Qualcomm SDX55 based PCIe modems.\n  31:\t\n"
}

gemini-3.1-pro-preview

null

null

							input: 22078
							output: 19
							thoughts: 225
						

**My Initial Assessment of the MHI Configuration**

Okay, so I see the dependencies: `CONFIG_MHI_BUS`, `CONFIG_MHI_BUS_PCI_GENERIC`, `CONFIG_WWAN`, and `CONFIG_MHI_WWAN_CTRL`. Seems straightforward enough, but hold on... the instructions are a bit more restrictive. They specifically mention drivers for PCIe switches, SmartNICs, or GPUs—things like `mlxsw`, `pds_core`, `qed`, `ionic`, and `amdgpu` – and the note highlights that these drivers *require* actual physical PCIe hardware, which isn't emulated in standard QEMU.

Now, the question is, does MHI, "Modem Host Interface" – specifically for Qualcomm modems over PCIe – fall into that category? Does it *absolutely* require physical hardware? My gut says it might, but I need to be sure. I'm thinking about Syzkaller's `syz_pci_device` which does a decent job emulating PCI devices. The big question is, can it realistically emulate the intricacies of the MHI protocol? We're talking about ring buffers, event rings, command rings, and the whole shebang. It's not a simple device.

Wait, is there even a syzkaller fuzzer specifically tailored for MHI? I should check. If there are existing syzkaller descriptions, that would provide a huge clue. Let me see what I can find. That should answer some of my questions.

no matches

{
  "Expression": "syz_mhi"
}

{
  "error": "no matches"
}

gemini-3.1-pro-preview

null

null

							input: 22660
							output: 40
							thoughts: 495
						

**My Line of Reasoning**

Okay, so I'm thinking about this `syz_mhi` situation. There's no obvious `syz_mhi` call in the code, but I'm wondering if syzkaller's PCI fuzzer could potentially get us past that initial `mhi_async_power_up` function. That function reads the execution environment (`EE`) via `mhi_get_exec_env(mhi_cntrl)`, which in turn reads the `BHI_EXECENV` register. If the PCI fuzzer can provide a valid EE, like `MHI_EE_AMSS`, then `MHI_POWER_UP_CAPABLE` becomes true, which is a good starting point.

From there, if the system is in an error state (`MHI_STATE_SYS_ERR`), it seems to poll `MHICTRL_RESET_MASK`. Then, it queues up `mhi_pm_st_worker`. The worker's going to call `mhi_pm_mission_mode_transition` or something similar, and that's the key: it will call `mhi_create_devices`.

Aha! `mhi_create_devices`... what does that do? It looks like it just creates devices based on the channel configuration provided by the PCI driver. Let me dig into `mhi_pci_generic.c` to see what channels are being created. Okay, here it is: there are channels like "MBIM", "QMI", and also "IP_CTRL". So `mhi_create_devices` will create an MHI device specifically named "IP_CTRL".

That's interesting because it means `mhi_wwan_dtr_probe` will be called, as it matches "IP_CTRL"! Wait a moment! `mhi_create_devices` calls `mhi_alloc_device` and then `device_add`. This looks like a promising path. But, the critical question: Does this whole thing, especially `mhi_create_devices`, require the MHI hardware to actually be doing anything meaningful? I need to go back and check the implementation of `mhi_create_devices` carefully to be sure.

{
  "File": "drivers/bus/mhi/host/main.c",
  "FirstLine": 363,
  "LineCount": 50
}

{
  "Contents": " 363:\tvoid mhi_create_devices(struct mhi_controller *mhi_cntrl)\n 364:\t{\n 365:\t\tstruct mhi_chan *mhi_chan;\n 366:\t\tstruct mhi_device *mhi_dev;\n 367:\t\tstruct device *dev = \u0026mhi_cntrl-\u003emhi_dev-\u003edev;\n 368:\t\tint i, ret;\n 369:\t\n 370:\t\tmhi_chan = mhi_cntrl-\u003emhi_chan;\n 371:\t\tfor (i = 0; i \u003c mhi_cntrl-\u003emax_chan; i++, mhi_chan++) {\n 372:\t\t\tif (!mhi_chan-\u003econfigured || mhi_chan-\u003emhi_dev ||\n 373:\t\t\t    !(mhi_chan-\u003eee_mask \u0026 BIT(mhi_cntrl-\u003eee)))\n 374:\t\t\t\tcontinue;\n 375:\t\t\tmhi_dev = mhi_alloc_device(mhi_cntrl);\n 376:\t\t\tif (IS_ERR(mhi_dev))\n 377:\t\t\t\treturn;\n 378:\t\n 379:\t\t\tmhi_dev-\u003edev_type = MHI_DEVICE_XFER;\n 380:\t\t\tswitch (mhi_chan-\u003edir) {\n 381:\t\t\tcase DMA_TO_DEVICE:\n 382:\t\t\t\tmhi_dev-\u003eul_chan = mhi_chan;\n 383:\t\t\t\tmhi_dev-\u003eul_chan_id = mhi_chan-\u003echan;\n 384:\t\t\t\tbreak;\n 385:\t\t\tcase DMA_FROM_DEVICE:\n 386:\t\t\t\t/* We use dl_chan as offload channels */\n 387:\t\t\t\tmhi_dev-\u003edl_chan = mhi_chan;\n 388:\t\t\t\tmhi_dev-\u003edl_chan_id = mhi_chan-\u003echan;\n 389:\t\t\t\tbreak;\n 390:\t\t\tdefault:\n 391:\t\t\t\tdev_err(dev, \"Direction not supported\\n\");\n 392:\t\t\t\tput_device(\u0026mhi_dev-\u003edev);\n 393:\t\t\t\treturn;\n 394:\t\t\t}\n 395:\t\n 396:\t\t\tget_device(\u0026mhi_dev-\u003edev);\n 397:\t\t\tmhi_chan-\u003emhi_dev = mhi_dev;\n 398:\t\n 399:\t\t\t/* Check next channel if it matches */\n 400:\t\t\tif ((i + 1) \u003c mhi_cntrl-\u003emax_chan \u0026\u0026 mhi_chan[1].configured) {\n 401:\t\t\t\tif (!strcmp(mhi_chan[1].name, mhi_chan-\u003ename)) {\n 402:\t\t\t\t\ti++;\n 403:\t\t\t\t\tmhi_chan++;\n 404:\t\t\t\t\tif (mhi_chan-\u003edir == DMA_TO_DEVICE) {\n 405:\t\t\t\t\t\tmhi_dev-\u003eul_chan = mhi_chan;\n 406:\t\t\t\t\t\tmhi_dev-\u003eul_chan_id = mhi_chan-\u003echan;\n 407:\t\t\t\t\t} else {\n 408:\t\t\t\t\t\tmhi_dev-\u003edl_chan = mhi_chan;\n 409:\t\t\t\t\t\tmhi_dev-\u003edl_chan_id = mhi_chan-\u003echan;\n 410:\t\t\t\t\t}\n 411:\t\t\t\t\tget_device(\u0026mhi_dev-\u003edev);\n 412:\t\t\t\t\tmhi_chan-\u003emhi_dev = mhi_dev;\n"
}

gemini-3.1-pro-preview

null

null

							input: 24570
							output: 23
							thoughts: 164
						

**My Analysis of Device Creation in the MHI Driver**

Okay, so `mhi_create_devices` really just boils down to creating devices according to a static configuration array. That's straightforward enough. The core logic hinges on this `mhi_chan->ee_mask & BIT(mhi_cntrl->ee)` check. Essentially, if the PCI fuzzer, which is providing the execution environment, spits out an `ee` that aligns with the channel's `ee_mask`, then a device gets instantiated.

Now, here's where it gets interesting. I'm looking at the channel configuration for "IP_CTRL" in `mhi_sierra_em919x_channels`. The `ee_mask` is set to 0. Hmm, that feels a bit... permissive. I need to be sure. I'm recalling the macro: `MHI_CHANNEL_CONFIG_UL(18, "IP_CTRL", 32, 0)`. Yup, that last argument is definitely a `0`, which is the `ee_mask`. So any `ee` returned that has a bit set matching `0`, and a device will be created. I'm going to have to check the definition of that macro to understand how it's working; it seems like I am missing a detail.

{
  "Expression": "define MHI_CHANNEL_CONFIG_UL"
}

{
  "Output": "drivers/bus/mhi/host/pci_generic.c=51=struct mhi_pci_dev_info {\n--\ndrivers/bus/mhi/host/pci_generic.c-66-\ndrivers/bus/mhi/host/pci_generic.c:67:#define MHI_CHANNEL_CONFIG_UL(ch_num, ch_name, el_count, ev_ring) \\\ndrivers/bus/mhi/host/pci_generic.c-68-\t{\t\t\t\t\t\t\\\n--\ndrivers/bus/mhi/host/pci_generic.c-139-\ndrivers/bus/mhi/host/pci_generic.c:140:#define MHI_CHANNEL_CONFIG_UL_SBL(ch_num, ch_name, el_count, ev_ring) \\\ndrivers/bus/mhi/host/pci_generic.c-141-\t{\t\t\t\t\t\t\\\n--\ndrivers/bus/mhi/host/pci_generic.c-169-\ndrivers/bus/mhi/host/pci_generic.c:170:#define MHI_CHANNEL_CONFIG_UL_FP(ch_num, ch_name, el_count, ev_ring) \\\ndrivers/bus/mhi/host/pci_generic.c-171-\t{\t\t\t\t\t\t\\\n"
}

gemini-3.1-pro-preview

null

null

							input: 25375
							output: 42
							thoughts: 16
						

Okay, let's dive into this. Here's my take on those thoughts, as if they're my own:

**Analyzing the `MHI_CHANNEL_CONFIG_UL` Definition**

Alright, time to get to the core of this. I need to understand what's going on with this `MHI_CHANNEL_CONFIG_UL` definition. I know MHI (Mobile Host Interface) intimately, so this likely relates to the upstream channel configuration, but the specifics are where the devil is. My expertise tells me that this definition probably outlines the parameters that control the behavior of the upstream link. I'm thinking: is it related to buffer sizes, transfer rates, error correction, flow control, or some other critical aspect? Knowing the specifics of the `UL` part clarifies it's specifically about the "upstream link" or the "uplink." Time to start picking apart this definition and see exactly what bits and pieces it reveals. I'm expecting this to relate to a data transfer path, and the definition holds the keys to understanding what's allowed. Let's see... let's see what we've got.

{
  "File": "drivers/bus/mhi/host/pci_generic.c",
  "FirstLine": 67,
  "LineCount": 20
}

{
  "Contents": "  67:\t#define MHI_CHANNEL_CONFIG_UL(ch_num, ch_name, el_count, ev_ring) \\\n  68:\t\t{\t\t\t\t\t\t\\\n  69:\t\t\t.num = ch_num,\t\t\t\t\\\n  70:\t\t\t.name = ch_name,\t\t\t\\\n  71:\t\t\t.num_elements = el_count,\t\t\\\n  72:\t\t\t.event_ring = ev_ring,\t\t\t\\\n  73:\t\t\t.dir = DMA_TO_DEVICE,\t\t\t\\\n  74:\t\t\t.ee_mask = BIT(MHI_EE_AMSS),\t\t\\\n  75:\t\t\t.pollcfg = 0,\t\t\t\t\\\n  76:\t\t\t.doorbell = MHI_DB_BRST_DISABLE,\t\\\n  77:\t\t\t.lpm_notify = false,\t\t\t\\\n  78:\t\t\t.offload_channel = false,\t\t\\\n  79:\t\t\t.doorbell_mode_switch = false,\t\t\\\n  80:\t\t}\t\t\t\t\t\t\\\n  81:\t\n  82:\t#define MHI_CHANNEL_CONFIG_DL(ch_num, ch_name, el_count, ev_ring) \\\n  83:\t\t{\t\t\t\t\t\t\\\n  84:\t\t\t.num = ch_num,\t\t\t\t\\\n  85:\t\t\t.name = ch_name,\t\t\t\\\n  86:\t\t\t.num_elements = el_count,\t\t\\\n"
}

gemini-3.1-pro-preview

null

null

							input: 26024
							output: 40
							thoughts: 244
						

**My Analysis of the MHI Channel Creation Logic**

Okay, so here's what I've got so far. The key seems to be `ee_mask`, which, in this case, is defined as `BIT(MHI_EE_AMSS)`. My understanding is, if the fuzzer can set `mhi_cntrl->ee` to `MHI_EE_AMSS`, we'll get that channel created. That's the target.

I see that `mhi_cntrl->ee` is initialized within `mhi_async_power_up`, where it's initially set to `MHI_EE_MAX`. And then, this `current_ee` variable is populated by calling `mhi_get_exec_env`. This `mhi_get_exec_env` is clearly critical - it's reading the value from `BHI_EXECENV`. So, if the fuzzer, through influencing `BHI_EXECENV`, can make `mhi_get_exec_env` return `MHI_EE_AMSS`, then `current_ee` will be set to `MHI_EE_AMSS`.

However, wait a second. I just realized there's a subsequent update to `mhi_cntrl->ee` within `mhi_pm_mission_mode_transition`. It looks like it forces `mhi_cntrl->ee` to `MHI_EE_AMSS` directly.

So, I need to understand that. I need to check how `mhi_pm_mission_mode_transition` works. That's the key.

{
  "File": "drivers/bus/mhi/host/pm.c",
  "FirstLine": 394,
  "LineCount": 50
}

{
  "Contents": " 394:\tstatic int mhi_pm_mission_mode_transition(struct mhi_controller *mhi_cntrl)\n 395:\t{\n 396:\t\tstruct mhi_event *mhi_event;\n 397:\t\tstruct device *dev = \u0026mhi_cntrl-\u003emhi_dev-\u003edev;\n 398:\t\tenum mhi_ee_type ee = MHI_EE_MAX, current_ee = mhi_cntrl-\u003eee;\n 399:\t\tint i, ret;\n 400:\t\n 401:\t\tdev_dbg(dev, \"Processing Mission Mode transition\\n\");\n 402:\t\n 403:\t\twrite_lock_irq(\u0026mhi_cntrl-\u003epm_lock);\n 404:\t\tif (MHI_REG_ACCESS_VALID(mhi_cntrl-\u003epm_state))\n 405:\t\t\tee = mhi_get_exec_env(mhi_cntrl);\n 406:\t\n 407:\t\tif (!MHI_IN_MISSION_MODE(ee)) {\n 408:\t\t\tmhi_cntrl-\u003epm_state = MHI_PM_LD_ERR_FATAL_DETECT;\n 409:\t\t\twrite_unlock_irq(\u0026mhi_cntrl-\u003epm_lock);\n 410:\t\t\twake_up_all(\u0026mhi_cntrl-\u003estate_event);\n 411:\t\t\treturn -EIO;\n 412:\t\t}\n 413:\t\tmhi_cntrl-\u003eee = ee;\n 414:\t\twrite_unlock_irq(\u0026mhi_cntrl-\u003epm_lock);\n 415:\t\n 416:\t\twake_up_all(\u0026mhi_cntrl-\u003estate_event);\n 417:\t\n 418:\t\tdevice_for_each_child(\u0026mhi_cntrl-\u003emhi_dev-\u003edev, \u0026current_ee,\n 419:\t\t\t\t      mhi_destroy_device);\n 420:\t\tmhi_cntrl-\u003estatus_cb(mhi_cntrl, MHI_CB_EE_MISSION_MODE);\n 421:\t\tmhi_uevent_notify(mhi_cntrl, mhi_cntrl-\u003eee);\n 422:\t\n 423:\t\t/* Force MHI to be in M0 state before continuing */\n 424:\t\tret = __mhi_device_get_sync(mhi_cntrl);\n 425:\t\tif (ret)\n 426:\t\t\treturn ret;\n 427:\t\n 428:\t\tread_lock_bh(\u0026mhi_cntrl-\u003epm_lock);\n 429:\t\n 430:\t\tif (MHI_PM_IN_ERROR_STATE(mhi_cntrl-\u003epm_state)) {\n 431:\t\t\tret = -EIO;\n 432:\t\t\tgoto error_mission_mode;\n 433:\t\t}\n 434:\t\n 435:\t\t/* Add elements to all HW event rings */\n 436:\t\tmhi_event = mhi_cntrl-\u003emhi_event;\n 437:\t\tfor (i = 0; i \u003c mhi_cntrl-\u003etotal_ev_rings; i++, mhi_event++) {\n 438:\t\t\tstruct mhi_ring *ring = \u0026mhi_event-\u003ering;\n 439:\t\n 440:\t\t\tif (mhi_event-\u003eoffload_ev || !mhi_event-\u003ehw_ring)\n 441:\t\t\t\tcontinue;\n 442:\t\n 443:\t\t\tring-\u003ewp = ring-\u003ebase + ring-\u003elen - ring-\u003eel_size;\n"
}

gemini-3.1-pro-preview

null

null

							input: 27589
							output: 40
							thoughts: 1292
						

**Fuzzing the MHI Driver: A Promising Path**

Okay, here's the breakdown of what I'm thinking. If the fuzzer can force `mhi_get_exec_env` to return `MHI_EE_AMSS`, then the `mhi_cntrl->ee` will become `MHI_EE_AMSS`, which triggers the creation of the "IP_CTRL" device through `mhi_create_devices`. After that, `mhi_wwan_dtr_probe` gets called, which triggers other probes like `mhi_wwan_ctrl_probe` for various channels. Critically, `mhi_wwan_ctrl_probe` will create a WWAN port. I see it right here: `port = wwan_create_port(...)`.

