AI Trajectory

null

{
  "EnableConfigs": [
    "VSOCKETS",
    "VSOCKETS_LOOPBACK",
    "VIRTIO_VSOCKETS",
    "VHOST_VSOCK"
  ],
  "FocusSymbols": [
    "virtio_transport_send_pkt_info"
  ],
  "Reasoning": "The patch modifies virtio_transport_send_pkt_info to correctly restore the iov_iter state if packet allocation or transmission fails. This is a functional change in the virtio vsock transport that handles error paths during data transmission, which should be fuzzed to ensure no iterator state corruption occurs.",
  "WorthFuzzing": true
}

null

{
  "PatchDiff": "commit 404fd69f99a3f14e15332b395871c11bd2ed292f\nAuthor: syz-cluster \u003ctriage@syzkaller.com\u003e\nDate:   Mon Jun 22 22:44:54 2026 +0000\n\n    syz-cluster: applied patch under review\n\ndiff --git a/lib/iov_iter.c b/lib/iov_iter.c\nindex 273919b1616176..f5df63961fb24f 100644\n--- a/lib/iov_iter.c\n+++ b/lib/iov_iter.c\n@@ -1491,6 +1491,7 @@ void iov_iter_restore(struct iov_iter *i, struct iov_iter_state *state)\n \t\ti-\u003e__iov -= state-\u003enr_segs - i-\u003enr_segs;\n \ti-\u003enr_segs = state-\u003enr_segs;\n }\n+EXPORT_SYMBOL_GPL(iov_iter_restore);\n \n /*\n  * Extract a list of contiguous pages from an ITER_FOLIOQ iterator.  This does\ndiff --git a/net/vmw_vsock/virtio_transport_common.c b/net/vmw_vsock/virtio_transport_common.c\nindex 09475007165b36..35fd4094d771d8 100644\n--- a/net/vmw_vsock/virtio_transport_common.c\n+++ b/net/vmw_vsock/virtio_transport_common.c\n@@ -295,6 +295,7 @@ static int virtio_transport_send_pkt_info(struct vsock_sock *vsk,\n \tu32 max_skb_len = VIRTIO_VSOCK_MAX_PKT_BUF_SIZE;\n \tu32 src_cid, src_port, dst_cid, dst_port;\n \tconst struct virtio_transport *t_ops;\n+\tstruct iov_iter_state msg_iter_state;\n \tstruct virtio_vsock_sock *vvs;\n \tstruct ubuf_info *uarg = NULL;\n \tu32 pkt_len = info-\u003epkt_len;\n@@ -368,8 +369,17 @@ static int virtio_transport_send_pkt_info(struct vsock_sock *vsk,\n \t\tstruct sk_buff *skb;\n \t\tsize_t skb_len;\n \n+\t\t/* Save iterator state in case allocation or transmission fails\n+\t\t * so we can restore it and retry.\n+\t\t */\n+\t\tif (info-\u003emsg)\n+\t\t\tiov_iter_save_state(\u0026info-\u003emsg-\u003emsg_iter, \u0026msg_iter_state);\n+\n \t\tskb_len = min(max_skb_len, rest_len);\n \n+\t\t/* Note: virtio_transport_alloc_skb() can advance info-\u003emsg-\u003emsg_iter\n+\t\t * even if it fails (e.g. partial GUP success).\n+\t\t */\n \t\tskb = virtio_transport_alloc_skb(info, skb_len, can_zcopy,\n \t\t\t\t\t\t uarg,\n \t\t\t\t\t\t src_cid, src_port,\n@@ -399,6 +409,9 @@ static int virtio_transport_send_pkt_info(struct vsock_sock *vsk,\n \t\t\tbreak;\n \t} while (rest_len);\n \n+\tif (info-\u003emsg \u0026\u0026 ret \u003c 0)\n+\t\tiov_iter_restore(\u0026info-\u003emsg-\u003emsg_iter, \u0026msg_iter_state);\n+\n \tvirtio_transport_put_credit(vvs, rest_len);\n \n \t/* msg_zerocopy_realloc() initializes the ubuf_info refcnt to 1.\n"
}

gemini-3.1-pro-preview

null

{
  "EnableConfigs": [
    "VSOCKETS",
    "VSOCKETS_LOOPBACK",
    "VIRTIO_VSOCKETS",
    "VHOST_VSOCK"
  ],
  "FocusSymbols": [
    "virtio_transport_send_pkt_info"
  ],
  "Reasoning": "The patch modifies virtio_transport_send_pkt_info to correctly restore the iov_iter state if packet allocation or transmission fails. This is a functional change in the virtio vsock transport that handles error paths during data transmission, which should be fuzzed to ensure no iterator state corruption occurs.",
  "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).

