AI Trajectory

null

{
  "EnableConfigs": [
    "SMC"
  ],
  "FocusSymbols": [
    "smc_fback_state_change",
    "smc_fback_data_ready",
    "smc_fback_write_space",
    "smc_fback_error_report",
    "smc_clcsock_data_ready",
    "smc_tcp_syn_recv_sock",
    "smc_hs_congested"
  ],
  "Reasoning": "The patch modifies the behavior of `smc_clcsock_user_data` and `smc_clcsock_user_data_rcu` to return NULL if the `sk_user_data` does not carry the `SK_USER_DATA_NOCOPY` tag alone. This affects the execution flow in multiple SMC callbacks and functions, making it a functional change that should be fuzzed.",
  "WorthFuzzing": true
}

null

{
  "PatchDiff": "commit 78b199dbc1d216a5ac21c361ceb70d9b37c038eb\nAuthor: syz-cluster \u003ctriage@syzkaller.com\u003e\nDate:   Fri Jun 19 15:33:50 2026 +0000\n\n    syz-cluster: applied patch under review\n\ndiff --git a/net/smc/smc.h b/net/smc/smc.h\nindex 52145df83f6e7b..88dfb459b7cc47 100644\n--- a/net/smc/smc.h\n+++ b/net/smc/smc.h\n@@ -342,13 +342,25 @@ static inline void smc_init_saved_callbacks(struct smc_sock *smc)\n \n static inline struct smc_sock *smc_clcsock_user_data(const struct sock *clcsk)\n {\n-\treturn (struct smc_sock *)\n-\t       ((uintptr_t)clcsk-\u003esk_user_data \u0026 ~SK_USER_DATA_NOCOPY);\n+\tuintptr_t data = (uintptr_t)clcsk-\u003esk_user_data;\n+\n+\t/*\n+\t * Return the smc_sock only if the slot carries SMC's tag alone.\n+\t * sockmap stores a sk_psock here tagged SK_USER_DATA_PSOCK; it is\n+\t * not an smc_sock and must not be dereferenced as one.\n+\t */\n+\tif ((data \u0026 ~SK_USER_DATA_PTRMASK) != SK_USER_DATA_NOCOPY)\n+\t\treturn NULL;\n+\treturn (struct smc_sock *)(data \u0026 SK_USER_DATA_PTRMASK);\n }\n \n static inline struct smc_sock *smc_clcsock_user_data_rcu(const struct sock *clcsk)\n {\n-\treturn (struct smc_sock *)rcu_dereference_sk_user_data(clcsk);\n+\tuintptr_t data = (uintptr_t)rcu_dereference(__sk_user_data(clcsk));\n+\n+\tif ((data \u0026 ~SK_USER_DATA_PTRMASK) != SK_USER_DATA_NOCOPY)\n+\t\treturn NULL;\n+\treturn (struct smc_sock *)(data \u0026 SK_USER_DATA_PTRMASK);\n }\n \n /* save target_cb in saved_cb, and replace target_cb with new_cb */\n"
}

gemini-3.1-pro-preview

null

{
  "EnableConfigs": [
    "SMC"
  ],
  "FocusSymbols": [
    "smc_fback_state_change",
    "smc_fback_data_ready",
    "smc_fback_write_space",
    "smc_fback_error_report",
    "smc_clcsock_data_ready",
    "smc_tcp_syn_recv_sock",
    "smc_hs_congested"
  ],
  "Reasoning": "The patch modifies the behavior of `smc_clcsock_user_data` and `smc_clcsock_user_data_rcu` to return NULL if the `sk_user_data` does not carry the `SK_USER_DATA_NOCOPY` tag alone. This affects the execution flow in multiple SMC callbacks and functions, making it a functional change that should be fuzzed.",
  "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 78b199dbc1d216a5ac21c361ceb70d9b37c038eb
Author: syz-cluster <triage@syzkaller.com>
Date:   Fri Jun 19 15:33:50 2026 +0000