Then, if syzkaller can open a device like `/dev/wwan0at0`, the `wwan_port_op_start` operation gets called. This seems pretty straightforward. The critical part is here: when the port opens, if it's the first time and an AT port, the DTR/RTS bits are raised. This, in turn, calls `mhi_wwan_ctrl_dtr_rts`.

And here's where it gets interesting: `mhi_wwan_ctrl_dtr_rts` eventually calls `mhi_wwan_ctrl_send_dtr`. This function looks like the target, with all the pieces in place: `mhi_wwan_dev`, `mhi_controller`, `mhi_device`, and a call to `mhi_queue_buf` which I know can be a good fuzz target. It appears to send a buffer over the MHI bus!

So, the PCI fuzzer, running syzkaller, can emulate the MHI controller. It can trigger device creation. And then the WWAN fuzzer can open the port and then, finally, trigger `mhi_wwan_ctrl_send_dtr` and all the related calls.

Now, the question of physical hardware comes up, but the MHI driver *is* a PCI driver, and syzkaller's `syz_pci_device` can emulate the PCI device. So, the PCI fuzzer should be able to trigger this entire flow. This is where I have to be careful. The PCI fuzzer can return arbitrary values for BAR reads. The question is, can we *force* the fuzzer to return `MHI_EE_AMSS`, which is `0x2`?

I have to think about the probability here. Is `2` returned often enough to trigger this? Also, this is a virtualized environment, and it is possible to reach it. There is no physical PCIe hardware requirement. However, I have to consider the instructions. "Code in vendor-specific PCIe switch, SmartNIC, or GPU drivers (e.g., mlxsw, pds_core, qed, ionic, amdgpu) that require physical PCIe hardware cards not emulated in standard QEMU."

Is MHI one of those? Is it emulated in standard QEMU? No, QEMU does not have an MHI emulator, it can only be emulated via syzkaller's PCI fuzzer. MHI is the Qualcomm Modem Host Interface, and it is a bus. `mhi_pci_generic` is the PCI driver for the bus. Therefore, Syzkaller's PCI fuzzer can bind to it.

The MHI is quite complex and has rings, contexts, etc. Now, can syzkaller's PCI fuzzer actually get past `mhi_async_power_up`? I need to check `mhi_async_power_up` again. I have to make sure it is possible to trigger the code, especially that it polls the `MHICTRL_RESET_MASK` and queues `mhi_pm_st_worker`, which then waits for some callback that I have to check.

{
  "File": "drivers/bus/mhi/host/pm.c",
  "FirstLine": 798,
  "LineCount": 50
}

{
  "Contents": " 798:\tvoid mhi_pm_st_worker(struct work_struct *work)\n 799:\t{\n 800:\t\tstruct state_transition *itr, *tmp;\n 801:\t\tLIST_HEAD(head);\n 802:\t\tstruct mhi_controller *mhi_cntrl = container_of(work,\n 803:\t\t\t\t\t\t\t\tstruct mhi_controller,\n 804:\t\t\t\t\t\t\t\tst_worker);\n 805:\t\n 806:\t\tspin_lock_irq(\u0026mhi_cntrl-\u003etransition_lock);\n 807:\t\tlist_splice_tail_init(\u0026mhi_cntrl-\u003etransition_list, \u0026head);\n 808:\t\tspin_unlock_irq(\u0026mhi_cntrl-\u003etransition_lock);\n 809:\t\n 810:\t\tlist_for_each_entry_safe(itr, tmp, \u0026head, node) {\n 811:\t\t\tlist_del(\u0026itr-\u003enode);\n 812:\t\n 813:\t\t\ttrace_mhi_pm_st_transition(mhi_cntrl, itr-\u003estate);\n 814:\t\n 815:\t\t\tswitch (itr-\u003estate) {\n 816:\t\t\tcase DEV_ST_TRANSITION_PBL:\n 817:\t\t\t\twrite_lock_irq(\u0026mhi_cntrl-\u003epm_lock);\n 818:\t\t\t\tif (MHI_REG_ACCESS_VALID(mhi_cntrl-\u003epm_state))\n 819:\t\t\t\t\tmhi_cntrl-\u003eee = mhi_get_exec_env(mhi_cntrl);\n 820:\t\t\t\twrite_unlock_irq(\u0026mhi_cntrl-\u003epm_lock);\n 821:\t\t\t\tmhi_fw_load_handler(mhi_cntrl);\n 822:\t\t\t\tbreak;\n 823:\t\t\tcase DEV_ST_TRANSITION_SBL:\n 824:\t\t\t\twrite_lock_irq(\u0026mhi_cntrl-\u003epm_lock);\n 825:\t\t\t\tmhi_cntrl-\u003eee = MHI_EE_SBL;\n 826:\t\t\t\twrite_unlock_irq(\u0026mhi_cntrl-\u003epm_lock);\n 827:\t\t\t\t/*\n 828:\t\t\t\t * The MHI devices are only created when the client\n 829:\t\t\t\t * device switches its Execution Environment (EE) to\n 830:\t\t\t\t * either SBL or AMSS states\n 831:\t\t\t\t */\n 832:\t\t\t\tmhi_create_devices(mhi_cntrl);\n 833:\t\t\t\tif (mhi_cntrl-\u003efbc_download)\n 834:\t\t\t\t\tmhi_download_amss_image(mhi_cntrl);\n 835:\t\n 836:\t\t\t\tmhi_uevent_notify(mhi_cntrl, mhi_cntrl-\u003eee);\n 837:\t\t\t\tbreak;\n 838:\t\t\tcase DEV_ST_TRANSITION_MISSION_MODE:\n 839:\t\t\t\tmhi_pm_mission_mode_transition(mhi_cntrl);\n 840:\t\t\t\tbreak;\n 841:\t\t\tcase DEV_ST_TRANSITION_FP:\n 842:\t\t\t\twrite_lock_irq(\u0026mhi_cntrl-\u003epm_lock);\n 843:\t\t\t\tmhi_cntrl-\u003eee = MHI_EE_FP;\n 844:\t\t\t\twrite_unlock_irq(\u0026mhi_cntrl-\u003epm_lock);\n 845:\t\t\t\tmhi_create_devices(mhi_cntrl);\n 846:\t\t\t\tmhi_uevent_notify(mhi_cntrl, mhi_cntrl-\u003eee);\n 847:\t\t\t\tbreak;\n"
}

gemini-3.1-pro-preview

null

null

							input: 30720
							output: 40
							thoughts: 165
						

**My Analysis of the MHI Async Power-Up Sequence**

Okay, so looking at this `mhi_async_power_up` function, I see it's responsible for queuing either `DEV_ST_TRANSITION_READY` or `DEV_ST_TRANSITION_PBL`. That makes sense; it's the core of the power-up transition. Now, the crucial part is determining which state it's going to queue. It looks like the decision hinges on this `MHI_IN_PBL(current_ee)` check within `mhi_async_power_up`.

Let's break that down: the code snippet shows us that the `next_state` is set based on this: if the `current_ee` is in PBL, the transition to `DEV_ST_TRANSITION_PBL` occurs, otherwise `DEV_ST_TRANSITION_READY`.  So, if `current_ee` is `MHI_EE_AMSS`, then `MHI_IN_PBL` will be false, thus, `DEV_ST_TRANSITION_READY` will be queued. This is the path I want to trace. Now I need to understand what actually happens when we hit `DEV_ST_TRANSITION_READY` within the `mhi_pm_st_worker` function. That's the next critical step to analyze.

{
  "File": "drivers/bus/mhi/host/pm.c",
  "FirstLine": 848,
  "LineCount": 50
}

{
  "Contents": " 848:\t\t\tcase DEV_ST_TRANSITION_READY:\n 849:\t\t\t\tmhi_ready_state_transition(mhi_cntrl);\n 850:\t\t\t\tbreak;\n 851:\t\t\tcase DEV_ST_TRANSITION_SYS_ERR:\n 852:\t\t\t\tmhi_pm_sys_error_transition(mhi_cntrl);\n 853:\t\t\t\tbreak;\n 854:\t\t\tcase DEV_ST_TRANSITION_DISABLE:\n 855:\t\t\t\tmhi_pm_disable_transition(mhi_cntrl, false);\n 856:\t\t\t\tbreak;\n 857:\t\t\tcase DEV_ST_TRANSITION_DISABLE_DESTROY_DEVICE:\n 858:\t\t\t\tmhi_pm_disable_transition(mhi_cntrl, true);\n 859:\t\t\t\tbreak;\n 860:\t\t\tdefault:\n 861:\t\t\t\tbreak;\n 862:\t\t\t}\n 863:\t\t\tkfree(itr);\n 864:\t\t}\n 865:\t}\n 866:\t\n 867:\tint mhi_pm_suspend(struct mhi_controller *mhi_cntrl)\n 868:\t{\n 869:\t\tstruct mhi_chan *itr, *tmp;\n 870:\t\tstruct device *dev = \u0026mhi_cntrl-\u003emhi_dev-\u003edev;\n 871:\t\tenum mhi_pm_state new_state;\n 872:\t\tint ret;\n 873:\t\n 874:\t\tif (mhi_cntrl-\u003epm_state == MHI_PM_DISABLE)\n 875:\t\t\treturn -EINVAL;\n 876:\t\n 877:\t\tif (MHI_PM_IN_ERROR_STATE(mhi_cntrl-\u003epm_state))\n 878:\t\t\treturn -EIO;\n 879:\t\n 880:\t\t/* Return busy if there are any pending resources */\n 881:\t\tif (atomic_read(\u0026mhi_cntrl-\u003edev_wake) ||\n 882:\t\t    atomic_read(\u0026mhi_cntrl-\u003epending_pkts))\n 883:\t\t\treturn -EBUSY;\n 884:\t\n 885:\t\t/* Take MHI out of M2 state */\n 886:\t\tread_lock_bh(\u0026mhi_cntrl-\u003epm_lock);\n 887:\t\tmhi_cntrl-\u003ewake_get(mhi_cntrl, false);\n 888:\t\tread_unlock_bh(\u0026mhi_cntrl-\u003epm_lock);\n 889:\t\n 890:\t\tret = wait_event_timeout(mhi_cntrl-\u003estate_event,\n 891:\t\t\t\t\t mhi_cntrl-\u003edev_state == MHI_STATE_M0 ||\n 892:\t\t\t\t\t mhi_cntrl-\u003edev_state == MHI_STATE_M1 ||\n 893:\t\t\t\t\t MHI_PM_IN_ERROR_STATE(mhi_cntrl-\u003epm_state),\n 894:\t\t\t\t\t msecs_to_jiffies(mhi_cntrl-\u003etimeout_ms));\n 895:\t\n 896:\t\tread_lock_bh(\u0026mhi_cntrl-\u003epm_lock);\n 897:\t\tmhi_cntrl-\u003ewake_put(mhi_cntrl, false);\n"
}

gemini-3.1-pro-preview

null

null

							input: 32071
							output: 22
							thoughts: 14
						

Okay, let's dive into this. Here's how I'd approach summarizing the prompt, as if it were my own thought process:

**Focusing on `mhi_ready_state_transition`**

Alright, the directive is clear – let's shift our focus to investigating the `mhi_ready_state_transition` function or process. I need to understand its behavior and implications within the broader system. I'm immediately thinking about what context I need to consider; is this related to hardware initialization, inter-process communication, or a specific state management mechanism? My expert intuition suggests I'll need to look at the surrounding code to determine inputs, outputs, and any conditional logic associated with this specific transition. I'll be looking for potential issues related to concurrency, error handling, or unexpected side effects. Knowing how it interacts with other system components is essential for a thorough understanding.

{
  "Expression": "mhi_ready_state_transition"
}

{
  "Output": "drivers/bus/mhi/host/boot.c=474=void mhi_fw_load_handler(struct mhi_controller *mhi_cntrl)\n--\ndrivers/bus/mhi/host/boot.c-593-\t/* Transitioning into MHI RESET-\u003eREADY state */\ndrivers/bus/mhi/host/boot.c:594:\tret = mhi_ready_state_transition(mhi_cntrl);\ndrivers/bus/mhi/host/boot.c-595-\tif (ret) {\n--\ndrivers/bus/mhi/host/internal.h=337=void mhi_pm_sys_err_handler(struct mhi_controller *mhi_cntrl);\ndrivers/bus/mhi/host/internal.h:338:int mhi_ready_state_transition(struct mhi_controller *mhi_cntrl);\ndrivers/bus/mhi/host/internal.h-339-int mhi_pm_m0_transition(struct mhi_controller *mhi_cntrl);\n--\ndrivers/bus/mhi/host/pm.c=163=static void mhi_toggle_dev_wake(struct mhi_controller *mhi_cntrl)\n--\ndrivers/bus/mhi/host/pm.c-169-/* Handle device ready state transition */\ndrivers/bus/mhi/host/pm.c:170:int mhi_ready_state_transition(struct mhi_controller *mhi_cntrl)\ndrivers/bus/mhi/host/pm.c-171-{\n--\ndrivers/bus/mhi/host/pm.c=798=void mhi_pm_st_worker(struct work_struct *work)\n--\ndrivers/bus/mhi/host/pm.c-848-\t\tcase DEV_ST_TRANSITION_READY:\ndrivers/bus/mhi/host/pm.c:849:\t\t\tmhi_ready_state_transition(mhi_cntrl);\ndrivers/bus/mhi/host/pm.c-850-\t\t\tbreak;\n"
}

gemini-3.1-pro-preview

null

null

							input: 32815
							output: 40
							thoughts: 14
						

Okay, here's my interpretation of that thought process, assuming I'm deeply familiar with this kind of system:

**Analyzing `mhi_ready_state_transition`**

Alright, let's dive in. Reading `mhi_ready_state_transition` immediately signals a specific area of interest. This function, or module, is central to managing the ready state transitions within the MHI (presumably some kind of multi-host interface) system. I need to understand how things are moving between states; what triggers these changes, and what consequences follow each transition. This is crucial for debugging, performance optimization, and generally grasping the operational flow of the system. I anticipate that this will involve checking state machine logic, interrupt handling (if applicable), error conditions, and the data dependencies involved in switching states. I'm mentally preparing to scrutinize any potential race conditions or atomicity issues, particularly if this is dealing with shared resources or concurrent operations. Let's get to it!

{
  "File": "drivers/bus/mhi/host/pm.c",
  "FirstLine": 170,
  "LineCount": 50
}

{
  "Contents": " 170:\tint mhi_ready_state_transition(struct mhi_controller *mhi_cntrl)\n 171:\t{\n 172:\t\tstruct mhi_event *mhi_event;\n 173:\t\tenum mhi_pm_state cur_state;\n 174:\t\tstruct device *dev = \u0026mhi_cntrl-\u003emhi_dev-\u003edev;\n 175:\t\tu32 interval_us = 25000; /* poll register field every 25 milliseconds */\n 176:\t\tu32 timeout_ms;\n 177:\t\tint ret, i;\n 178:\t\n 179:\t\t/* Check if device entered error state */\n 180:\t\tif (MHI_PM_IN_FATAL_STATE(mhi_cntrl-\u003epm_state)) {\n 181:\t\t\tdev_err(dev, \"Device link is not accessible\\n\");\n 182:\t\t\treturn -EIO;\n 183:\t\t}\n 184:\t\n 185:\t\t/* Wait for RESET to be cleared and READY bit to be set by the device */\n 186:\t\tret = mhi_poll_reg_field(mhi_cntrl, mhi_cntrl-\u003eregs, MHICTRL,\n 187:\t\t\t\t\t MHICTRL_RESET_MASK, 0, interval_us,\n 188:\t\t\t\t\t mhi_cntrl-\u003etimeout_ms);\n 189:\t\tif (ret) {\n 190:\t\t\tdev_err(dev, \"Device failed to clear MHI Reset\\n\");\n 191:\t\t\treturn ret;\n 192:\t\t}\n 193:\t\n 194:\t\ttimeout_ms = mhi_cntrl-\u003eready_timeout_ms ?\n 195:\t\t\tmhi_cntrl-\u003eready_timeout_ms : mhi_cntrl-\u003etimeout_ms;\n 196:\t\tret = mhi_poll_reg_field(mhi_cntrl, mhi_cntrl-\u003eregs, MHISTATUS,\n 197:\t\t\t\t\t MHISTATUS_READY_MASK, 1, interval_us,\n 198:\t\t\t\t\t timeout_ms);\n 199:\t\tif (ret) {\n 200:\t\t\tdev_err(dev, \"Device failed to enter MHI Ready\\n\");\n 201:\t\t\treturn ret;\n 202:\t\t}\n 203:\t\n 204:\t\tdev_dbg(dev, \"Device in READY State\\n\");\n 205:\t\twrite_lock_irq(\u0026mhi_cntrl-\u003epm_lock);\n 206:\t\tcur_state = mhi_tryset_pm_state(mhi_cntrl, MHI_PM_POR);\n 207:\t\tmhi_cntrl-\u003edev_state = MHI_STATE_READY;\n 208:\t\twrite_unlock_irq(\u0026mhi_cntrl-\u003epm_lock);\n 209:\t\n 210:\t\tif (cur_state != MHI_PM_POR) {\n 211:\t\t\tdev_err(dev, \"Error moving to state %s from %s\\n\",\n 212:\t\t\t\tto_mhi_pm_state_str(MHI_PM_POR),\n 213:\t\t\t\tto_mhi_pm_state_str(cur_state));\n 214:\t\t\treturn -EIO;\n 215:\t\t}\n 216:\t\n 217:\t\tread_lock_bh(\u0026mhi_cntrl-\u003epm_lock);\n 218:\t\tif (!MHI_REG_ACCESS_VALID(mhi_cntrl-\u003epm_state)) {\n 219:\t\t\tdev_err(dev, \"Device registers not accessible\\n\");\n"
}

gemini-3.1-pro-preview

null

null

							input: 34015
							output: 40
							thoughts: 118
						

**My Analysis of the MHI State Transition**

Okay, so I'm looking at this code and breaking down what it's doing with the MHI (presumably a Mobile Host Interface). I see that it's checking specific bits within the `MHICTRL` and `MHISTATUS` registers.  Specifically, it's polling to make sure `MHICTRL_RESET_MASK` is set to 0, which I interpret as the system *not* being in a reset state, and that `MHISTATUS_READY_MASK` is 1, which likely indicates the device is ready.  