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.
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.
   Do not list too generic configs (we already have them enabled). Only list those that
   specifically cover the modified code. 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 404fd69f99a3f14e15332b395871c11bd2ed292f
Author: syz-cluster <triage@syzkaller.com>
Date:   Mon Jun 22 22:44:54 2026 +0000

    syz-cluster: applied patch under review

diff --git a/lib/iov_iter.c b/lib/iov_iter.c
index 273919b1616176..f5df63961fb24f 100644
--- a/lib/iov_iter.c
+++ b/lib/iov_iter.c
@@ -1491,6 +1491,7 @@ void iov_iter_restore(struct iov_iter *i, struct iov_iter_state *state)
 		i->__iov -= state->nr_segs - i->nr_segs;
 	i->nr_segs = state->nr_segs;
 }
+EXPORT_SYMBOL_GPL(iov_iter_restore);
 
 /*
  * Extract a list of contiguous pages from an ITER_FOLIOQ iterator.  This does
diff --git a/net/vmw_vsock/virtio_transport_common.c b/net/vmw_vsock/virtio_transport_common.c
index 09475007165b36..35fd4094d771d8 100644
--- a/net/vmw_vsock/virtio_transport_common.c
+++ b/net/vmw_vsock/virtio_transport_common.c
@@ -295,6 +295,7 @@ static int virtio_transport_send_pkt_info(struct vsock_sock *vsk,
 	u32 max_skb_len = VIRTIO_VSOCK_MAX_PKT_BUF_SIZE;
 	u32 src_cid, src_port, dst_cid, dst_port;
 	const struct virtio_transport *t_ops;
+	struct iov_iter_state msg_iter_state;
 	struct virtio_vsock_sock *vvs;
 	struct ubuf_info *uarg = NULL;
 	u32 pkt_len = info->pkt_len;
@@ -368,8 +369,17 @@ static int virtio_transport_send_pkt_info(struct vsock_sock *vsk,
 		struct sk_buff *skb;
 		size_t skb_len;
 
+		/* Save iterator state in case allocation or transmission fails
+		 * so we can restore it and retry.
+		 */
+		if (info->msg)
+			iov_iter_save_state(&info->msg->msg_iter, &msg_iter_state);
+
 		skb_len = min(max_skb_len, rest_len);
 
+		/* Note: virtio_transport_alloc_skb() can advance info->msg->msg_iter
+		 * even if it fails (e.g. partial GUP success).
+		 */
 		skb = virtio_transport_alloc_skb(info, skb_len, can_zcopy,
 						 uarg,
 						 src_cid, src_port,
@@ -399,6 +409,9 @@ static int virtio_transport_send_pkt_info(struct vsock_sock *vsk,
 			break;
 	} while (rest_len);
 
+	if (info->msg && ret < 0)
+		iov_iter_restore(&info->msg->msg_iter, &msg_iter_state);
+
 	virtio_transport_put_credit(vvs, rest_len);
 
 	/* msg_zerocopy_realloc() initializes the ubuf_info refcnt to 1.

gemini-3.1-pro-preview

null

null

							input: 2493
							output: 37
							thoughts: 273
						

**Analyzing a vsock Patch**

Okay, so I've got this patch affecting `lib/iov_iter.c` and `net/vmw_vsock/virtio_transport_common.c`. It looks like they're exporting `iov_iter_restore` and leveraging it within `virtio_transport_send_pkt_info`. The goal is to restore the `msg_iter` state if something goes sideways during packet allocation or transmission. This is definitely a functional change in the virtio vsock transport.

Let's quickly verify the modified functions: `iov_iter_restore` is being exported, and the critical change is within `virtio_transport_send_pkt_info`. Ah, got it. They're saving the iterator state *before* the `virtio_transport_alloc_skb` call and restoring it if `ret` is less than zero. Smart, keeping that iterator state consistent.