    syz-cluster: applied patch under review

diff --git a/net/smc/smc.h b/net/smc/smc.h
index 52145df83f6e7b..88dfb459b7cc47 100644
--- a/net/smc/smc.h
+++ b/net/smc/smc.h
@@ -342,13 +342,25 @@ static inline void smc_init_saved_callbacks(struct smc_sock *smc)
 
 static inline struct smc_sock *smc_clcsock_user_data(const struct sock *clcsk)
 {
-	return (struct smc_sock *)
-	       ((uintptr_t)clcsk->sk_user_data & ~SK_USER_DATA_NOCOPY);
+	uintptr_t data = (uintptr_t)clcsk->sk_user_data;
+
+	/*
+	 * Return the smc_sock only if the slot carries SMC's tag alone.
+	 * sockmap stores a sk_psock here tagged SK_USER_DATA_PSOCK; it is
+	 * not an smc_sock and must not be dereferenced as one.
+	 */
+	if ((data & ~SK_USER_DATA_PTRMASK) != SK_USER_DATA_NOCOPY)
+		return NULL;
+	return (struct smc_sock *)(data & SK_USER_DATA_PTRMASK);
 }
 
 static inline struct smc_sock *smc_clcsock_user_data_rcu(const struct sock *clcsk)
 {
-	return (struct smc_sock *)rcu_dereference_sk_user_data(clcsk);
+	uintptr_t data = (uintptr_t)rcu_dereference(__sk_user_data(clcsk));
+
+	if ((data & ~SK_USER_DATA_PTRMASK) != SK_USER_DATA_NOCOPY)
+		return NULL;
+	return (struct smc_sock *)(data & SK_USER_DATA_PTRMASK);
 }
 
 /* save target_cb in saved_cb, and replace target_cb with new_cb */

gemini-3.1-pro-preview

null

null

							input: 2155
							output: 24
							thoughts: 107
						

**Analyzing SMC Networking Subsystem Modifications**

Okay, so this patch is clearly digging into the `net/smc/smc.h` file and zeroing in on `smc_clcsock_user_data` and `smc_clcsock_user_data_rcu`. The core of the change seems to be around how we handle `sk_user_data`. It's checking for that `SK_USER_DATA_NOCOPY` tag – specifically, if *only* that tag is set. If anything else is tagged along with it, the function immediately bails out and returns `NULL`. This is a pretty focused functional alteration within the SMC subsystem. My immediate question is, where are these functions *actually* being used? Understanding the context of the calls is crucial to understanding the impact of this change. Let's trace those calls.