A successful fuzz test here means the fuzzer is returning those specific values – 0 for `MHICTRL` (meaning no reset) and 1 for `MHISTATUS_READY_MASK`.  Since `MHISTATUS_READY_MASK` is defined as `BIT(0)`, that bit being set to one means the low bit is active. If those checks pass, the code proceeds to set `mhi_cntrl->dev_state = MHI_STATE_READY`. This is the critical hand-off point. It means the MHI is now declared ready for operation.

The interesting stuff begins after that.  I need to understand the rest of the `mhi_ready_state_transition` function. I will go on and examine the subsequent code to understand exactly what other actions are triggered.

{
  "File": "drivers/bus/mhi/host/pm.c",
  "FirstLine": 220,
  "LineCount": 50
}

{
  "Contents": " 220:\t\t\tgoto error_mmio;\n 221:\t\t}\n 222:\t\n 223:\t\t/* Configure MMIO registers */\n 224:\t\tret = mhi_init_mmio(mhi_cntrl);\n 225:\t\tif (ret) {\n 226:\t\t\tdev_err(dev, \"Error configuring MMIO registers\\n\");\n 227:\t\t\tgoto error_mmio;\n 228:\t\t}\n 229:\t\n 230:\t\t/* Add elements to all SW event rings */\n 231:\t\tmhi_event = mhi_cntrl-\u003emhi_event;\n 232:\t\tfor (i = 0; i \u003c mhi_cntrl-\u003etotal_ev_rings; i++, mhi_event++) {\n 233:\t\t\tstruct mhi_ring *ring = \u0026mhi_event-\u003ering;\n 234:\t\n 235:\t\t\t/* Skip if this is an offload or HW event */\n 236:\t\t\tif (mhi_event-\u003eoffload_ev || mhi_event-\u003ehw_ring)\n 237:\t\t\t\tcontinue;\n 238:\t\n 239:\t\t\tring-\u003ewp = ring-\u003ebase + ring-\u003elen - ring-\u003eel_size;\n 240:\t\t\t*ring-\u003ectxt_wp = cpu_to_le64(ring-\u003eiommu_base + ring-\u003elen - ring-\u003eel_size);\n 241:\t\t\t/* Update all cores */\n 242:\t\t\tsmp_wmb();\n 243:\t\n 244:\t\t\t/* Ring the event ring db */\n 245:\t\t\tspin_lock_irq(\u0026mhi_event-\u003elock);\n 246:\t\t\tmhi_ring_er_db(mhi_event);\n 247:\t\t\tspin_unlock_irq(\u0026mhi_event-\u003elock);\n 248:\t\t}\n 249:\t\n 250:\t\t/* Set MHI to M0 state */\n 251:\t\tmhi_set_mhi_state(mhi_cntrl, MHI_STATE_M0);\n 252:\t\tread_unlock_bh(\u0026mhi_cntrl-\u003epm_lock);\n 253:\t\n 254:\t\treturn 0;\n 255:\t\n 256:\terror_mmio:\n 257:\t\tread_unlock_bh(\u0026mhi_cntrl-\u003epm_lock);\n 258:\t\n 259:\t\treturn -EIO;\n 260:\t}\n 261:\t\n 262:\tint mhi_pm_m0_transition(struct mhi_controller *mhi_cntrl)\n 263:\t{\n 264:\t\tenum mhi_pm_state cur_state;\n 265:\t\tstruct mhi_chan *mhi_chan;\n 266:\t\tstruct device *dev = \u0026mhi_cntrl-\u003emhi_dev-\u003edev;\n 267:\t\tint i;\n 268:\t\n 269:\t\twrite_lock_irq(\u0026mhi_cntrl-\u003epm_lock);\n"
}

gemini-3.1-pro-preview

null

null

							input: 35274
							output: 23
							thoughts: 114
						

**Analyzing the MHI State Transition**

Okay, so the initial state is set to `MHI_STATE_M0`. My immediate question is, what triggers the move to `DEV_ST_TRANSITION_MISSION_MODE`? Digging into it, I see `mhi_set_mhi_state` writes to the `MHICTRL` register. Right, that's the trigger. Then, the device is *supposed* to generate an interrupt, signaling the state change to M0. The host, hopefully, processes *that* interrupt and queues `DEV_ST_TRANSITION_MISSION_MODE`. I need to confirm that sequence. To understand this properly, I should check the logic within `mhi_pm_m0_transition`. That's where the heart of this transition probably lies.

{
  "Expression": "mhi_pm_m0_transition"
}

{
  "Output": "drivers/bus/mhi/host/internal.h=338=int mhi_ready_state_transition(struct mhi_controller *mhi_cntrl);\ndrivers/bus/mhi/host/internal.h:339:int mhi_pm_m0_transition(struct mhi_controller *mhi_cntrl);\ndrivers/bus/mhi/host/internal.h-340-void mhi_pm_m1_transition(struct mhi_controller *mhi_cntrl);\n--\ndrivers/bus/mhi/host/main.c=799=int mhi_process_ctrl_ev_ring(struct mhi_controller *mhi_cntrl,\n--\ndrivers/bus/mhi/host/main.c-861-\t\t\tcase MHI_STATE_M0:\ndrivers/bus/mhi/host/main.c:862:\t\t\t\tmhi_pm_m0_transition(mhi_cntrl);\ndrivers/bus/mhi/host/main.c-863-\t\t\t\tbreak;\n--\ndrivers/bus/mhi/host/pm.c=170=int mhi_ready_state_transition(struct mhi_controller *mhi_cntrl)\n--\ndrivers/bus/mhi/host/pm.c-261-\ndrivers/bus/mhi/host/pm.c:262:int mhi_pm_m0_transition(struct mhi_controller *mhi_cntrl)\ndrivers/bus/mhi/host/pm.c-263-{\n"
}

gemini-3.1-pro-preview

null

null

							input: 35970
							output: 24
							thoughts: 158
						

**My Analysis of Potential Vulnerability**

Okay, so I'm looking at how this `mhi_process_ctrl_ev_ring` function handles device events. It's clear that it's the critical piece that deals with events originating from the device. Specifically, when the device signals an `MHI_STATE_M0` event, `mhi_pm_m0_transition` gets called. Now, how exactly does the device trigger these events? Ah, right – the device writes data to an event ring in host memory, and then it triggers an interrupt.

That's where things get interesting. I'm thinking about Syzkaller and its PCI fuzzing capabilities. It can generate MSI/MSI-X interrupts and, crucially, write to host memory. This means it has the potential to inject a control event, and even force an `MHI_STATE_M0` transition.

The next thing I'm wondering is about `DEV_ST_TRANSITION_MISSION_MODE`. I need to figure out how and where that code is queued. That might be the path to something more concerning. I will check where that is queued.

{
  "Expression": "DEV_ST_TRANSITION_MISSION_MODE"
}

{
  "Output": "drivers/bus/mhi/host/internal.h=82=enum dev_st_transition {\n--\ndrivers/bus/mhi/host/internal.h-85-\tDEV_ST_TRANSITION_SBL,\ndrivers/bus/mhi/host/internal.h:86:\tDEV_ST_TRANSITION_MISSION_MODE,\ndrivers/bus/mhi/host/internal.h-87-\tDEV_ST_TRANSITION_FP,\n--\ndrivers/bus/mhi/host/main.c=799=int mhi_process_ctrl_ev_ring(struct mhi_controller *mhi_cntrl,\n--\ndrivers/bus/mhi/host/main.c-905-\t\t\tcase MHI_EE_AMSS:\ndrivers/bus/mhi/host/main.c:906:\t\t\t\tst = DEV_ST_TRANSITION_MISSION_MODE;\ndrivers/bus/mhi/host/main.c-907-\t\t\t\tbreak;\n--\ndrivers/bus/mhi/host/pm.c=798=void mhi_pm_st_worker(struct work_struct *work)\n--\ndrivers/bus/mhi/host/pm.c-837-\t\t\tbreak;\ndrivers/bus/mhi/host/pm.c:838:\t\tcase DEV_ST_TRANSITION_MISSION_MODE:\ndrivers/bus/mhi/host/pm.c-839-\t\t\tmhi_pm_mission_mode_transition(mhi_cntrl);\n"
}

gemini-3.1-pro-preview

null

null

							input: 36774
							output: 20
							thoughts: 585
						

**Fuzzing the MHI WWAN Control Driver: A Strategy Evaluation**

Okay, so I've confirmed that the `mhi_process_ctrl_ev_ring` function handles an EE change event destined for `MHI_EE_AMSS`, and then queues `DEV_ST_TRANSITION_MISSION_MODE`. This is promising! The PCI fuzzer *should* be able to trigger this sequence. By writing a specific event to the event ring and injecting an interrupt, I can potentially reach code within the MHI WWAN control driver in a virtualized environment. That opens the door to effective fuzzing.

Now, I need to be careful. The documentation explicitly mentions drivers in vendor-specific PCIe switches, SmartNICs, or GPUs, and notes that these often *require* physical hardware that isn't emulated in standard QEMU. Is MHI considered one of these? It's Qualcomm's protocol and isn't typically emulated within a standard QEMU setup. But, here's the crucial point: syzkaller's PCI fuzzer *can* reach it because it does emulate the PCI interface and can inject interrupts and DMA writes. This is the deciding factor.

Does the fact that syzkaller's PCI fuzzer can access it mean it *doesn't* "require physical hardware"? Usually, those tricky drivers with complex firmware interactions, like GPUs and SmartNICs, are tough to fuzz deeply because the fuzzer has to accurately guess the sequence of DMA rings and interrupts. But, syzkaller does manage to fuzz some PCI drivers. I'm going to lean towards "no, it doesn't require physical hardware".

Hold on! The WWAN core changes are also accessible through `wwan_hwsim`! I've got to revisit `wwan_hwsim.c`. Ah, `wwan_hwsim` creates WWAN ports, but it doesn't implement the `dtr_rts` callback, which is exactly the callback that the patch looks for. The patch modifies `wwan_core.c` to call `dtr_rts` *if* it's implemented.

```c
+		if (port->type == WWAN_PORT_AT && port->ops->dtr_rts) {
```

If `wwan_hwsim` doesn't provide the implementation, that code is bypassed. So, to fuzz the `dtr_rts` logic within `wwan_core.c`, I *need* a driver that implements `dtr_rts`. That's looking like `mhi_wwan_ctrl`.

Can `mhi_wwan_ctrl` be fuzzed? Even if the PCI fuzzer struggles with the MHI initialization, syzkaller might have existing descriptions for MHI or WWAN that would help bypass the initialization.

Finally, I need to be thorough. Are there any *other* drivers implementing `dtr_rts`? I need to make sure I haven't missed anything. I'll need to double check to see if any others have it implemented.