Now, the important question: fuzzability. Given that this is a functional change within vsock, the answer is a resounding "yes". We need to be thorough.

Right, so to make sure we set up the right config options, I need to know the necessary components. Let's see what we are dealing with. I need to confirm the dependencies in `net/vmw_vsock/virtio_transport_common.c`. It looks like we need to include both `VSOCKETS` and `VIRTIO_VSOCKETS_COMMON`. Okay, and now I just need to verify that `virtio_transport_common.o` is being included. I'll just grep for it in the `net/vmw_vsock/Makefile` to make sure. That should be enough to get the right config for fuzzing.

{
  "Expression": "virtio_transport_common.o",
  "PathPrefix": "net/vmw_vsock/Makefile"
}

{
  "Output": "net/vmw_vsock/Makefile=5=obj-$(CONFIG_VIRTIO_VSOCKETS) += vmw_vsock_virtio_transport.o\nnet/vmw_vsock/Makefile:6:obj-$(CONFIG_VIRTIO_VSOCKETS_COMMON) += vmw_vsock_virtio_transport_common.o\nnet/vmw_vsock/Makefile-7-obj-$(CONFIG_HYPERV_VSOCKETS) += hv_sock.o\n--\nnet/vmw_vsock/Makefile=18=vmw_vsock_virtio_transport-y += virtio_transport.o\nnet/vmw_vsock/Makefile-19-\nnet/vmw_vsock/Makefile:20:vmw_vsock_virtio_transport_common-y += virtio_transport_common.o\nnet/vmw_vsock/Makefile-21-\n"
}

gemini-3.1-pro-preview

null

null

							input: 3408
							output: 40
							thoughts: 79
						

Okay, let's break this down.

**Investigating the `VIRTIO_VSOCKETS_COMMON` Configuration**

Right, so I see `CONFIG_VIRTIO_VSOCKETS_COMMON`. But hang on, isn't `VIRTIO_VSOCKETS_COMMON` typically pulled in by something else? Usually, it's either `VIRTIO_VSOCKETS` itself, or perhaps `VHOST_VSOCK`, or even `VSOCKETS_LOOPBACK`. These are the typical dependencies in the ecosystem. I need to understand the connection.

Given the context, I think the next logical step would be to examine the Kconfig file related to this module. I'll need to go and check `net/vmw_vsock/Kconfig` to see the dependencies and relationships, and exactly which config options trigger its inclusion. This will give me a clear picture of how this component fits into the larger architecture and where its inclusion is controlled. That Kconfig file should illuminate the specific circumstances where `VIRTIO_VSOCKETS_COMMON` is automatically selected.

{
  "Expression": "config VIRTIO_VSOCKETS_COMMON",
  "PathPrefix": "net/vmw_vsock/Kconfig"
}

{
  "Output": "net/vmw_vsock/Kconfig=53=config VIRTIO_VSOCKETS\n--\nnet/vmw_vsock/Kconfig-65-\nnet/vmw_vsock/Kconfig:66:config VIRTIO_VSOCKETS_COMMON\nnet/vmw_vsock/Kconfig-67-\ttristate\n"
}

gemini-3.1-pro-preview

null

null

							input: 3855
							output: 40
							thoughts: 8
						

Okay, here's the summary, expressed in the first person, assuming I'm an expert in whatever field is relevant:

**Deconstructing the Selection Mechanism**

Alright, time to dive in. My first instinct, as always, is to understand the "why" behind this selection. Instead of jumping to conclusions or potential solutions, let's start with the fundamental question: what *exactly* is responsible for making this selection? It's crucial to break down the process step-by-step. Let's trace it back, consider all contributing factors, and identify the root cause. A methodical approach, always.

{
  "Expression": "select VIRTIO_VSOCKETS_COMMON",
  "PathPrefix": "net/vmw_vsock/Kconfig"
}

{
  "Output": "net/vmw_vsock/Kconfig=29=config VSOCKETS_LOOPBACK\n--\nnet/vmw_vsock/Kconfig-32-\tdefault y\nnet/vmw_vsock/Kconfig:33:\tselect VIRTIO_VSOCKETS_COMMON\nnet/vmw_vsock/Kconfig-34-\thelp\n--\nnet/vmw_vsock/Kconfig=53=config VIRTIO_VSOCKETS\n--\nnet/vmw_vsock/Kconfig-55-\tdepends on VSOCKETS \u0026\u0026 VIRTIO\nnet/vmw_vsock/Kconfig:56:\tselect VIRTIO_VSOCKETS_COMMON\nnet/vmw_vsock/Kconfig-57-\thelp\n"
}

gemini-3.1-pro-preview

null

null

							input: 4224
							output: 37
							thoughts: 19
						

Here's a first-person summary, tailored for an expert audience, based on the provided text:

**Digging into VHOST_VSOCK Configuration**

Okay, so we need to make sure we've covered all the bases regarding VHOST_VSOCK. My immediate thought is, "Have we properly configured this thing?" The first place my mental checklist goes is the `drivers/vhost/Kconfig` file. That's the standard location for kernel configuration options related to vhost drivers, and it's almost certain that's where the relevant `VHOST_VSOCK` option lives. I'm going to quickly scan that file to confirm its presence and check its dependencies and default settings. It's crucial to ensure that the Kconfig properly exposes the feature and that we're dealing with the correct config option. Once I confirm, I can then drill down into any potential interactions or dependencies it might have with other components.

{
  "Expression": "select VIRTIO_VSOCKETS_COMMON",
  "PathPrefix": "drivers/vhost/Kconfig"
}

{
  "Output": "drivers/vhost/Kconfig=56=config VHOST_VSOCK\n--\ndrivers/vhost/Kconfig-59-\tselect VHOST\ndrivers/vhost/Kconfig:60:\tselect VIRTIO_VSOCKETS_COMMON\ndrivers/vhost/Kconfig-61-\tdefault n\n"
}

gemini-3.1-pro-preview

null

null

							input: 4563
							output: 46
							thoughts: 215
						

**VSOCK Kernel Module Configuration and Fuzzing Strategy**

Okay, so I'm thinking about VSOCK configurations for fuzzing. I should enable `VSOCKETS`, `VIRTIO_VSOCKETS`, `VHOST_VSOCK`, and `VSOCKETS_LOOPBACK`. `VSOCKETS_LOOPBACK` is likely the simplest to start with because it doesn't need any virtio devices, making setup much easier for fuzzing. To make sure I have all the config symbols straight, I'll list them out: `VSOCKETS`, `VSOCKETS_LOOPBACK`, `VIRTIO_VSOCKETS`, and `VHOST_VSOCK`.

Now, the important function to focus on is `virtio_transport_send_pkt_info`. The patch focuses on a bug in that function where the `msg_iter` state isn't restored correctly if an error occurs during packet allocation or transmission. This is a crucial functional change within the virtio vsock transport. Therefore, I need to fuzz `virtio_transport_send_pkt_info` thoroughly to ensure that the iterator state is restored and there are no use-after-free or other memory corruption issues. It's a key area to test for stability.

Just to be absolutely certain, I'll double check the code around `virtio_transport_send_pkt_info` to refresh my understanding.

{
  "Expression": "virtio_transport_send_pkt_info",
  "PathPrefix": "net/vmw_vsock/virtio_transport_common.c"
}