{
  "Expression": "smc_clcsock_user_data"
}

{
  "Output": "net/smc/af_smc.c=122=static struct sock *smc_tcp_syn_recv_sock(const struct sock *sk,\n--\nnet/smc/af_smc.c-134-\trcu_read_lock();\nnet/smc/af_smc.c:135:\tsmc = smc_clcsock_user_data_rcu(sk);\nnet/smc/af_smc.c-136-\tif (!smc || !refcount_inc_not_zero(\u0026smc-\u003esk.sk_refcnt)) {\n--\nnet/smc/af_smc.c=174=static bool smc_hs_congested(const struct sock *sk)\n--\nnet/smc/af_smc.c-177-\nnet/smc/af_smc.c:178:\tsmc = smc_clcsock_user_data(sk);\nnet/smc/af_smc.c-179-\n--\nnet/smc/af_smc.c=864=static void smc_fback_state_change(struct sock *clcsk)\n--\nnet/smc/af_smc.c-868-\tread_lock_bh(\u0026clcsk-\u003esk_callback_lock);\nnet/smc/af_smc.c:869:\tsmc = smc_clcsock_user_data(clcsk);\nnet/smc/af_smc.c-870-\tif (smc)\n--\nnet/smc/af_smc.c=876=static void smc_fback_data_ready(struct sock *clcsk)\n--\nnet/smc/af_smc.c-880-\tread_lock_bh(\u0026clcsk-\u003esk_callback_lock);\nnet/smc/af_smc.c:881:\tsmc = smc_clcsock_user_data(clcsk);\nnet/smc/af_smc.c-882-\tif (smc)\n--\nnet/smc/af_smc.c=888=static void smc_fback_write_space(struct sock *clcsk)\n--\nnet/smc/af_smc.c-892-\tread_lock_bh(\u0026clcsk-\u003esk_callback_lock);\nnet/smc/af_smc.c:893:\tsmc = smc_clcsock_user_data(clcsk);\nnet/smc/af_smc.c-894-\tif (smc)\n--\nnet/smc/af_smc.c=900=static void smc_fback_error_report(struct sock *clcsk)\n--\nnet/smc/af_smc.c-904-\tread_lock_bh(\u0026clcsk-\u003esk_callback_lock);\nnet/smc/af_smc.c:905:\tsmc = smc_clcsock_user_data(clcsk);\nnet/smc/af_smc.c-906-\tif (smc)\n--\nnet/smc/af_smc.c=2629=static void smc_clcsock_data_ready(struct sock *listen_clcsock)\n--\nnet/smc/af_smc.c-2633-\tread_lock_bh(\u0026listen_clcsock-\u003esk_callback_lock);\nnet/smc/af_smc.c:2634:\tlsmc = smc_clcsock_user_data(listen_clcsock);\nnet/smc/af_smc.c-2635-\tif (!lsmc)\n--\nnet/smc/smc.h=335=static inline void smc_init_saved_callbacks(struct smc_sock *smc)\n--\nnet/smc/smc.h-342-\nnet/smc/smc.h:343:static inline struct smc_sock *smc_clcsock_user_data(const struct sock *clcsk)\nnet/smc/smc.h-344-{\n--\nnet/smc/smc.h-356-\nnet/smc/smc.h:357:static inline struct smc_sock *smc_clcsock_user_data_rcu(const struct sock *clcsk)\nnet/smc/smc.h-358-{\n"
}

gemini-3.1-pro-preview

null

null

							input: 3600
							output: 16
							thoughts: 220
						

**Analyzing SMC Net Functions for Fuzzing Potential**

Okay, so I'm looking at these functions within `net/smc/af_smc.c`. Specifically, I'm thinking about the callbacks: `smc_fback_state_change`, `smc_fback_data_ready`, `smc_fback_write_space`, `smc_fback_error_report`, `smc_clcsock_data_ready`, `smc_tcp_syn_recv_sock`, and `smc_hs_congested`. These look like functional changes that could be interesting to explore for fuzzing. Given that, I should mark this as `WorthFuzzing=true`.

For focus symbols, I'll definitely keep those function names in mind. They're the core of where the interesting behavior is happening.

Before I go further, I should probably take a quick look at `net/smc/Kconfig`. I need to understand what configuration options might impact these functions. Understanding the dependencies will help me figure out the best way to approach a fuzzing campaign.

{
  "Expression": "config SMC"
}

{
  "Output": "arch/powerpc/platforms/8xx/Kconfig=146=config I2C_SPI_SMC1_UCODE_PATCH\n--\narch/powerpc/platforms/8xx/Kconfig-150-\narch/powerpc/platforms/8xx/Kconfig:151:config SMC_UCODE_PATCH\narch/powerpc/platforms/8xx/Kconfig-152-\tbool \"SMC relocation patch\"\n--\ndrivers/net/ethernet/smsc/Kconfig=20=if NET_VENDOR_SMSC\ndrivers/net/ethernet/smsc/Kconfig-21-\ndrivers/net/ethernet/smsc/Kconfig:22:config SMC91X\ndrivers/net/ethernet/smsc/Kconfig-23-\ttristate \"SMC 91C9x/91C1xxx support\"\n--\nnet/smc/Kconfig-1-# SPDX-License-Identifier: GPL-2.0-only\nnet/smc/Kconfig:2:config SMC\nnet/smc/Kconfig-3-\ttristate \"SMC socket protocol family\"\n--\nnet/smc/Kconfig-13-\nnet/smc/Kconfig:14:config SMC_DIAG\nnet/smc/Kconfig-15-\ttristate \"SMC: socket monitoring interface\"\n--\nnet/smc/Kconfig-22-\nnet/smc/Kconfig:23:config SMC_HS_CTRL_BPF\nnet/smc/Kconfig-24-\tbool \"Generic eBPF hook for SMC handshake flow\"\n"
}