{
  "Expression": "\\.dtr_rts"
}

{
  "Output": "drivers/ipack/devices/ipoctal.c=267=static const struct tty_port_operations ipoctal_tty_port_ops = {\ndrivers/ipack/devices/ipoctal.c:268:\t.dtr_rts = NULL,\ndrivers/ipack/devices/ipoctal.c-269-\t.activate = ipoctal_port_activate,\n--\ndrivers/mmc/core/sdio_uart.c=989=static const struct tty_port_operations sdio_uart_port_ops = {\ndrivers/mmc/core/sdio_uart.c:990:\t.dtr_rts = uart_dtr_rts,\ndrivers/mmc/core/sdio_uart.c-991-\t.carrier_raised = uart_carrier_raised,\n--\ndrivers/net/wwan/mhi_wwan_ctrl.c=246=static const struct wwan_port_ops wwan_pops = {\n--\ndrivers/net/wwan/mhi_wwan_ctrl.c-249-\t.tx = mhi_wwan_ctrl_tx,\ndrivers/net/wwan/mhi_wwan_ctrl.c:250:\t.dtr_rts = mhi_wwan_ctrl_dtr_rts,\ndrivers/net/wwan/mhi_wwan_ctrl.c-251-};\n--\ndrivers/staging/greybus/uart.c=797=static const struct tty_port_operations gb_port_ops = {\ndrivers/staging/greybus/uart.c:798:\t.dtr_rts =\t\tgb_tty_dtr_rts,\ndrivers/staging/greybus/uart.c-799-\t.activate =\t\tgb_tty_port_activate,\n--\ndrivers/tty/amiserial.c=1476=static const struct tty_port_operations amiga_port_ops = {\ndrivers/tty/amiserial.c-1477-\t.carrier_raised = amiga_carrier_raised,\ndrivers/tty/amiserial.c:1478:\t.dtr_rts = amiga_dtr_rts,\ndrivers/tty/amiserial.c-1479-};\n--\ndrivers/tty/hvc/hvc_iucv.c=1011=static const struct hv_ops hvc_iucv_ops = {\n--\ndrivers/tty/hvc/hvc_iucv.c-1016-\t.notifier_hangup = hvc_iucv_notifier_hangup,\ndrivers/tty/hvc/hvc_iucv.c:1017:\t.dtr_rts = hvc_iucv_dtr_rts,\ndrivers/tty/hvc/hvc_iucv.c-1018-};\n--\ndrivers/tty/moxa.c=551=static const struct tty_port_operations moxa_port_ops = {\ndrivers/tty/moxa.c-552-\t.carrier_raised = moxa_carrier_raised,\ndrivers/tty/moxa.c:553:\t.dtr_rts = moxa_dtr_rts,\ndrivers/tty/moxa.c-554-\t.shutdown = moxa_shutdown,\n--\ndrivers/tty/mxser.c=1663=static const struct tty_port_operations mxser_port_ops = {\ndrivers/tty/mxser.c-1664-\t.carrier_raised = mxser_carrier_raised,\ndrivers/tty/mxser.c:1665:\t.dtr_rts = mxser_dtr_rts,\ndrivers/tty/mxser.c-1666-\t.activate = mxser_activate,\n--\ndrivers/tty/n_gsm.c=4272=static const struct tty_port_operations gsm_port_ops = {\ndrivers/tty/n_gsm.c-4273-\t.carrier_raised = gsm_carrier_raised,\ndrivers/tty/n_gsm.c:4274:\t.dtr_rts = gsm_dtr_rts,\ndrivers/tty/n_gsm.c-4275-\t.destruct = gsm_dlci_free,\n--\ndrivers/tty/serial/serial_core.c=2704=static const struct tty_port_operations uart_port_ops = {\ndrivers/tty/serial/serial_core.c-2705-\t.carrier_raised = uart_carrier_raised,\ndrivers/tty/serial/serial_core.c:2706:\t.dtr_rts\t= uart_dtr_rts,\ndrivers/tty/serial/serial_core.c-2707-\t.activate\t= uart_port_activate,\n--\ndrivers/usb/class/cdc-acm.c=1143=static const struct tty_port_operations acm_port_ops = {\ndrivers/usb/class/cdc-acm.c:1144:\t.dtr_rts = acm_port_dtr_rts,\ndrivers/usb/class/cdc-acm.c-1145-\t.shutdown = acm_port_shutdown,\n--\ndrivers/usb/serial/ch341.c=865=static struct usb_serial_driver ch341_device = {\n--\ndrivers/usb/serial/ch341.c-871-\t.open              = ch341_open,\ndrivers/usb/serial/ch341.c:872:\t.dtr_rts\t   = ch341_dtr_rts,\ndrivers/usb/serial/ch341.c-873-\t.carrier_raised\t   = ch341_carrier_raised,\n--\ndrivers/usb/serial/cp210x.c=301=static struct usb_serial_driver cp210x_device = {\n--\ndrivers/usb/serial/cp210x.c-323-\t.port_remove\t\t= cp210x_port_remove,\ndrivers/usb/serial/cp210x.c:324:\t.dtr_rts\t\t= cp210x_dtr_rts,\ndrivers/usb/serial/cp210x.c-325-\t.process_read_urb\t= cp210x_process_read_urb,\n--\ndrivers/usb/serial/cypress_m8.c=138=static struct usb_serial_driver cypress_earthmate_device = {\n--\ndrivers/usb/serial/cypress_m8.c-148-\t.close =\t\t\tcypress_close,\ndrivers/usb/serial/cypress_m8.c:149:\t.dtr_rts =\t\t\tcypress_dtr_rts,\ndrivers/usb/serial/cypress_m8.c-150-\t.write =\t\t\tcypress_write,\n--\ndrivers/usb/serial/cypress_m8.c=164=static struct usb_serial_driver cypress_hidcom_device = {\n--\ndrivers/usb/serial/cypress_m8.c-174-\t.close =\t\t\tcypress_close,\ndrivers/usb/serial/cypress_m8.c:175:\t.dtr_rts =\t\t\tcypress_dtr_rts,\ndrivers/usb/serial/cypress_m8.c-176-\t.write =\t\t\tcypress_write,\n--\ndrivers/usb/serial/cypress_m8.c=189=static struct usb_serial_driver cypress_ca42v2_device = {\n--\ndrivers/usb/serial/cypress_m8.c-199-\t.close =\t\t\tcypress_close,\ndrivers/usb/serial/cypress_m8.c:200:\t.dtr_rts =\t\t\tcypress_dtr_rts,\ndrivers/usb/serial/cypress_m8.c-201-\t.write =\t\t\tcypress_write,\n--\ndrivers/usb/serial/digi_acceleport.c=261=static struct usb_serial_driver digi_acceleport_2_device = {\n--\ndrivers/usb/serial/digi_acceleport.c-271-\t.close =\t\t\tdigi_close,\ndrivers/usb/serial/digi_acceleport.c:272:\t.dtr_rts =\t\t\tdigi_dtr_rts,\ndrivers/usb/serial/digi_acceleport.c-273-\t.write =\t\t\tdigi_write,\n--\ndrivers/usb/serial/f81232.c=982=static struct usb_serial_driver f81232_device = {\n--\ndrivers/usb/serial/f81232.c-991-\t.close =\t\tf81232_close,\ndrivers/usb/serial/f81232.c:992:\t.dtr_rts =\t\tf81232_dtr_rts,\ndrivers/usb/serial/f81232.c-993-\t.carrier_raised =\tf81232_carrier_raised,\n--\ndrivers/usb/serial/f81232.c=1008=static struct usb_serial_driver f81534a_device = {\n--\ndrivers/usb/serial/f81232.c-1015-\t.close =\t\tf81232_close,\ndrivers/usb/serial/f81232.c:1016:\t.dtr_rts =\t\tf81232_dtr_rts,\ndrivers/usb/serial/f81232.c-1017-\t.carrier_raised =\tf81232_carrier_raised,\n--\ndrivers/usb/serial/f81534.c=1538=static struct usb_serial_driver f81534_device = {\n--\ndrivers/usb/serial/f81534.c-1553-\t.break_ctl =\t\tf81534_break_ctl,\ndrivers/usb/serial/f81534.c:1554:\t.dtr_rts =\t\tf81534_dtr_rts,\ndrivers/usb/serial/f81534.c-1555-\t.process_read_urb =\tf81534_process_read_urb,\n--\ndrivers/usb/serial/ftdi_sio.c=2840=static struct usb_serial_driver ftdi_device = {\n--\ndrivers/usb/serial/ftdi_sio.c-2853-\t.open =\t\t\tftdi_open,\ndrivers/usb/serial/ftdi_sio.c:2854:\t.dtr_rts =\t\tftdi_dtr_rts,\ndrivers/usb/serial/ftdi_sio.c-2855-\t.throttle =\t\tusb_serial_generic_throttle,\n--\ndrivers/usb/serial/ipw.c=284=static struct usb_serial_driver ipw_device = {\n--\ndrivers/usb/serial/ipw.c-296-\t.port_remove =\t\tusb_wwan_port_remove,\ndrivers/usb/serial/ipw.c:297:\t.dtr_rts =\t\tipw_dtr_rts,\ndrivers/usb/serial/ipw.c-298-\t.write =\t\tusb_wwan_write,\n--\ndrivers/usb/serial/keyspan.c=3014=static struct usb_serial_driver keyspan_1port_device = {\n--\ndrivers/usb/serial/keyspan.c-3022-\t.close\t\t\t= keyspan_close,\ndrivers/usb/serial/keyspan.c:3023:\t.dtr_rts\t\t= keyspan_dtr_rts,\ndrivers/usb/serial/keyspan.c-3024-\t.write\t\t\t= keyspan_write,\n--\ndrivers/usb/serial/keyspan.c=3037=static struct usb_serial_driver keyspan_2port_device = {\n--\ndrivers/usb/serial/keyspan.c-3045-\t.close\t\t\t= keyspan_close,\ndrivers/usb/serial/keyspan.c:3046:\t.dtr_rts\t\t= keyspan_dtr_rts,\ndrivers/usb/serial/keyspan.c-3047-\t.write\t\t\t= keyspan_write,\n--\ndrivers/usb/serial/keyspan.c=3060=static struct usb_serial_driver keyspan_4port_device = {\n--\ndrivers/usb/serial/keyspan.c-3068-\t.close\t\t\t= keyspan_close,\ndrivers/usb/serial/keyspan.c:3069:\t.dtr_rts\t\t= keyspan_dtr_rts,\ndrivers/usb/serial/keyspan.c-3070-\t.write\t\t\t= keyspan_write,\n--\ndrivers/usb/serial/keyspan_pda.c=711=static struct usb_serial_driver keyspan_pda_device = {\n--\ndrivers/usb/serial/keyspan_pda.c-719-\t.num_interrupt_in =\t1,\ndrivers/usb/serial/keyspan_pda.c:720:\t.dtr_rts =\t\tkeyspan_pda_dtr_rts,\ndrivers/usb/serial/keyspan_pda.c-721-\t.open =\t\t\tkeyspan_pda_open,\n--\ndrivers/usb/serial/mct_u232.c=68=static struct usb_serial_driver mct_u232_device = {\n--\ndrivers/usb/serial/mct_u232.c-76-\t.close =\t     mct_u232_close,\ndrivers/usb/serial/mct_u232.c:77:\t.dtr_rts =\t     mct_u232_dtr_rts,\ndrivers/usb/serial/mct_u232.c-78-\t.throttle =\t     mct_u232_throttle,\n--\ndrivers/usb/serial/mxuport.c=1286=static struct usb_serial_driver mxuport_device = {\n--\ndrivers/usb/serial/mxuport.c-1309-\t.tiocmset\t\t= mxuport_tiocmset,\ndrivers/usb/serial/mxuport.c:1310:\t.dtr_rts\t\t= mxuport_dtr_rts,\ndrivers/usb/serial/mxuport.c-1311-\t.process_read_urb\t= mxuport_process_read_urb,\n--\ndrivers/usb/serial/option.c=2558=static struct usb_serial_driver option_1port_device = {\n--\ndrivers/usb/serial/option.c-2567-\t.close             = usb_wwan_close,\ndrivers/usb/serial/option.c:2568:\t.dtr_rts\t   = usb_wwan_dtr_rts,\ndrivers/usb/serial/option.c-2569-\t.write             = usb_wwan_write,\n--\ndrivers/usb/serial/pl2303.c=1271=static struct usb_serial_driver pl2303_device = {\n--\ndrivers/usb/serial/pl2303.c-1282-\t.close =\t\tpl2303_close,\ndrivers/usb/serial/pl2303.c:1283:\t.dtr_rts =\t\tpl2303_dtr_rts,\ndrivers/usb/serial/pl2303.c-1284-\t.carrier_raised =\tpl2303_carrier_raised,\n--\ndrivers/usb/serial/qcserial.c=456=static struct usb_serial_driver qcdevice = {\n--\ndrivers/usb/serial/qcserial.c-465-\t.close\t\t     = usb_wwan_close,\ndrivers/usb/serial/qcserial.c:466:\t.dtr_rts\t     = usb_wwan_dtr_rts,\ndrivers/usb/serial/qcserial.c-467-\t.write\t\t     = usb_wwan_write,\n--\ndrivers/usb/serial/quatech2.c=923=static struct usb_serial_driver qt2_device = {\n--\ndrivers/usb/serial/quatech2.c-938-\t.port_remove         = qt2_port_remove,\ndrivers/usb/serial/quatech2.c:939:\t.dtr_rts             = qt2_dtr_rts,\ndrivers/usb/serial/quatech2.c-940-\t.break_ctl           = qt2_break_ctl,\n--\ndrivers/usb/serial/sierra.c=1022=static struct usb_serial_driver sierra_device = {\n--\ndrivers/usb/serial/sierra.c-1031-\t.close             = sierra_close,\ndrivers/usb/serial/sierra.c:1032:\t.dtr_rts\t   = sierra_dtr_rts,\ndrivers/usb/serial/sierra.c-1033-\t.write             = sierra_write,\n--\ndrivers/usb/serial/spcp8x5.c=451=static struct usb_serial_driver spcp8x5_device = {\n--\ndrivers/usb/serial/spcp8x5.c-459-\t.open\t\t\t= spcp8x5_open,\ndrivers/usb/serial/spcp8x5.c:460:\t.dtr_rts\t\t= spcp8x5_dtr_rts,\ndrivers/usb/serial/spcp8x5.c-461-\t.carrier_raised\t\t= spcp8x5_carrier_raised,\n--\ndrivers/usb/serial/ssu100.c=499=static struct usb_serial_driver ssu100_device = {\n--\ndrivers/usb/serial/ssu100.c-509-\t.port_remove         = ssu100_port_remove,\ndrivers/usb/serial/ssu100.c:510:\t.dtr_rts             = ssu100_dtr_rts,\ndrivers/usb/serial/ssu100.c-511-\t.process_read_urb    = ssu100_process_read_urb,\n--\ndrivers/usb/serial/upd78f0730.c=408=static struct usb_serial_driver upd78f0730_device = {\n--\ndrivers/usb/serial/upd78f0730.c-420-\t.tiocmset\t= upd78f0730_tiocmset,\ndrivers/usb/serial/upd78f0730.c:421:\t.dtr_rts\t= upd78f0730_dtr_rts,\ndrivers/usb/serial/upd78f0730.c-422-\t.break_ctl\t= upd78f0730_break_ctl,\n--\ndrivers/usb/serial/usb-serial.c=786=static const struct tty_port_operations serial_port_ops = {\ndrivers/usb/serial/usb-serial.c-787-\t.carrier_raised\t\t= serial_port_carrier_raised,\ndrivers/usb/serial/usb-serial.c:788:\t.dtr_rts\t\t= serial_port_dtr_rts,\ndrivers/usb/serial/usb-serial.c-789-\t.activate\t\t= serial_port_activate,\n--\ndrivers/usb/serial/xr_serial.c=1084=static struct usb_serial_driver xr_device = {\n--\ndrivers/usb/serial/xr_serial.c-1099-\t.ioctl\t\t\t= xr_ioctl,\ndrivers/usb/serial/xr_serial.c:1100:\t.dtr_rts\t\t= xr_dtr_rts\ndrivers/usb/serial/xr_serial.c-1101-};\n"
}

gemini-3.1-pro-preview

null

null

							input: 43128
							output: 22
							thoughts: 860
						

**Fuzzing Strategy for DTR/RTS Signaling in WWAN Core and MHI Driver**

Okay, so I've been digging into this patch. My initial thought was to look at `dtr_rts` being added, but it looks like it's a callback within `wwan_port_ops`, not the more generic `tty_port_operations` or `usb_serial_driver` structures, which is an important distinction. The patch introduces this new `dtr_rts` function pointer to `wwan_port_ops` and I need to identify which driver uses this.

A quick `grep` for `.dtr_rts` within `wwan_port_ops` tells me that `mhi_wwan_ctrl.c` is the only one using it. So, to effectively fuzz the changes within `wwan_core.c` that this patch introduces, I need to ensure that the `mhi_wwan_ctrl` driver is being probed and active. Thankfully, the PCI fuzzer, emulating the MHI controller, should handle that.

Is this fuzzing effort worthwhile? Absolutely. It touches new logic within the WWAN core *and* introduces a new MHI driver specifically for handling DTR/RTS signaling. This driver, named `mhi_wwan_dtr_driver`, binds to the "IP_CTRL" channel. The key function here is `mhi_wwan_ctrl_send_dtr`, which is responsible for sending messages over this channel. This is definitely a reachable entry point.

Now, let's identify the specific symbols I need to focus on for fuzzing:

*   `mhi_wwan_ctrl_send_dtr`
*   `mhi_wwan_ctrl_dtr_rts`
*   `mhi_wwan_dtr_probe`
*   `mhi_wwan_dtr_remove`
*   `mhi_wwan_dtr_ul_xfer_cb`
*   `mhi_wwan_dtr_dl_xfer_cb`
*   `wwan_port_op_start` (the patched version)
*   `wwan_port_op_stop` (the patched version)
*   `wwan_port_fops_at_ioctl` (the patched version)

Next, I need to consider the instructions. The preference is for non-static, non-inlined API entrypoints to fuzz, which is correct. I have to make sure that even static symbols are included if they're used as callbacks, because those aren't typically inlined. Therefore, I'll definitely include:

*   `mhi_wwan_ctrl_dtr_rts` (static, callback)
*   `mhi_wwan_dtr_probe` (static, callback)
*   `mhi_wwan_dtr_remove` (static, callback)
*   `mhi_wwan_dtr_ul_xfer_cb` (static, callback)
*   `mhi_wwan_dtr_dl_xfer_cb` (static, callback)
*   `wwan_port_fops_at_ioctl` (static, callback)
*   `wwan_port_op_start` (static, callback)
*   `wwan_port_op_stop` (static, callback)
*   `wwan_remove_port` (exported)

Hold on, I need to confirm that `wwan_port_op_start` and `wwan_port_op_stop`, are also callbacks. It looks like they're called from `wwan_port_fops_open` and `wwan_port_fops_release`, so they should be on the list.
I need to check how `wwan_port_op_start` is used.

{
  "Expression": "wwan_port_op_start"
}

{
  "Output": "drivers/net/wwan/wwan_core.c=86=struct wwan_port {\n--\ndrivers/net/wwan/wwan_core.c-106-\ndrivers/net/wwan/wwan_core.c:107:static int wwan_port_op_start(struct wwan_port *port);\ndrivers/net/wwan/wwan_core.c-108-static void wwan_port_op_stop(struct wwan_port *port);\n--\ndrivers/net/wwan/wwan_core.c=506=static int wwan_gnss_open(struct gnss_device *gdev)\ndrivers/net/wwan/wwan_core.c-507-{\ndrivers/net/wwan/wwan_core.c:508:\treturn wwan_port_op_start(gnss_get_drvdata(gdev));\ndrivers/net/wwan/wwan_core.c-509-}\n--\ndrivers/net/wwan/wwan_core.c=746=EXPORT_SYMBOL_GPL(wwan_port_get_drvdata);\ndrivers/net/wwan/wwan_core.c-747-\ndrivers/net/wwan/wwan_core.c:748:static int wwan_port_op_start(struct wwan_port *port)\ndrivers/net/wwan/wwan_core.c-749-{\n--\ndrivers/net/wwan/wwan_core.c=866=static int wwan_port_fops_open(struct inode *inode, struct file *file)\n--\ndrivers/net/wwan/wwan_core.c-877-\ndrivers/net/wwan/wwan_core.c:878:\terr = wwan_port_op_start(port);\ndrivers/net/wwan/wwan_core.c-879-\tif (err)\n"
}

gemini-3.1-pro-preview

null

null

							input: 45359
							output: 17
							thoughts: 403
						

**Analyzing WWAN Port Operations**

Okay, so I'm digging into this `wwan_port_op_start` function and trying to understand its role. It's declared as static, which is interesting. My initial thought was that it's likely an inlined function. However, the more I look at it, the more I'm leaning toward it *not* being inlined, as it seems a bit substantial in size. To get a handle on the key areas, I'll shift my focus to the related callbacks and exported functions. Listing those out will provide a clearer picture.

Specifically, I need to zero in on these functions: `mhi_wwan_dtr_probe`, `mhi_wwan_dtr_remove`, `mhi_wwan_dtr_ul_xfer_cb`, `mhi_wwan_dtr_dl_xfer_cb`, `mhi_wwan_ctrl_dtr_rts`, `wwan_remove_port`, and `wwan_port_fops_at_ioctl`. These should be the core elements to understand.

Next, I need to examine the associated configurations. I'm focusing on `MHI_BUS`, `MHI_BUS_PCI_GENERIC`, `WWAN`, and `MHI_WWAN_CTRL`. Let me double-check if `MHI_WWAN_CTRL` has any additional dependencies. Looks like it depends on `MHI_BUS`. `WWAN` is a menuconfig, which means it must be explicitly enabled. Now, `MHI_BUS_PCI_GENERIC` depends on both `MHI_BUS` and `PCI`. So, to be clear, here's my configuration list: `MHI_BUS`, `MHI_BUS_PCI_GENERIC`, `WWAN`, and `MHI_WWAN_CTRL`.