{
  "Output": "net/vmw_vsock/virtio_transport_common.c=205=static struct sk_buff *virtio_transport_alloc_skb(struct virtio_vsock_pkt_info *info,\n--\nnet/vmw_vsock/virtio_transport_common.c-291- */\nnet/vmw_vsock/virtio_transport_common.c:292:static int virtio_transport_send_pkt_info(struct vsock_sock *vsk,\nnet/vmw_vsock/virtio_transport_common.c-293-\t\t\t\t\t  struct virtio_vsock_pkt_info *info)\n--\nnet/vmw_vsock/virtio_transport_common.c=525=static int virtio_transport_send_credit_update(struct vsock_sock *vsk)\n--\nnet/vmw_vsock/virtio_transport_common.c-532-\nnet/vmw_vsock/virtio_transport_common.c:533:\treturn virtio_transport_send_pkt_info(vsk, \u0026info);\nnet/vmw_vsock/virtio_transport_common.c-534-}\n--\nnet/vmw_vsock/virtio_transport_common.c=1072=int virtio_transport_connect(struct vsock_sock *vsk)\n--\nnet/vmw_vsock/virtio_transport_common.c-1079-\nnet/vmw_vsock/virtio_transport_common.c:1080:\treturn virtio_transport_send_pkt_info(vsk, \u0026info);\nnet/vmw_vsock/virtio_transport_common.c-1081-}\n--\nnet/vmw_vsock/virtio_transport_common.c=1084=int virtio_transport_shutdown(struct vsock_sock *vsk, int mode)\n--\nnet/vmw_vsock/virtio_transport_common.c-1095-\nnet/vmw_vsock/virtio_transport_common.c:1096:\treturn virtio_transport_send_pkt_info(vsk, \u0026info);\nnet/vmw_vsock/virtio_transport_common.c-1097-}\n--\nnet/vmw_vsock/virtio_transport_common.c=1111=virtio_transport_stream_enqueue(struct vsock_sock *vsk,\n--\nnet/vmw_vsock/virtio_transport_common.c-1122-\nnet/vmw_vsock/virtio_transport_common.c:1123:\treturn virtio_transport_send_pkt_info(vsk, \u0026info);\nnet/vmw_vsock/virtio_transport_common.c-1124-}\n--\nnet/vmw_vsock/virtio_transport_common.c=1151=static int virtio_transport_reset(struct vsock_sock *vsk,\n--\nnet/vmw_vsock/virtio_transport_common.c-1164-\nnet/vmw_vsock/virtio_transport_common.c:1165:\treturn virtio_transport_send_pkt_info(vsk, \u0026info);\nnet/vmw_vsock/virtio_transport_common.c-1166-}\n--\nnet/vmw_vsock/virtio_transport_common.c=1175=static int virtio_transport_reset_no_sock(const struct virtio_transport *t,\n--\nnet/vmw_vsock/virtio_transport_common.c-1191-\t\t * t-\u003esend_pkt(), instead of relying on\nnet/vmw_vsock/virtio_transport_common.c:1192:\t\t * virtio_transport_send_pkt_info() to pass it. It is not needed\nnet/vmw_vsock/virtio_transport_common.c-1193-\t\t * by virtio_transport_alloc_skb().\n--\nnet/vmw_vsock/virtio_transport_common.c=1501=virtio_transport_send_response(struct vsock_sock *vsk,\n--\nnet/vmw_vsock/virtio_transport_common.c-1513-\nnet/vmw_vsock/virtio_transport_common.c:1514:\treturn virtio_transport_send_pkt_info(vsk, \u0026info);\nnet/vmw_vsock/virtio_transport_common.c-1515-}\n"
}

gemini-3.1-pro-preview

null

null

							input: 6253
							output: 138
							thoughts: 113
						

**Analyzing the virtio Packet Transmission Path**

Okay, so I'm looking at `virtio_transport_send_pkt_info`. It seems this function is pretty central, reachable from a bunch of different spots in the code, like `virtio_transport_stream_enqueue`, which is used when we're sending data over vsock. It looks like a good place to start my investigation.

I considered whether `iov_iter_restore` might be a relevant focus point. However, that's a pretty generic function in `lib/iov_iter.c`. It's used everywhere, so I don't think it'll provide the specific insights I need right now. `virtio_transport_send_pkt_info` seems much more promising.

Alright, I'm going to set some breakpoints and let's get some results back.

{
  "EnableConfigs": [
    "VSOCKETS",
    "VSOCKETS_LOOPBACK",
    "VIRTIO_VSOCKETS",
    "VHOST_VSOCK"
  ],
  "FocusSymbols": [
    "virtio_transport_send_pkt_info"
  ],
  "Reasoning": "The patch modifies virtio_transport_send_pkt_info to correctly restore the iov_iter state if packet allocation or transmission fails. This is a functional change in the virtio vsock transport that handles error paths during data transmission, which should be fuzzed to ensure no iterator state corruption occurs.",
  "WorthFuzzing": true
}

{
  "EnableConfigs": [
    "VSOCKETS",
    "VSOCKETS_LOOPBACK",
    "VIRTIO_VSOCKETS",
    "VHOST_VSOCK"
  ],
  "FocusSymbols": [
    "virtio_transport_send_pkt_info"
  ],
  "Reasoning": "The patch modifies virtio_transport_send_pkt_info to correctly restore the iov_iter state if packet allocation or transmission fails. This is a functional change in the virtio vsock transport that handles error paths during data transmission, which should be fuzzed to ensure no iterator state corruption occurs.",
  "WorthFuzzing": true
}