gemini-3.1-pro-preview

null

null

							input: 4470
							output: 33
							thoughts: 24
						

Here's my summary, as the expert:

**Investigating the SMC Configuration**

Okay, so the current configuration is `SMC`. That's my starting point. Now, to understand how this `SMC` option is put together, I need to dig into its dependencies. My first stop is always the `net/smc/Kconfig` file. That's where all the configuration options related to SMC, and how they relate to other parts of the network stack, are defined. Time to see what's what in there.

{
  "File": "net/smc/Kconfig",
  "FirstLine": 1,
  "LineCount": 20
}

{
  "Contents": "   1:\t# SPDX-License-Identifier: GPL-2.0-only\n   2:\tconfig SMC\n   3:\t\ttristate \"SMC socket protocol family\"\n   4:\t\tdepends on INET \u0026\u0026 INFINIBAND \u0026\u0026 DIBS\n   5:\t\thelp\n   6:\t\t  SMC-R provides a \"sockets over RDMA\" solution making use of\n   7:\t\t  RDMA over Converged Ethernet (RoCE) technology to upgrade\n   8:\t\t  AF_INET TCP connections transparently.\n   9:\t\t  The Linux implementation of the SMC-R solution is designed as\n  10:\t\t  a separate socket family SMC.\n  11:\t\n  12:\t\t  Select this option if you want to run SMC socket applications\n  13:\t\n  14:\tconfig SMC_DIAG\n  15:\t\ttristate \"SMC: socket monitoring interface\"\n  16:\t\tdepends on SMC\n  17:\t\thelp\n  18:\t\t  Support for SMC socket monitoring interface used by tools such as\n  19:\t\t  smcss.\n  20:\t\n"
}

gemini-3.1-pro-preview

null

null

							input: 4912
							output: 206
							thoughts: 62911
						

{
  "EnableConfigs": [
    "SMC"
  ],
  "FocusSymbols": [
    "smc_fback_state_change",
    "smc_fback_data_ready",
    "smc_fback_write_space",
    "smc_fback_error_report",
    "smc_clcsock_data_ready",
    "smc_tcp_syn_recv_sock",
    "smc_hs_congested"
  ],
  "Reasoning": "The patch modifies the behavior of `smc_clcsock_user_data` and `smc_clcsock_user_data_rcu` to return NULL if the `sk_user_data` does not carry the `SK_USER_DATA_NOCOPY` tag alone. This affects the execution flow in multiple SMC callbacks and functions, making it a functional change that should be fuzzed.",
  "WorthFuzzing": true
}

{
  "EnableConfigs": [
    "SMC"
  ],
  "FocusSymbols": [
    "smc_fback_state_change",
    "smc_fback_data_ready",
    "smc_fback_write_space",
    "smc_fback_error_report",
    "smc_clcsock_data_ready",
    "smc_tcp_syn_recv_sock",
    "smc_hs_congested"
  ],
  "Reasoning": "The patch modifies the behavior of `smc_clcsock_user_data` and `smc_clcsock_user_data_rcu` to return NULL if the `sk_user_data` does not carry the `SK_USER_DATA_NOCOPY` tag alone. This affects the execution flow in multiple SMC callbacks and functions, making it a functional change that should be fuzzed.",
  "WorthFuzzing": true
}