Now, I want to make sure I have the exact configuration name for `MHI_WWAN_CTRL`. Just to be safe, I'm checking, and yep, it's `config MHI_WWAN_CTRL`. Okay, now I need to verify that `WWAN` is the right config.

{
  "Expression": "config WWAN"
}

{
  "Output": "drivers/net/wwan/Kconfig=6=menu \"Wireless WAN\"\ndrivers/net/wwan/Kconfig-7-\ndrivers/net/wwan/Kconfig:8:config WWAN\ndrivers/net/wwan/Kconfig-9-\ttristate \"WWAN Driver Core\"\n--\ndrivers/net/wwan/Kconfig=18=if WWAN\ndrivers/net/wwan/Kconfig-19-\ndrivers/net/wwan/Kconfig:20:config WWAN_DEBUGFS\ndrivers/net/wwan/Kconfig-21-\tbool \"WWAN devices debugfs interface\" if EXPERT\n--\ndrivers/net/wwan/Kconfig-30-\ndrivers/net/wwan/Kconfig:31:config WWAN_HWSIM\ndrivers/net/wwan/Kconfig-32-\ttristate \"Simulated WWAN device\"\n"
}

gemini-3.1-pro-preview

null

null

							input: 46476
							output: 19
							thoughts: 26
						

Okay, here's my interpretation of those thoughts, summarized from a first-person perspective, assuming I'm well-versed in the subject:

**Navigating the Architecture**

Alright, so the architecture I'm working with is fundamentally centered around the `WWAN` component. That much is clear. Now, I need to pinpoint the details of its connection and how it communicates. I'm reasonably confident, but let's just double-check that `MHI_BUS` is indeed the correct and specific name of the relevant bus. Better to be precise from the start to avoid later complications.

{
  "Expression": "config MHI_BUS"
}

{
  "Output": "drivers/bus/mhi/ep/Kconfig:1:config MHI_BUS_EP\ndrivers/bus/mhi/ep/Kconfig-2-\ttristate \"Modem Host Interface (MHI) bus Endpoint implementation\"\n--\ndrivers/bus/mhi/host/Kconfig-7-\ndrivers/bus/mhi/host/Kconfig:8:config MHI_BUS\ndrivers/bus/mhi/host/Kconfig-9-\ttristate \"Modem Host Interface (MHI) bus\"\n--\ndrivers/bus/mhi/host/Kconfig-15-\ndrivers/bus/mhi/host/Kconfig:16:config MHI_BUS_DEBUG\ndrivers/bus/mhi/host/Kconfig-17-\tbool \"Debugfs support for the MHI bus\"\n--\ndrivers/bus/mhi/host/Kconfig-23-\ndrivers/bus/mhi/host/Kconfig:24:config MHI_BUS_PCI_GENERIC\ndrivers/bus/mhi/host/Kconfig-25-\ttristate \"MHI PCI controller driver\"\n"
}

gemini-3.1-pro-preview

null

null

							input: 46920
							output: 319
							thoughts: 1252
						

**DTR/RTS Signal Implementation for MHI WWAN**

Okay, so I'm looking at this patch and, yes, it's focusing on `MHI_BUS`. It adds DTR/RTS signaling to the WWAN core and specifically implements it for the MHI WWAN control driver. The patch introduces a new MHI driver, `mhi_wwan_dtr_driver`, which is binding to the "IP_CTRL" channel for sending and receiving these DTR/RTS messages. I know the MHI bus, along with the PCI controller driver (`mhi_pci_generic`), can be targeted with syzkaller's PCI fuzzer. This is useful because we can emulate the MHI controller's registers and event rings to potentially trigger device creation. The changes to the WWAN core are reachable through the WWAN character devices, which is the expected entry point.

I need to confirm which symbols are important here. The EnableConfigs are as expected. I've noted the `MHI_BUS`, `MHI_BUS_PCI_GENERIC`, `WWAN`, and `MHI_WWAN_CTRL` configurations. Then I have the following list of symbols I need to check in depth: `mhi_wwan_dtr_probe`, `mhi_wwan_dtr_remove`, `mhi_wwan_dtr_ul_xfer_cb`, `mhi_wwan_dtr_dl_xfer_cb`, `mhi_wwan_ctrl_dtr_rts`, `wwan_remove_port`, and `wwan_port_fops_at_ioctl`. These should be the core building blocks of this feature.

Now, let's confirm the modifications to the core WWAN functions. I confirmed that `wwan_remove_port` is, in fact, exported and modified. I also saw that `wwan_port_fops_at_ioctl` is modified, which makes sense. I had to look at `wwan_port_op_start` and `wwan_port_op_stop`, since these were also touched. I'll add them to the symbols list just to be sure that they are not inlined. So here is the final list of critical symbols: `mhi_wwan_dtr_probe`, `mhi_wwan_dtr_remove`, `mhi_wwan_dtr_ul_xfer_cb`, `mhi_wwan_dtr_dl_xfer_cb`, `mhi_wwan_ctrl_dtr_rts`, `wwan_remove_port`, `wwan_port_fops_at_ioctl`, `wwan_port_op_start`, and `wwan_port_op_stop`. I think this should cover it.

{
  "EnableConfigs": [
    "MHI_BUS",
    "MHI_BUS_PCI_GENERIC",
    "WWAN",
    "MHI_WWAN_CTRL"
  ],
  "FocusSymbols": [
    "mhi_wwan_dtr_probe",
    "mhi_wwan_dtr_remove",
    "mhi_wwan_dtr_ul_xfer_cb",
    "mhi_wwan_dtr_dl_xfer_cb",
    "mhi_wwan_ctrl_dtr_rts",
    "wwan_remove_port",
    "wwan_port_fops_at_ioctl",
    "wwan_port_op_start",
    "wwan_port_op_stop"
  ],
  "Reasoning": "The patch adds DTR/RTS signaling support to the WWAN core and implements it for the MHI WWAN control driver. It introduces a new MHI driver `mhi_wwan_dtr_driver` that binds to the \"IP_CTRL\" channel to send and receive DTR/RTS messages. The MHI bus and its PCI controller driver (`mhi_pci_generic`) can be fuzzed using syzkaller's PCI fuzzer, which can emulate the MHI controller's registers and event rings to trigger device creation. The WWAN core changes are reachable via the WWAN character devices.",
  "WorthFuzzing": true
}

{
  "EnableConfigs": [
    "MHI_BUS",
    "MHI_BUS_PCI_GENERIC",
    "WWAN",
    "MHI_WWAN_CTRL"
  ],
  "FocusSymbols": [
    "mhi_wwan_dtr_probe",
    "mhi_wwan_dtr_remove",
    "mhi_wwan_dtr_ul_xfer_cb",
    "mhi_wwan_dtr_dl_xfer_cb",
    "mhi_wwan_ctrl_dtr_rts",
    "wwan_remove_port",
    "wwan_port_fops_at_ioctl",
    "wwan_port_op_start",
    "wwan_port_op_stop"
  ],
  "Reasoning": "The patch adds DTR/RTS signaling support to the WWAN core and implements it for the MHI WWAN control driver. It introduces a new MHI driver `mhi_wwan_dtr_driver` that binds to the \"IP_CTRL\" channel to send and receive DTR/RTS messages. The MHI bus and its PCI controller driver (`mhi_pci_generic`) can be fuzzed using syzkaller's PCI fuzzer, which can emulate the MHI controller's registers and event rings to trigger device creation. The WWAN core changes are reachable via the WWAN character devices.",
  "WorthFuzzing": true
}

{
  "WorthFuzzing": true
}

null

best-expensive

null

{
  "KMSANReasoning": "The patch introduces a new feature to signal DTR/RTS lines over the IP_CTRL channel in the MHI WWAN CTRL driver. It allocates a new message structure `struct mhi_dtr_ctrl_msg` using `kzalloc_obj`, which guarantees that the allocated memory is fully zero-initialized. The structure is also marked as `__packed`, eliminating any potential padding bytes. The message is then populated with data and sent to the device via `mhi_queue_buf`. Since the memory is fully initialized before being sent, there is no risk of exposing uninitialized memory to the device or userspace. The receive buffer `rx_buf` is used as a sink for `DMA_FROM_DEVICE` and is also part of a zero-initialized structure (`dtr` allocated via `kzalloc_obj`). It does not send uninitialized memory. Any potential memory safety issues, such as out-of-bounds accesses or use-after-free bugs, would be caught by standard KASAN and other bug detectors. Therefore, a dedicated KMSAN fuzzing session is not required.",
  "NeedsKMSAN": false
}

You are an expert Linux kernel security engineer specializing in kernel memory
error detectors (KASAN and KMSAN). Your job is to review the provided patch series and
determine if the code changes justify spawning a dedicated KMSAN (KernelMemorySanitizer)
fuzzing session in addition to standard KASAN fuzzing.

CRITICAL DISTINCTION BETWEEN KASAN AND KMSAN:
- Standard KASAN kernel builds (upstream-apparmor-kasan.config) already enable
  a comprehensive suite of debugging tools and sanitizers, including KASAN
  (out-of-bounds accesses, use-after-free, double free, invalid free), LOCKDEP
  (locking bugs and deadlocks), UB-sanitizers, and memory corruption checks.
- KMSAN (KernelMemorySanitizer) detects reads of UNINITIALIZED memory (stack, heap,
  or page allocations) and kernel-to-user memory info-leaks.

Rule: THERE IS NO SENSE IN RUNNING A KMSAN SESSION IF A BUG CAN BE CAUGHT BY KASAN,
LOCKDEP, OR OTHER STANDARD BUG DETECTORS.
A dedicated KMSAN fuzzing session incurs significant resource costs. You must ONLY
set NeedsKMSAN=true if the code changes introduce or expose UNINITIALIZED MEMORY risks
that are detected ONLY by KMSAN.

Look holistically at the patch series and surrounding code. Even if no direct
uninitialized field accesses or new buffer allocations are added in the diff itself,
a patch may alter control flow, bounds checking, or data length calculations in ways
that change how the rest of the code operates on existing buffers (e.g. allowing
uninitialized stack/heap memory to be read, copied to user space, or used in control
flow). Do not hesitate to use your code access tools to inspect the surrounding code,
called functions, and callers.

Set NeedsKMSAN=true ONLY IF the patch introduces or modifies:
1. Kernel structures sent to user space (via copy_to_user, put_user, netlink skb
   attributes, ioctl output arguments, socket options, or BPF buffers) where fields
   or structure padding might not be fully initialized/zeroed.
2. Conditional logic or branching that depends on potentially uninitialized variables
   or struct fields.
3. Allocation or initialization of complex data structures where uninitialized fields
   could be read later in reachable code paths.
4. Bounds checks, lengths, or logic in a way that allows surrounding code to access
   uninitialized bytes of existing buffers.

Set NeedsKMSAN=false IF:
- The code changes primarily risk out-of-bounds access, array overflows, NULL pointer
  dereferences, locking deadlocks, or use-after-free bugs (these are already caught
  by KASAN, LOCKDEP, or standard bug detectors).
- All stack/heap structures touched or introduced by the patch are fully zeroed
  or initialized (e.g. using = {0}, memset, kzalloc) before being read or copied.
- The patch does not introduce any risk of uninitialized memory usage or info-leaks.

Use your code access tools to inspect the surrounding code if necessary, then provide
detailed KMSANReasoning contrasting KASAN vs KMSAN applicability for this patch.
Prefer calling several tools at the same time to save round-trips.


Use set-results tool to provide results of the analysis.
It must be called exactly once before the final reply.
Ignore results of this tool.

For your convenience, here is the diff of the changes:
commit bccfd7fceb0f5ff3027b8976586907c5038dbdec
Author: syz-cluster <triage@syzkaller.com>
Date:   Wed Aug 19 23:21:27 2026 +0000

    syz-cluster: applied patch under review

diff --git a/drivers/bus/mhi/host/pci_generic.c b/drivers/bus/mhi/host/pci_generic.c
index 0d0d9c7ffa4bf..ba47dd153837e 100644
--- a/drivers/bus/mhi/host/pci_generic.c
+++ b/drivers/bus/mhi/host/pci_generic.c
@@ -728,6 +728,8 @@ static const struct mhi_channel_config mhi_sierra_em919x_channels[] = {
 	MHI_CHANNEL_CONFIG_DL(13, "MBIM", 128, 0),
 	MHI_CHANNEL_CONFIG_UL(14, "QMI", 32, 0),
 	MHI_CHANNEL_CONFIG_DL(15, "QMI", 32, 0),
+	MHI_CHANNEL_CONFIG_UL(18, "IP_CTRL", 32, 0),
+	MHI_CHANNEL_CONFIG_DL(19, "IP_CTRL", 32, 0),
 	MHI_CHANNEL_CONFIG_UL(32, "DUN", 32, 0),
 	MHI_CHANNEL_CONFIG_DL(33, "DUN", 32, 0),
 	MHI_CHANNEL_CONFIG_HW_UL(100, "IP_HW0", 512, 1),
diff --git a/drivers/net/wwan/mhi_wwan_ctrl.c b/drivers/net/wwan/mhi_wwan_ctrl.c
index a31d8540fbb85..1cb91b59256e9 100644
--- a/drivers/net/wwan/mhi_wwan_ctrl.c
+++ b/drivers/net/wwan/mhi_wwan_ctrl.c
@@ -1,8 +1,12 @@
 // SPDX-License-Identifier: GPL-2.0-only
 /* Copyright (c) 2021, Linaro Ltd <loic.poulain@linaro.org> */
 #include <linux/kernel.h>
+#include <linux/list.h>
 #include <linux/mhi.h>
 #include <linux/module.h>
+#include <linux/mutex.h>
+#include <linux/slab.h>
+#include <linux/termios.h>
 #include <linux/wwan.h>
 
 /* MHI wwan flags */
@@ -14,6 +18,31 @@ enum mhi_wwan_flags {
 
 #define MHI_WWAN_MAX_MTU	0x8000
 
+/* IP_CTRL channel message that sets the modem's DTR/RTS control lines */
+struct mhi_dtr_ctrl_msg {
+	__le32 preamble;
+	__le32 msg_id;
+	__le32 dest_id;
+	__le32 size;
+	__le32 msg;
+} __packed;
+
+#define MHI_DTR_CTRL_MAGIC	0x4C525443	/* 'CTRL' */
+#define MHI_DTR_MSG_DTR		BIT(0)
+#define MHI_DTR_MSG_RTS		BIT(1)
+#define MHI_DTR_HOST_STATE	0x10
+
+/* Per-controller IP_CTRL channel, used to signal DTR/RTS to that modem */
+struct mhi_wwan_dtr {
+	struct mhi_controller *cntrl;
+	struct mhi_device *mhi_dev;
+	struct list_head node;
+	u8 rx_buf[sizeof(struct mhi_dtr_ctrl_msg)]; /* sink for modem serial-state DL */
+};
+
+static LIST_HEAD(mhi_wwan_dtr_list);
+static DEFINE_MUTEX(mhi_wwan_dtr_lock);
+
 struct mhi_wwan_dev {
 	/* Lower level is a mhi dev, upper level is a wwan port */
 	struct mhi_device *mhi_dev;
@@ -103,6 +132,61 @@ static void mhi_wwan_ctrl_refill_work(struct work_struct *work)
 	}
 }
 
+/* Signal the modem's DTR/RTS lines over its own controller's IP_CTRL channel */
+static int mhi_wwan_ctrl_send_dtr(struct mhi_wwan_dev *mhiwwan, unsigned int mdmbits)
+{
+	struct mhi_controller *cntrl = mhiwwan->mhi_dev->mhi_cntrl;
+	struct mhi_device *ctrl_dev = NULL;
+	struct mhi_dtr_ctrl_msg *dtr_msg;
+	struct mhi_wwan_dtr *dtr;
+	u32 msg = 0;
+	int ret;
+
+	guard(mutex)(&mhi_wwan_dtr_lock);
+
+	list_for_each_entry(dtr, &mhi_wwan_dtr_list, node) {
+		if (dtr->cntrl == cntrl) {
+			ctrl_dev = dtr->mhi_dev;
+			break;
+		}
+	}
+	if (!ctrl_dev) {
+		dev_dbg(&mhiwwan->mhi_dev->dev,
+			"IP_CTRL not enumerated; DTR/RTS not signalled to modem\n");
+		return 0;
+	}
+
+	dtr_msg = kzalloc_obj(*dtr_msg);
+	if (!dtr_msg)
+		return -ENOMEM;
+
+	if (mdmbits & TIOCM_DTR)
+		msg |= MHI_DTR_MSG_DTR;
+	if (mdmbits & TIOCM_RTS)
+		msg |= MHI_DTR_MSG_RTS;
+
+	dtr_msg->preamble = cpu_to_le32(MHI_DTR_CTRL_MAGIC);
+	dtr_msg->msg_id = cpu_to_le32(MHI_DTR_HOST_STATE);
+	dtr_msg->dest_id = cpu_to_le32(mhiwwan->mhi_dev->ul_chan_id);
+	dtr_msg->size = cpu_to_le32(sizeof(__le32));
+	dtr_msg->msg = cpu_to_le32(msg);
+
+	ret = mhi_queue_buf(ctrl_dev, DMA_TO_DEVICE, dtr_msg, sizeof(*dtr_msg),
+			    MHI_EOT);
+	if (ret) {
+		dev_dbg(&mhiwwan->mhi_dev->dev,
+			"failed to queue DTR/RTS signal: %d\n", ret);
+		kfree(dtr_msg);
+	}
+
+	return ret;
+}
+
+static void mhi_wwan_ctrl_dtr_rts(struct wwan_port *port, unsigned int mdmbits)
+{
+	mhi_wwan_ctrl_send_dtr(wwan_port_get_drvdata(port), mdmbits);
+}
+
 static int mhi_wwan_ctrl_start(struct wwan_port *port)
 {
 	struct mhi_wwan_dev *mhiwwan = wwan_port_get_drvdata(port);
@@ -163,6 +247,7 @@ static const struct wwan_port_ops wwan_pops = {
 	.start = mhi_wwan_ctrl_start,
 	.stop = mhi_wwan_ctrl_stop,
 	.tx = mhi_wwan_ctrl_tx,
+	.dtr_rts = mhi_wwan_ctrl_dtr_rts,
 };
 
 static void mhi_ul_xfer_cb(struct mhi_device *mhi_dev,
@@ -255,6 +340,71 @@ static void mhi_wwan_ctrl_remove(struct mhi_device *mhi_dev)
 	kfree(mhiwwan);
 }
 
+/* IP_CTRL channel driver, bound separately so the data-port path is untouched */
+static void mhi_wwan_dtr_ul_xfer_cb(struct mhi_device *mhi_dev,
+				    struct mhi_result *mhi_result)
+{
+	/* MHI core has done with the buffer, release it */
+	kfree(mhi_result->buf_addr);
+}
+
+static void mhi_wwan_dtr_dl_xfer_cb(struct mhi_device *mhi_dev,
+				    struct mhi_result *mhi_result)
+{
+	struct mhi_wwan_dtr *dtr = dev_get_drvdata(&mhi_dev->dev);
+
+	/* Modem serial state not needed; requeue the sink buffer to keep DL ring live */
+	mhi_queue_buf(mhi_dev, DMA_FROM_DEVICE, dtr->rx_buf,
+		      sizeof(dtr->rx_buf), MHI_EOT);
+}
+
+static int mhi_wwan_dtr_probe(struct mhi_device *mhi_dev,
+			      const struct mhi_device_id *id)
+{
+	struct mhi_wwan_dtr *dtr;
+	int ret;
+
+	dtr = kzalloc_obj(*dtr);
+	if (!dtr)
+		return -ENOMEM;
+
+	ret = mhi_prepare_for_transfer(mhi_dev);
+	if (ret) {
+		kfree(dtr);
+		return ret;
+	}
+
+	dtr->cntrl = mhi_dev->mhi_cntrl;
+	dtr->mhi_dev = mhi_dev;
+	dev_set_drvdata(&mhi_dev->dev, dtr);
+
+	ret = mhi_queue_buf(mhi_dev, DMA_FROM_DEVICE, dtr->rx_buf,
+			    sizeof(dtr->rx_buf), MHI_EOT);
+	if (ret) {
+		mhi_unprepare_from_transfer(mhi_dev);
+		kfree(dtr);
+		return ret;
+	}
+
+	mutex_lock(&mhi_wwan_dtr_lock);
+	list_add(&dtr->node, &mhi_wwan_dtr_list);
+	mutex_unlock(&mhi_wwan_dtr_lock);
+
+	return 0;
+}
+
+static void mhi_wwan_dtr_remove(struct mhi_device *mhi_dev)
+{
+	struct mhi_wwan_dtr *dtr = dev_get_drvdata(&mhi_dev->dev);
+
+	mutex_lock(&mhi_wwan_dtr_lock);
+	list_del(&dtr->node);
+	mutex_unlock(&mhi_wwan_dtr_lock);
+
+	mhi_unprepare_from_transfer(mhi_dev);
+	kfree(dtr);
+}
+
 static const struct mhi_device_id mhi_wwan_ctrl_match_table[] = {
 	{ .chan = "DUN", .driver_data = WWAN_PORT_AT },
 	{ .chan = "DUN2", .driver_data = WWAN_PORT_AT },
@@ -278,7 +428,45 @@ static struct mhi_driver mhi_wwan_ctrl_driver = {
 	},
 };
 
-module_mhi_driver(mhi_wwan_ctrl_driver);
+static const struct mhi_device_id mhi_wwan_dtr_match_table[] = {
+	{ .chan = "IP_CTRL" },
+	{},
+};
+MODULE_DEVICE_TABLE(mhi, mhi_wwan_dtr_match_table);
+
+static struct mhi_driver mhi_wwan_dtr_driver = {
+	.id_table = mhi_wwan_dtr_match_table,
+	.remove = mhi_wwan_dtr_remove,
+	.probe = mhi_wwan_dtr_probe,
+	.ul_xfer_cb = mhi_wwan_dtr_ul_xfer_cb,
+	.dl_xfer_cb = mhi_wwan_dtr_dl_xfer_cb,
+	.driver = {
+		.name = "mhi_wwan_dtr",
+	},
+};
+
+static int __init mhi_wwan_ctrl_init(void)
+{
+	int ret;
+
+	ret = mhi_driver_register(&mhi_wwan_dtr_driver);
+	if (ret)
+		return ret;
+
+	ret = mhi_driver_register(&mhi_wwan_ctrl_driver);
+	if (ret)
+		mhi_driver_unregister(&mhi_wwan_dtr_driver);
+
+	return ret;
+}
+module_init(mhi_wwan_ctrl_init);
+
+static void __exit mhi_wwan_ctrl_exit(void)
+{
+	mhi_driver_unregister(&mhi_wwan_ctrl_driver);
+	mhi_driver_unregister(&mhi_wwan_dtr_driver);
+}
+module_exit(mhi_wwan_ctrl_exit);
 
 MODULE_LICENSE("GPL v2");
 MODULE_DESCRIPTION("MHI WWAN CTRL Driver");
diff --git a/drivers/net/wwan/wwan_core.c b/drivers/net/wwan/wwan_core.c
index ffbcf11e4e681..3a6a0c5a3acf4 100644
--- a/drivers/net/wwan/wwan_core.c
+++ b/drivers/net/wwan/wwan_core.c
@@ -685,6 +685,12 @@ void wwan_remove_port(struct wwan_port *port)
 
 	mutex_lock(&port->ops_lock);
 	if (port->start_count) {
+		if (port->type == WWAN_PORT_AT && port->ops->dtr_rts) {
+			mutex_lock(&port->data_lock);
+			port->at_data.mdmbits &= ~(TIOCM_DTR | TIOCM_RTS);
+			mutex_unlock(&port->data_lock);
+			port->ops->dtr_rts(port, 0);
+		}
 		port->ops->stop(port);
 		port->start_count = 0;
 	}
@@ -759,8 +765,17 @@ static int wwan_port_op_start(struct wwan_port *port)
 	if (!port->start_count)
 		ret = port->ops->start(port);
 
-	if (!ret)
+	if (!ret) {
 		port->start_count++;
+		/* Mirror TTY semantics: raise DTR/RTS on first open of an AT port */
+		if (port->start_count == 1 && port->type == WWAN_PORT_AT &&
+		    port->ops->dtr_rts) {
+			mutex_lock(&port->data_lock);
+			port->at_data.mdmbits |= TIOCM_DTR | TIOCM_RTS;
+			mutex_unlock(&port->data_lock);
+			port->ops->dtr_rts(port, port->at_data.mdmbits);
+		}
+	}
 
 out_unlock:
 	mutex_unlock(&port->ops_lock);
@@ -773,6 +788,13 @@ static void wwan_port_op_stop(struct wwan_port *port)
 	mutex_lock(&port->ops_lock);
 	port->start_count--;
 	if (!port->start_count) {
+		/* Mirror TTY semantics: drop DTR/RTS on last close of an AT port */
+		if (port->ops && port->type == WWAN_PORT_AT && port->ops->dtr_rts) {
+			mutex_lock(&port->data_lock);
+			port->at_data.mdmbits &= ~(TIOCM_DTR | TIOCM_RTS);
+			mutex_unlock(&port->data_lock);
+			port->ops->dtr_rts(port, port->at_data.mdmbits);
+		}
 		if (port->ops)
 			port->ops->stop(port);
 		skb_queue_purge(&port->rxq);
@@ -980,6 +1002,7 @@ static long wwan_port_fops_at_ioctl(struct wwan_port *port, unsigned int cmd,
 				    unsigned long arg)
 {
 	int ret = 0;
+	bool call_dtr_rts = false;
 
 	mutex_lock(&port->data_lock);
 
@@ -1036,6 +1059,8 @@ static long wwan_port_fops_at_ioctl(struct wwan_port *port, unsigned int cmd,
 			port->at_data.mdmbits |= mdmbits;
 		else
 			port->at_data.mdmbits = mdmbits;
+		if (port->type == WWAN_PORT_AT)
+			call_dtr_rts = true;
 		break;
 	}
 
@@ -1061,6 +1086,19 @@ static long wwan_port_fops_at_ioctl(struct wwan_port *port, unsigned int cmd,
 
 	mutex_unlock(&port->data_lock);
 
+	if (call_dtr_rts) {
+		unsigned int bits;
+
+		mutex_lock(&port->ops_lock);
+		if (port->ops && port->ops->dtr_rts) {
+			mutex_lock(&port->data_lock);
+			bits = port->at_data.mdmbits;
+			mutex_unlock(&port->data_lock);
+			port->ops->dtr_rts(port, bits);
+		}
+		mutex_unlock(&port->ops_lock);
+	}
+
 	return ret;
 }
 
diff --git a/include/linux/wwan.h b/include/linux/wwan.h
index 1e0e2cb535799..57406139304ea 100644
--- a/include/linux/wwan.h
+++ b/include/linux/wwan.h
@@ -57,6 +57,8 @@ struct wwan_port;
  * @tx_blocking: Optional blocking routine that sends WWAN port protocol data
  *               to the device.
  * @tx_poll: Optional routine that sets additional TX poll flags.
+ * @dtr_rts: Optional routine that updates the modem control lines to match
+ *           @mdmbits (a TIOCM_* bitmask). Only called for WWAN_PORT_AT ports.
  *
  * The wwan_port_ops structure contains a list of low-level operations
  * that control a WWAN port device. All functions are mandatory unless specified.
@@ -70,6 +72,7 @@ struct wwan_port_ops {
 	int (*tx_blocking)(struct wwan_port *port, struct sk_buff *skb);
 	__poll_t (*tx_poll)(struct wwan_port *port, struct file *filp,
 			    poll_table *wait);
+	void (*dtr_rts)(struct wwan_port *port, unsigned int mdmbits);
 };
 
 /** struct wwan_port_caps - The WWAN port capbilities

gemini-3.1-pro-preview

null

null

							input: 6792
							output: 18
							thoughts: 603
						

**My Initial Thoughts on the MHI WWAN CTRL Driver Patch**

Okay, so this patch introduces a new feature to the MHI WWAN CTRL driver: signaling DTR/RTS lines over the IP_CTRL channel. That's a reasonable addition. They've defined a new `mhi_dtr_ctrl_msg` struct, and it looks like they're sending this message to the device via `mhi_queue_buf`. Let's dig into the `mhi_wwan_ctrl_send_dtr` function to see how it works.

Right away, I see `dtr_msg = kzalloc_obj(*dtr_msg);`. Hold on a second... `kzalloc_obj`? Is that a standard macro? I don't recall seeing that in the mainline kernel. I'm pretty sure I'd remember that. Let me double-check my mental database... Nope, that's not a standard Linux kernel macro. Wait, is it a local definition? I'm not familiar with that one. Maybe it's `kzalloc(sizeof(*dtr_msg), GFP_KERNEL)`? That seems more plausible. Let's see if it's defined anywhere in the project.

Okay, I'm checking, and it definitely looks like `kzalloc_obj` isn't in the standard kernel. Hmm, is this a recent addition or a typo? I need to grep for it just to be sure. Alright, I can see it in the patch. So, it's either a macro specific to this project or a custom helper. Regardless, the intent is clear: it allocates memory and initializes it to zero. Okay, that's good. At least there shouldn't be any uninitialized memory issues.

I'm a little concerned about that non-standard macro, but let's keep going. It looks like they're setting up the message fields: `preamble`, `msg_id`, `dest_id`, `size`, and the actual `msg` which contains the DTR/RTS bit flags. Then it's being queued to the device using `mhi_queue_buf` with `DMA_TO_DEVICE` and `MHI_EOT`, all pretty standard stuff.

Let's quickly check `mhi_wwan_dtr_probe` just to see if they use it there as well. Wait, yep, `dtr = kzalloc_obj(*dtr);` again! So it looks like it is defined as a non-standard helper, and I am not missing something I should be familiar with. Alright, the memory allocation is the first thing that catches my attention because I am used to using the `kzalloc` function instead. Let me keep looking.

{
  "Expression": "kzalloc_obj"
}

{
  "Output": "\nFull output is too long, showing 500 out of 79249 lines.\nUse more precise expression if possible.\n\nDocumentation/core-api/list.rst=103=list:\n--\nDocumentation/core-api/list.rst-114-\nDocumentation/core-api/list.rst:115:          grock = kzalloc_obj(*grock);\nDocumentation/core-api/list.rst-116-          if (!grock)\n--\nDocumentation/core-api/list.rst-125-\nDocumentation/core-api/list.rst:126:          dimitri = kzalloc_obj(*dimitri);\nDocumentation/core-api/list.rst-127-          if (!dimitri)\n--\nDocumentation/driver-api/mailbox.rst=45=a message and a callback function to the API and return immediately).\n--\nDocumentation/driver-api/mailbox.rst-89-\nDocumentation/driver-api/mailbox.rst:90:\t\tdc_sync = kzalloc_obj(*dc_sync);\nDocumentation/driver-api/mailbox.rst:91:\t\tdc_async = kzalloc_obj(*dc_async);\nDocumentation/driver-api/mailbox.rst-92-\n--\nDocumentation/driver-api/media/v4l2-fh.rst=26=Example:\n--\nDocumentation/driver-api/media/v4l2-fh.rst-44-\nDocumentation/driver-api/media/v4l2-fh.rst:45:\t\tmy_fh = kzalloc_obj(*my_fh);\nDocumentation/driver-api/media/v4l2-fh.rst-46-\n--\nDocumentation/process/coding-style.rst=938=The kernel provides the following general purpose memory allocators:\nDocumentation/process/coding-style.rst:939:kmalloc(), kzalloc(), kmalloc_objs(), kzalloc_objs(), vmalloc(), and\nDocumentation/process/coding-style.rst-940-vzalloc().  Please refer to the API documentation for further information\n--\nDocumentation/process/coding-style.rst=964=The preferred form for allocating a zeroed array is the following:\n--\nDocumentation/process/coding-style.rst-967-\nDocumentation/process/coding-style.rst:968:\tp = kzalloc_objs(*p, n, ...);\nDocumentation/process/coding-style.rst-969-\n--\nDocumentation/process/deprecated.rst=398=become, respectively::\n--\nDocumentation/process/deprecated.rst-400-\tptr = kmalloc_obj(*ptr [, gfp] );\nDocumentation/process/deprecated.rst:401:\tptr = kzalloc_obj(*ptr [, gfp] );\nDocumentation/process/deprecated.rst-402-\tptr = kmalloc_objs(*ptr, count [, gfp] );\nDocumentation/process/deprecated.rst:403:\tptr = kzalloc_objs(*ptr, count [, gfp] );\nDocumentation/process/deprecated.rst-404-\tptr = kmalloc_flex(*ptr, flex_member, count [, gfp] );\n--\nDocumentation/sound/kernel-api/writing-an-alsa-driver.rst=208=to details explained in the following section.\n--\nDocumentation/sound/kernel-api/writing-an-alsa-driver.rst-268-              /* allocate a chip-specific data with zero filled */\nDocumentation/sound/kernel-api/writing-an-alsa-driver.rst:269:              chip = kzalloc_obj(*chip);\nDocumentation/sound/kernel-api/writing-an-alsa-driver.rst-270-              if (chip == NULL)\n--\nDocumentation/sound/kernel-api/writing-an-alsa-driver.rst=623=After allocating a card instance via :c:func:`snd_card_new()`\n--\nDocumentation/sound/kernel-api/writing-an-alsa-driver.rst-630-  .....\nDocumentation/sound/kernel-api/writing-an-alsa-driver.rst:631:  chip = kzalloc_obj(*chip);\nDocumentation/sound/kernel-api/writing-an-alsa-driver.rst-632-\n--\nDocumentation/sound/kernel-api/writing-an-alsa-driver.rst=698=destructor and PCI entries. Example code is shown first, below::\n--\nDocumentation/sound/kernel-api/writing-an-alsa-driver.rst-749-\nDocumentation/sound/kernel-api/writing-an-alsa-driver.rst:750:              chip = kzalloc_obj(*chip);\nDocumentation/sound/kernel-api/writing-an-alsa-driver.rst-751-              if (chip == NULL) {\n--\nDocumentation/sound/kernel-api/writing-an-alsa-driver.rst=3823=chip data individually::\n--\nDocumentation/sound/kernel-api/writing-an-alsa-driver.rst-3835-          ....\nDocumentation/sound/kernel-api/writing-an-alsa-driver.rst:3836:          chip = kzalloc_obj(*chip);\nDocumentation/sound/kernel-api/writing-an-alsa-driver.rst-3837-          ....\n--\nDocumentation/translations/zh_CN/video4linux/v4l2-framework.txt=794=int my_open(struct file *file)\n--\nDocumentation/translations/zh_CN/video4linux/v4l2-framework.txt-801-\nDocumentation/translations/zh_CN/video4linux/v4l2-framework.txt:802:\tmy_fh = kzalloc_obj(*my_fh);\nDocumentation/translations/zh_CN/video4linux/v4l2-framework.txt-803-\n--\narch/alpha/kernel/module.c=64=module_frob_arch_sections(Elf64_Ehdr *hdr, Elf64_Shdr *sechdrs,\n--\narch/alpha/kernel/module.c-95-\tnsyms = symtab-\u003esh_size / sizeof(Elf64_Sym);\narch/alpha/kernel/module.c:96:\tchains = kzalloc_objs(struct got_entry, nsyms);\narch/alpha/kernel/module.c-97-\tif (!chains) {\n--\narch/alpha/kernel/setup.c=390=register_cpus(void)\n--\narch/alpha/kernel/setup.c-394-\tfor_each_possible_cpu(i) {\narch/alpha/kernel/setup.c:395:\t\tstruct cpu *p = kzalloc_obj(*p);\narch/alpha/kernel/setup.c-396-\t\tif (!p)\n--\narch/arc/net/bpf_jit_core.c=1120=static int jit_prepare_final_mem_alloc(struct jit_context *ctx)\n--\narch/arc/net/bpf_jit_core.c-1131-\tif (ctx-\u003eneed_extra_pass) {\narch/arc/net/bpf_jit_core.c:1132:\t\tctx-\u003ejit_data = kzalloc_obj(*ctx-\u003ejit_data);\narch/arc/net/bpf_jit_core.c-1133-\t\tif (!ctx-\u003ejit_data)\n--\narch/arm/common/locomo.c=220=locomo_init_one_child(struct locomo *lchip, struct locomo_dev_info *info)\n--\narch/arm/common/locomo.c-224-\narch/arm/common/locomo.c:225:\tdev = kzalloc_obj(struct locomo_dev);\narch/arm/common/locomo.c-226-\tif (!dev) {\n--\narch/arm/common/locomo.c=356=__locomo_probe(struct device *me, struct resource *mem, int irq)\n--\narch/arm/common/locomo.c-362-\narch/arm/common/locomo.c:363:\tlchip = kzalloc_obj(struct locomo);\narch/arm/common/locomo.c-364-\tif (!lchip)\n--\narch/arm/common/sa1111.c=733=sa1111_init_one_child(struct sa1111 *sachip, struct resource *parent,\n--\narch/arm/common/sa1111.c-739-\narch/arm/common/sa1111.c:740:\tdev = kzalloc_obj(struct sa1111_dev);\narch/arm/common/sa1111.c-741-\tif (!dev) {\n--\narch/arm/common/scoop.c=178=static int scoop_probe(struct platform_device *pdev)\n--\narch/arm/common/scoop.c-187-\narch/arm/common/scoop.c:188:\tdevptr = kzalloc_obj(struct scoop_dev);\narch/arm/common/scoop.c-189-\tif (!devptr)\n--\narch/arm/kernel/smp.c=108=static int secondary_biglittle_prepare(unsigned int cpu)\n--\narch/arm/kernel/smp.c-110-\tif (!cpu_vtable[cpu])\narch/arm/kernel/smp.c:111:\t\tcpu_vtable[cpu] = kzalloc_obj(*cpu_vtable[cpu]);\narch/arm/kernel/smp.c-112-\n--\narch/arm/kernel/vdso.c=169=static int __init vdso_init(void)\n--\narch/arm/kernel/vdso.c-181-\t/* Allocate the VDSO text pagelist */\narch/arm/kernel/vdso.c:182:\tvdso_text_pagelist = kzalloc_objs(struct page *, text_pages);\narch/arm/kernel/vdso.c-183-\tif (vdso_text_pagelist == NULL)\n--\narch/arm/mach-footbridge/dc21285.c=261=int __init dc21285_setup(int nr, struct pci_sys_data *sys)\n--\narch/arm/mach-footbridge/dc21285.c-264-\narch/arm/mach-footbridge/dc21285.c:265:\tres = kzalloc_objs(struct resource, 2);\narch/arm/mach-footbridge/dc21285.c-266-\tif (!res) {\n--\narch/arm/mach-footbridge/ebsa285.c=69=static int __init ebsa285_leds_init(void)\n--\narch/arm/mach-footbridge/ebsa285.c-86-\narch/arm/mach-footbridge/ebsa285.c:87:\t\tled = kzalloc_obj(*led);\narch/arm/mach-footbridge/ebsa285.c-88-\t\tif (!led)\n--\narch/arm/mach-footbridge/netwinder-hw.c=720=static int __init netwinder_leds_init(void)\n--\narch/arm/mach-footbridge/netwinder-hw.c-729-\narch/arm/mach-footbridge/netwinder-hw.c:730:\t\tled = kzalloc_obj(*led);\narch/arm/mach-footbridge/netwinder-hw.c-731-\t\tif (!led)\n--\narch/arm/mach-imx/mmdc.c=473=static int imx_mmdc_perf_init(struct platform_device *pdev, void __iomem *mmdc_base,\n--\narch/arm/mach-imx/mmdc.c-479-\narch/arm/mach-imx/mmdc.c:480:\tpmu_mmdc = kzalloc_obj(*pmu_mmdc);\narch/arm/mach-imx/mmdc.c-481-\tif (!pmu_mmdc) {\n--\narch/arm/mach-mvebu/board-v7.c=114=static void __init i2c_quirk(void)\n--\narch/arm/mach-mvebu/board-v7.c-129-\narch/arm/mach-mvebu/board-v7.c:130:\t\tnew_compat = kzalloc_obj(*new_compat);\narch/arm/mach-mvebu/board-v7.c-131-\n--\narch/arm/mach-mvebu/coherency.c=163=static void __init armada_375_380_coherency_init(struct device_node *np)\n--\narch/arm/mach-mvebu/coherency.c-187-\narch/arm/mach-mvebu/coherency.c:188:\t\tp = kzalloc_obj(*p);\narch/arm/mach-mvebu/coherency.c-189-\t\tp-\u003ename = kstrdup(\"arm,io-coherent\", GFP_KERNEL);\n--\narch/arm/mach-mvebu/mvebu-soc-id.c=148=static int __init mvebu_soc_device(void)\n--\narch/arm/mach-mvebu/mvebu-soc-id.c-156-\narch/arm/mach-mvebu/mvebu-soc-id.c:157:\tsoc_dev_attr = kzalloc_obj(*soc_dev_attr);\narch/arm/mach-mvebu/mvebu-soc-id.c-158-\tif (!soc_dev_attr)\n--\narch/arm/mach-mxs/mach-mxs.c=380=static void __init mxs_machine_init(void)\n--\narch/arm/mach-mxs/mach-mxs.c-389-\narch/arm/mach-mxs/mach-mxs.c:390:\tsoc_dev_attr = kzalloc_obj(*soc_dev_attr);\narch/arm/mach-mxs/mach-mxs.c-391-\tif (!soc_dev_attr)\n--\narch/arm/mach-omap1/dma.c=294=static int __init omap1_system_dma_init(void)\n--\narch/arm/mach-omap1/dma.c-321-\narch/arm/mach-omap1/dma.c:322:\td = kzalloc_obj(*d);\narch/arm/mach-omap1/dma.c-323-\tif (!d) {\n--\narch/arm/mach-omap1/mcbsp.c=292=static void omap_mcbsp_register_board_cfg(struct resource *res, int res_count,\n--\narch/arm/mach-omap1/mcbsp.c-296-\narch/arm/mach-omap1/mcbsp.c:297:\tomap_mcbsp_devices = kzalloc_objs(struct platform_device *, size);\narch/arm/mach-omap1/mcbsp.c-298-\tif (!omap_mcbsp_devices) {\n--\narch/arm/mach-omap1/timer.c=51=static int __init omap1_dm_timer_init(void)\n--\narch/arm/mach-omap1/timer.c-127-\narch/arm/mach-omap1/timer.c:128:\t\tpdata = kzalloc_obj(*pdata);\narch/arm/mach-omap1/timer.c-129-\t\tif (!pdata) {\n--\narch/arm/mach-omap2/clkt2xxx_virt_prcm_set.c=230=void omap2xxx_clkt_vps_init(void)\n--\narch/arm/mach-omap2/clkt2xxx_virt_prcm_set.c-239-\narch/arm/mach-omap2/clkt2xxx_virt_prcm_set.c:240:\thw = kzalloc_obj(*hw);\narch/arm/mach-omap2/clkt2xxx_virt_prcm_set.c-241-\tif (!hw)\n--\narch/arm/mach-omap2/id.c=786=void __init omap_soc_device_init(void)\n--\narch/arm/mach-omap2/id.c-790-\narch/arm/mach-omap2/id.c:791:\tsoc_dev_attr = kzalloc_obj(*soc_dev_attr);\narch/arm/mach-omap2/id.c-792-\tif (!soc_dev_attr)\n--\narch/arm/mach-omap2/omap_device.c=131=static int omap_device_build_from_dt(struct platform_device *pdev)\n--\narch/arm/mach-omap2/omap_device.c-158-\narch/arm/mach-omap2/omap_device.c:159:\thwmods = kzalloc_objs(struct omap_hwmod *, oh_cnt);\narch/arm/mach-omap2/omap_device.c-160-\tif (!hwmods) {\n--\narch/arm/mach-omap2/omap_hwmod.c=3381=static int omap_hwmod_allocate_module(struct device *dev, struct omap_hwmod *oh,\n--\narch/arm/mach-omap2/omap_hwmod.c-3394-\narch/arm/mach-omap2/omap_hwmod.c:3395:\tsysc = kzalloc_obj(*sysc);\narch/arm/mach-omap2/omap_hwmod.c-3396-\tif (!sysc)\n--\narch/arm/mach-omap2/omap_hwmod.c-3424-\tif (list_empty(\u0026oh-\u003eslave_ports)) {\narch/arm/mach-omap2/omap_hwmod.c:3425:\t\toi = kzalloc_obj(*oi);\narch/arm/mach-omap2/omap_hwmod.c-3426-\t\tif (!oi)\n--\narch/arm/mach-omap2/omap_hwmod.c=3513=int omap_hwmod_init_module(struct device *dev,\n--\narch/arm/mach-omap2/omap_hwmod.c-3527-\tif (!oh) {\narch/arm/mach-omap2/omap_hwmod.c:3528:\t\toh = kzalloc_obj(*oh);\narch/arm/mach-omap2/omap_hwmod.c-3529-\t\tif (!oh)\n--\narch/arm/mach-omap2/omap_hwmod.c-3538-\narch/arm/mach-omap2/omap_hwmod.c:3539:\t\toh-\u003eclass = kzalloc_obj(*oh-\u003eclass);\narch/arm/mach-omap2/omap_hwmod.c-3540-\t\tif (!oh-\u003eclass) {\n--\narch/arm/mach-omap2/pm33xx-core.c=379=static int __init amx3_idle_init(struct device_node *cpu_node, int cpu)\n--\narch/arm/mach-omap2/pm33xx-core.c-412-\narch/arm/mach-omap2/pm33xx-core.c:413:\tidle_states = kzalloc_objs(*idle_states, state_count);\narch/arm/mach-omap2/pm33xx-core.c-414-\tif (!idle_states)\n--\narch/arm/mach-omap2/sr_device.c=30=static void __init sr_set_nvalues(struct omap_volt_data *volt_data,\n--\narch/arm/mach-omap2/sr_device.c-41-\narch/arm/mach-omap2/sr_device.c:42:\tnvalue_table = kzalloc_objs(*nvalue_table, count);\narch/arm/mach-omap2/sr_device.c-43-\tif (!nvalue_table)\n--\narch/arm/mach-orion5x/pci.c=139=static int __init pcie_setup(struct pci_sys_data *sys)\n--\narch/arm/mach-orion5x/pci.c-171-\t */\narch/arm/mach-orion5x/pci.c:172:\tres = kzalloc_obj(struct resource);\narch/arm/mach-orion5x/pci.c-173-\tif (!res)\n--\narch/arm/mach-orion5x/pci.c=466=static int __init pci_setup(struct pci_sys_data *sys)\n--\narch/arm/mach-orion5x/pci.c-492-\t */\narch/arm/mach-orion5x/pci.c:493:\tres = kzalloc_obj(struct resource);\narch/arm/mach-orion5x/pci.c-494-\tif (!res)\n--\narch/arm/mach-rpc/ecard.c=689=static struct expansion_card *__init ecard_alloc_card(int type, int slot)\n--\narch/arm/mach-rpc/ecard.c-694-\narch/arm/mach-rpc/ecard.c:695:\tec = kzalloc_obj(ecard_t);\narch/arm/mach-rpc/ecard.c-696-\tif (!ec) {\n--\narch/arm/mach-sa1100/clock.c=93=int __init sa11xx_clk_init(void)\n--\narch/arm/mach-sa1100/clock.c-109-\narch/arm/mach-sa1100/clock.c:110:\thw = kzalloc_obj(*hw);\narch/arm/mach-sa1100/clock.c-111-\tif (!hw)\n--\narch/arm/mach-sa1100/clock.c-131-\narch/arm/mach-sa1100/clock.c:132:\thw = kzalloc_obj(*hw);\narch/arm/mach-sa1100/clock.c-133-\tif (!hw)\n--\narch/arm/mach-sa1100/generic.c=317=int __init sa11x0_register_fixed_regulator(int n,\n--\narch/arm/mach-sa1100/generic.c-323-\narch/arm/mach-sa1100/generic.c:324:\tcfg-\u003einit_data = id = kzalloc_obj(*cfg-\u003einit_data);\narch/arm/mach-sa1100/generic.c-325-\tif (!cfg-\u003einit_data)\n--\narch/arm/mach-sa1100/neponset.c=225=static int neponset_probe(struct platform_device *dev)\n--\narch/arm/mach-sa1100/neponset.c-278-\narch/arm/mach-sa1100/neponset.c:279:\td = kzalloc_obj(*d);\narch/arm/mach-sa1100/neponset.c-280-\tif (!d) {\n--\narch/arm/mach-shmobile/regulator-quirk-rcar-gen2.c=141=static int __init rcar_gen2_regulator_quirk(void)\n--\narch/arm/mach-shmobile/regulator-quirk-rcar-gen2.c-166-\narch/arm/mach-shmobile/regulator-quirk-rcar-gen2.c:167:\t\tquirk = kzalloc_obj(*quirk);\narch/arm/mach-shmobile/regulator-quirk-rcar-gen2.c-168-\t\tif (!quirk) {\n--\narch/arm/mach-versatile/spc.c=393=static int ve_spc_populate_opps(uint32_t cluster)\n--\narch/arm/mach-versatile/spc.c-397-\narch/arm/mach-versatile/spc.c:398:\topps = kzalloc_objs(*opps, MAX_OPPS);\narch/arm/mach-versatile/spc.c-399-\tif (!opps)\n--\narch/arm/mach-versatile/spc.c=442=int __init ve_spc_init(void __iomem *baseaddr, u32 a15_clusid, int irq)\n--\narch/arm/mach-versatile/spc.c-444-\tint ret;\narch/arm/mach-versatile/spc.c:445:\tinfo = kzalloc_obj(*info);\narch/arm/mach-versatile/spc.c-446-\tif (!info)\n--\narch/arm/mach-versatile/spc.c=523=static struct clk *ve_spc_clk_register(struct device *cpu_dev)\n--\narch/arm/mach-versatile/spc.c-527-\narch/arm/mach-versatile/spc.c:528:\tspc = kzalloc_obj(*spc);\narch/arm/mach-versatile/spc.c-529-\tif (!spc)\n--\narch/arm/mach-versatile/versatile.c=123=static void __init versatile_dt_pci_init(void)\n--\narch/arm/mach-versatile/versatile.c-144-\narch/arm/mach-versatile/versatile.c:145:\tnewprop = kzalloc_obj(*newprop);\narch/arm/mach-versatile/versatile.c-146-\tif (!newprop)\n--\narch/arm/mach-zynq/common.c=105=static void __init zynq_init_machine(void)\n--\narch/arm/mach-zynq/common.c-110-\narch/arm/mach-zynq/common.c:111:\tsoc_dev_attr = kzalloc_obj(*soc_dev_attr);\narch/arm/mach-zynq/common.c-112-\tif (!soc_dev_attr)\n--\narch/arm/mm/cache-l2x0-pmu.c=503=static __init int l2x0_pmu_init(void)\n--\narch/arm/mm/cache-l2x0-pmu.c-509-\narch/arm/mm/cache-l2x0-pmu.c:510:\tl2x0_pmu = kzalloc_obj(*l2x0_pmu);\narch/arm/mm/cache-l2x0-pmu.c-511-\tif (!l2x0_pmu) {\n--\narch/arm/mm/cache-uniphier.c=315=static int __init __uniphier_cache_init(struct device_node *np,\n--\narch/arm/mm/cache-uniphier.c-344-\narch/arm/mm/cache-uniphier.c:345:\tdata = kzalloc_obj(*data);\narch/arm/mm/cache-uniphier.c-346-\tif (!data)\n--\narch/arm/mm/dma-mapping.c=533=static void *__dma_alloc(struct device *dev, size_t size, dma_addr_t *handle,\n--\narch/arm/mm/dma-mapping.c-560-\narch/arm/mm/dma-mapping.c:561:\tbuf = kzalloc_obj(*buf,\narch/arm/mm/dma-mapping.c-562-\t\t\t  gfp \u0026 ~(__GFP_DMA | __GFP_DMA32 | __GFP_HIGHMEM));\n--\narch/arm/mm/dma-mapping.c=1487=arm_iommu_create_mapping(struct device *dev, dma_addr_t base, u64 size)\n--\narch/arm/mm/dma-mapping.c-1506-\narch/arm/mm/dma-mapping.c:1507:\tmapping = kzalloc_obj(struct dma_iommu_mapping);\narch/arm/mm/dma-mapping.c-1508-\tif (!mapping)\n--\narch/arm/xen/enlighten.c=316=int __init arch_xen_unpopulated_init(struct resource **res)\n--\narch/arm/xen/enlighten.c-343-\narch/arm/xen/enlighten.c:344:\tregs = kzalloc_objs(*regs, nr_reg);\narch/arm/xen/enlighten.c-345-\tif (!regs) {\n--\narch/arm/xen/enlighten.c-387-\narch/arm/xen/enlighten.c:388:\t\ttmp_res = kzalloc_obj(*tmp_res);\narch/arm/xen/enlighten.c-389-\t\tif (!tmp_res) {\n--\narch/arm/xen/p2m.c=150=bool __set_phys_to_machine_multi(unsigned long pfn,\n--\narch/arm/xen/p2m.c-178-\narch/arm/xen/p2m.c:179:\tp2m_entry = kzalloc_obj(*p2m_entry, GFP_NOWAIT);\narch/arm/xen/p2m.c-180-\tif (!p2m_entry)\n--\narch/arm64/kernel/vdso.c=68=static int __init __vdso_init(enum vdso_abi abi)\n--\narch/arm64/kernel/vdso.c-83-\narch/arm64/kernel/vdso.c:84:\tvdso_pagelist = kzalloc_objs(struct page *, vdso_info[abi].vdso_pages);\narch/arm64/kernel/vdso.c-85-\tif (vdso_pagelist == NULL)\n--\narch/arm64/kvm/mmu.c=480=static int share_pfn_hyp(u64 pfn)\n--\narch/arm64/kvm/mmu.c-492-\narch/arm64/kvm/mmu.c:493:\tthis = kzalloc_obj(*this);\narch/arm64/kvm/mmu.c-494-\tif (!this) {\n--\narch/arm64/kvm/mmu.c=981=int kvm_init_stage2_mmu(struct kvm *kvm, struct kvm_s2_mmu *mmu, unsigned long type)\n--\narch/arm64/kvm/mmu.c-1007-\narch/arm64/kvm/mmu.c:1008:\tpgt = kzalloc_obj(*pgt, GFP_KERNEL_ACCOUNT);\narch/arm64/kvm/mmu.c-1009-\tif (!pgt)\n--\narch/arm64/kvm/mmu.c=1180=int topup_hyp_memcache(struct kvm_hyp_memcache *mc, unsigned long min_pages)\n--\narch/arm64/kvm/mmu.c-1185-\tif (!mc-\u003emapping) {\narch/arm64/kvm/mmu.c:1186:\t\tmc-\u003emapping = kzalloc_obj(struct pkvm_mapping,\narch/arm64/kvm/mmu.c-1187-\t\t\t\t\t  GFP_KERNEL_ACCOUNT);\n--\narch/arm64/kvm/mmu.c=2510=int __init kvm_mmu_init(u32 hyp_va_bits)\n--\narch/arm64/kvm/mmu.c-2543-\narch/arm64/kvm/mmu.c:2544:\thyp_pgtable = kzalloc_obj(*hyp_pgtable);\narch/arm64/kvm/mmu.c-2545-\tif (!hyp_pgtable) {\n--\narch/arm64/kvm/nested.c=1328=int kvm_vcpu_allocate_vncr_tlb(struct kvm_vcpu *vcpu)\n--\narch/arm64/kvm/nested.c-1333-\tif (!vcpu-\u003earch.vncr_tlb) {\narch/arm64/kvm/nested.c:1334:\t\tstruct vncr_tlb *vt = kzalloc_obj(*vcpu-\u003earch.vncr_tlb,\narch/arm64/kvm/nested.c-1335-\t\t\t\t\t\t  GFP_KERNEL_ACCOUNT);\n--\narch/arm64/kvm/nested.c=1793=int kvm_init_nv_sysregs(struct kvm_vcpu *vcpu)\n--\narch/arm64/kvm/nested.c-1802-\narch/arm64/kvm/nested.c:1803:\tkvm-\u003earch.sysreg_masks = kzalloc_obj(*(kvm-\u003earch.sysreg_masks),\narch/arm64/kvm/nested.c-1804-\t\t\t\t\t     GFP_KERNEL_ACCOUNT);\n--\narch/arm64/kvm/ptdump.c=116=static struct kvm_ptdump_guest_state *kvm_ptdump_parser_create(struct kvm_s2_mmu *mmu)\n--\narch/arm64/kvm/ptdump.c-121-\narch/arm64/kvm/ptdump.c:122:\tst = kzalloc_obj(struct kvm_ptdump_guest_state, GFP_KERNEL_ACCOUNT);\narch/arm64/kvm/ptdump.c-123-\tif (!st)\n--\narch/arm64/kvm/vgic/vgic-init.c=207=static int kvm_vgic_dist_init(struct kvm *kvm, unsigned int nr_spis)\n--\narch/arm64/kvm/vgic/vgic-init.c-213-\tdist-\u003eactive_spis = (atomic_t)ATOMIC_INIT(0);\narch/arm64/kvm/vgic/vgic-init.c:214:\tdist-\u003espis = kzalloc_objs(struct vgic_irq, nr_spis, GFP_KERNEL_ACCOUNT);\narch/arm64/kvm/vgic/vgic-init.c-215-\tif (!dist-\u003espis)\n--\narch/arm64/kvm/vgic/vgic-init.c=316=static int vgic_allocate_private_irqs_locked(struct kvm_vcpu *vcpu, u32 type)\n--\narch/arm64/kvm/vgic/vgic-init.c-331-\narch/arm64/kvm/vgic/vgic-init.c:332:\tvgic_cpu-\u003eprivate_irqs = kzalloc_objs(struct vgic_irq,\narch/arm64/kvm/vgic/vgic-init.c-333-\t\t\t\t\t      num_private_irqs,\n--\narch/arm64/kvm/vgic/vgic-irqfd.c=142=int kvm_vgic_setup_default_irq_routing(struct kvm *kvm)\n--\narch/arm64/kvm/vgic/vgic-irqfd.c-148-\narch/arm64/kvm/vgic/vgic-irqfd.c:149:\tentries = kzalloc_objs(*entries, nr, GFP_KERNEL_ACCOUNT);\narch/arm64/kvm/vgic/vgic-irqfd.c-150-\tif (!entries)\n--\narch/arm64/kvm/vgic/vgic-its.c=76=static struct vgic_irq *vgic_add_lpi(struct kvm *kvm, u32 intid,\n--\narch/arm64/kvm/vgic/vgic-its.c-87-\narch/arm64/kvm/vgic/vgic-its.c:88:\tirq = kzalloc_obj(struct vgic_irq, GFP_KERNEL_ACCOUNT);\narch/arm64/kvm/vgic/vgic-its.c-89-\tif (!irq)\n--\narch/arm64/kvm/vgic/vgic-its.c=971=static int vgic_its_alloc_collection(struct vgic_its *its,\n--\narch/arm64/kvm/vgic/vgic-its.c-976-\narch/arm64/kvm/vgic/vgic-its.c:977:\tcollection = kzalloc_obj(*collection, GFP_KERNEL_ACCOUNT);\narch/arm64/kvm/vgic/vgic-its.c-978-\tif (!collection)\n--\narch/arm64/kvm/vgic/vgic-its.c=1015=static struct its_ite *vgic_its_alloc_ite(struct its_device *device,\n--\narch/arm64/kvm/vgic/vgic-its.c-1020-\narch/arm64/kvm/vgic/vgic-its.c:1021:\tite = kzalloc_obj(*ite, GFP_KERNEL_ACCOUNT);\narch/arm64/kvm/vgic/vgic-its.c-1022-\tif (!ite)\n--\narch/arm64/kvm/vgic/vgic-its.c=1142=static struct its_device *vgic_its_alloc_device(struct vgic_its *its,\n--\narch/arm64/kvm/vgic/vgic-its.c-1147-\narch/arm64/kvm/vgic/vgic-its.c:1148:\tdevice = kzalloc_obj(*device, GFP_KERNEL_ACCOUNT);\narch/arm64/kvm/vgic/vgic-its.c-1149-\tif (!device)\n--\narch/arm64/kvm/vgic/vgic-its.c=1855=static int vgic_its_create(struct kvm_device *dev, u32 type)\n--\narch/arm64/kvm/vgic/vgic-its.c-1862-\narch/arm64/kvm/vgic/vgic-its.c:1863:\tits = kzalloc_obj(struct vgic_its, GFP_KERNEL_ACCOUNT);\narch/arm64/kvm/vgic/vgic-its.c-1864-\tif (!its)\n--\narch/arm64/kvm/vgic/vgic-mmio-v3.c=886=static int vgic_v3_alloc_redist_region(struct kvm *kvm, uint32_t index,\n--\narch/arm64/kvm/vgic/vgic-mmio-v3.c-931-\narch/arm64/kvm/vgic/vgic-mmio-v3.c:932:\trdreg = kzalloc_obj(*rdreg, GFP_KERNEL_ACCOUNT);\narch/arm64/kvm/vgic/vgic-mmio-v3.c-933-\tif (!rdreg)\n--\narch/arm64/kvm/vgic/vgic-v4.c=242=int vgic_v4_init(struct kvm *kvm)\n--\narch/arm64/kvm/vgic/vgic-v4.c-258-\narch/arm64/kvm/vgic/vgic-v4.c:259:\tdist-\u003eits_vm.vpes = kzalloc_objs(*dist-\u003eits_vm.vpes, nr_vcpus,\narch/arm64/kvm/vgic/vgic-v4.c-260-\t\t\t\t\t GFP_KERNEL_ACCOUNT);\n--\narch/arm64/net/bpf_jit_comp.c=2080=struct bpf_prog *bpf_int_jit_compile(struct bpf_verifier_env *env, struct bpf_prog *prog)\n--\narch/arm64/net/bpf_jit_comp.c-2101-\tif (!jit_data) {\narch/arm64/net/bpf_jit_comp.c:2102:\t\tjit_data = kzalloc_obj(*jit_data);\narch/arm64/net/bpf_jit_comp.c-2103-\t\tif (!jit_data)\n--\narch/csky/kernel/vdso.c=17=static int __init vdso_init(void)\n--\narch/csky/kernel/vdso.c-22-\tvdso_pagelist =\narch/csky/kernel/vdso.c:23:\t\tkzalloc_objs(struct page *, vdso_pages);\narch/csky/kernel/vdso.c-24-\tif (unlikely(vdso_pagelist == NULL)) {\n--\narch/loongarch/kernel/setup.c=466=static int __init add_legacy_isa_io(struct fwnode_handle *fwnode,\n--\narch/loongarch/kernel/setup.c-472-\narch/loongarch/kernel/setup.c:473:\trange = kzalloc_obj(*range, GFP_ATOMIC);\narch/loongarch/kernel/setup.c-474-\tif (!range)\n--\narch/loongarch/kernel/vdso.c=45=static int __init init_vdso(void)\n--\narch/loongarch/kernel/vdso.c-55-\tvdso_info.code_mapping.pages =\narch/loongarch/kernel/vdso.c:56:\t\tkzalloc_objs(struct page *, vdso_info.size / PAGE_SIZE);\narch/loongarch/kernel/vdso.c-57-\n--\narch/loongarch/kvm/intc/eiointc.c=614=static int kvm_eiointc_create(struct kvm_device *dev, u32 type)\n--\narch/loongarch/kvm/intc/eiointc.c-624-\narch/loongarch/kvm/intc/eiointc.c:625:\ts = kzalloc_obj(struct loongarch_eiointc);\narch/loongarch/kvm/intc/eiointc.c-626-\tif (!s)\n--\narch/loongarch/kvm/intc/ipi.c=394=static int kvm_ipi_create(struct kvm_device *dev, u32 type)\n--\narch/loongarch/kvm/intc/ipi.c-411-\narch/loongarch/kvm/intc/ipi.c:412:\ts = kzalloc_obj(struct loongarch_ipi);\narch/loongarch/kvm/intc/ipi.c-413-\tif (!s)\n\n"
}

gemini-3.1-pro-preview

null

null

							input: 18918
							output: 254
							thoughts: 2563
						

**Analysis of the MHI WWAN CTRL DTR/RTS Patch for Uninitialized Memory Exposure**

Okay, so looking at this patch, it seems straightforward enough. My initial concern was about potential uninitialized memory being sent to the device, but after a thorough review, I'm confident that's not the case. Let's break it down:

First, `kzalloc_obj`... yes, that's the macro. A quick review of the definition confirms it zeroes the allocated memory, and that's the key here. We're allocating the `dtr_msg` using `kzalloc_obj(*dtr_msg)`. This ensures everything within `dtr_msg` is initialized to zero before any values are assigned. The code then sets the relevant fields (preamble, ID, size, message) and sends it over the control channel. Crucially, before the data is sent to `mhi_queue_buf`, we have already zero initialized the memory, so no uninitialized memory.

Looking at the receive side in `mhi_wwan_dtr_probe` and later in `mhi_wwan_dtr_dl_xfer_cb`, the buffer `dtr->rx_buf` is used as a DMA sink (`DMA_FROM_DEVICE`). This is also initialized to zero via the `kzalloc_obj(*dtr)` call. This part is receiving data from the device, not sending potentially uninitialized data. So that's safe.

I had to look at `wwan_port_fops_at_ioctl`, but it doesn't do anything that seems wrong.

Also, the `__packed` attribute on `struct mhi_dtr_ctrl_msg` eliminates padding concerns, and even if there were padding, the `kzalloc_obj` would have zeroed it.

The other changes, such as DTR/RTS handling in `wwan_remove_port`, `wwan_port_op_start` and `wwan_port_op_stop` do not send or allocate memory, so they are not important to our discussion.

My initial thought was to double-check `mhi_queue_buf`, but it seems safe because it takes a fully initialized buffer, with its size.

So, in summary: the patch is fine. The code consistently uses `kzalloc_obj` to allocate and zero the memory. There's no scenario where uninitialized memory is read from or exposed. Standard memory safety tools (like KASAN) would be sufficient to catch any other issues (out-of-bounds, use-after-free, etc.). Therefore, we don't need KMSAN specifically for this patch. I can confirm this.

{
  "KMSANReasoning": "The patch introduces a new feature to signal DTR/RTS lines over the IP_CTRL channel in the MHI WWAN CTRL driver. It allocates a new message structure `struct mhi_dtr_ctrl_msg` using `kzalloc_obj`, which guarantees that the allocated memory is fully zero-initialized. The structure is also marked as `__packed`, eliminating any potential padding bytes. The message is then populated with data and sent to the device via `mhi_queue_buf`. Since the memory is fully initialized before being sent, there is no risk of exposing uninitialized memory to the device or userspace. The receive buffer `rx_buf` is used as a sink for `DMA_FROM_DEVICE` and is also part of a zero-initialized structure (`dtr` allocated via `kzalloc_obj`). It does not send uninitialized memory. Any potential memory safety issues, such as out-of-bounds accesses or use-after-free bugs, would be caught by standard KASAN and other bug detectors. Therefore, a dedicated KMSAN fuzzing session is not required.",
  "NeedsKMSAN": false
}

{
  "KMSANReasoning": "The patch introduces a new feature to signal DTR/RTS lines over the IP_CTRL channel in the MHI WWAN CTRL driver. It allocates a new message structure `struct mhi_dtr_ctrl_msg` using `kzalloc_obj`, which guarantees that the allocated memory is fully zero-initialized. The structure is also marked as `__packed`, eliminating any potential padding bytes. The message is then populated with data and sent to the device via `mhi_queue_buf`. Since the memory is fully initialized before being sent, there is no risk of exposing uninitialized memory to the device or userspace. The receive buffer `rx_buf` is used as a sink for `DMA_FROM_DEVICE` and is also part of a zero-initialized structure (`dtr` allocated via `kzalloc_obj`). It does not send uninitialized memory. Any potential memory safety issues, such as out-of-bounds accesses or use-after-free bugs, would be caught by standard KASAN and other bug detectors. Therefore, a dedicated KMSAN fuzzing session is not required.",
  "NeedsKMSAN": false
}