AI Trajectory

null

{
  "EnableConfigs": [
    "SMC"
  ],
  "FocusSymbols": [
    "smc_tcp_syn_recv_sock",
    "smc_clcsock_accept"
  ],
  "Reasoning": "The patch modifies the socket accept and syn receive paths in the SMC protocol to prevent sockmap from claiming the sk_user_data slot. This is a functional change in the core SMC protocol logic.",
  "WorthFuzzing": true
}

null

{
  "PatchDiff": "commit d470338666ae7cafb9529243dc2f8f83d15e2431\nAuthor: syz-cluster \u003ctriage@syzkaller.com\u003e\nDate:   Mon Jun 29 10:17:19 2026 +0000\n\n    syz-cluster: applied patch under review\n\ndiff --git a/net/smc/af_smc.c b/net/smc/af_smc.c\nindex b5db69073e20fc..78f162344fe3ae 100644\n--- a/net/smc/af_smc.c\n+++ b/net/smc/af_smc.c\n@@ -154,7 +154,11 @@ static struct sock *smc_tcp_syn_recv_sock(const struct sock *sk,\n \t\t\t\t\t       own_req, opt_child_init);\n \t/* child must not inherit smc or its ops */\n \tif (child) {\n-\t\trcu_assign_sk_user_data(child, NULL);\n+\t\t/* reserve sk_user_data so sockmap cannot claim the slot */\n+\t\twrite_lock_bh(\u0026child-\u003esk_callback_lock);\n+\t\t__rcu_assign_sk_user_data_with_flags(child, NULL,\n+\t\t\t\t\t\t     SK_USER_DATA_NOCOPY);\n+\t\twrite_unlock_bh(\u0026child-\u003esk_callback_lock);\n \n \t\t/* v4-mapped sockets don't inherit parent ops. Don't restore. */\n \t\tif (inet_csk(child)-\u003eicsk_af_ops == inet_csk(sk)-\u003eicsk_af_ops)\n@@ -1773,6 +1777,7 @@ static int smc_clcsock_accept(struct smc_sock *lsmc, struct smc_sock **new_smc)\n \t/* new clcsock has inherited the smc listen-specific sk_data_ready\n \t * function; switch it back to the original sk_data_ready function\n \t */\n+\twrite_lock_bh(\u0026new_clcsock-\u003esk-\u003esk_callback_lock);\n \tnew_clcsock-\u003esk-\u003esk_data_ready = lsmc-\u003eclcsk_data_ready;\n \n \t/* if new clcsock has also inherited the fallback-specific callback\n@@ -1786,6 +1791,9 @@ static int smc_clcsock_accept(struct smc_sock *lsmc, struct smc_sock **new_smc)\n \t\tif (lsmc-\u003eclcsk_error_report)\n \t\t\tnew_clcsock-\u003esk-\u003esk_error_report = lsmc-\u003eclcsk_error_report;\n \t}\n+\t/* release the slot reserved in smc_tcp_syn_recv_sock() */\n+\trcu_assign_sk_user_data(new_clcsock-\u003esk, NULL);\n+\twrite_unlock_bh(\u0026new_clcsock-\u003esk-\u003esk_callback_lock);\n \n \t(*new_smc)-\u003eclcsock = new_clcsock;\n out:\n"
}

gemini-3.1-pro-preview

null

{
  "EnableConfigs": [
    "SMC"
  ],
  "FocusSymbols": [
    "smc_tcp_syn_recv_sock",
    "smc_clcsock_accept"
  ],
  "Reasoning": "The patch modifies the socket accept and syn receive paths in the SMC protocol to prevent sockmap from claiming the sk_user_data slot. This is a functional change in the core SMC protocol logic.",
  "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 d470338666ae7cafb9529243dc2f8f83d15e2431
Author: syz-cluster <triage@syzkaller.com>
Date:   Mon Jun 29 10:17:19 2026 +0000

    syz-cluster: applied patch under review

diff --git a/net/smc/af_smc.c b/net/smc/af_smc.c
index b5db69073e20fc..78f162344fe3ae 100644
--- a/net/smc/af_smc.c
+++ b/net/smc/af_smc.c
@@ -154,7 +154,11 @@ static struct sock *smc_tcp_syn_recv_sock(const struct sock *sk,
 					       own_req, opt_child_init);
 	/* child must not inherit smc or its ops */
 	if (child) {
-		rcu_assign_sk_user_data(child, NULL);
+		/* reserve sk_user_data so sockmap cannot claim the slot */
+		write_lock_bh(&child->sk_callback_lock);
+		__rcu_assign_sk_user_data_with_flags(child, NULL,
+						     SK_USER_DATA_NOCOPY);
+		write_unlock_bh(&child->sk_callback_lock);
 
 		/* v4-mapped sockets don't inherit parent ops. Don't restore. */
 		if (inet_csk(child)->icsk_af_ops == inet_csk(sk)->icsk_af_ops)
@@ -1773,6 +1777,7 @@ static int smc_clcsock_accept(struct smc_sock *lsmc, struct smc_sock **new_smc)
 	/* new clcsock has inherited the smc listen-specific sk_data_ready
 	 * function; switch it back to the original sk_data_ready function
 	 */
+	write_lock_bh(&new_clcsock->sk->sk_callback_lock);
 	new_clcsock->sk->sk_data_ready = lsmc->clcsk_data_ready;
 
 	/* if new clcsock has also inherited the fallback-specific callback
@@ -1786,6 +1791,9 @@ static int smc_clcsock_accept(struct smc_sock *lsmc, struct smc_sock **new_smc)
 		if (lsmc->clcsk_error_report)
 			new_clcsock->sk->sk_error_report = lsmc->clcsk_error_report;
 	}
+	/* release the slot reserved in smc_tcp_syn_recv_sock() */
+	rcu_assign_sk_user_data(new_clcsock->sk, NULL);
+	write_unlock_bh(&new_clcsock->sk->sk_callback_lock);
 
 	(*new_smc)->clcsock = new_clcsock;
 out:

gemini-3.1-pro-preview

null

null

							input: 2307
							output: 29
							thoughts: 244
						

**Analyzing the SMC Patch and Fuzzing Potential**

Okay, so I'm looking at this patch for `net/smc/af_smc.c`, specifically how it modifies `smc_tcp_syn_recv_sock` and `smc_clcsock_accept`. The core of the change revolves around protecting `sk_user_data` to prevent a sockmap from interfering.

My thinking is that the patch adds locking around `rcu_assign_sk_user_data`, which makes sense. They're using `__rcu_assign_sk_user_data_with_flags(child, NULL, SK_USER_DATA_NOCOPY)` in `smc_tcp_syn_recv_sock` to essentially reserve the `sk_user_data` slot. This is a common pattern to avoid races, but it's important to understand the flow. Then, `smc_clcsock_accept` subsequently releases that reservation using `rcu_assign_sk_user_data(new_clcsock->sk, NULL)` within the `sk_callback_lock` context.

Now, for my immediate concern: Is this something fuzzable? Absolutely. It’s part of the network stack; SMC (AF_SMC) is the obvious target. The critical functions here are `smc_tcp_syn_recv_sock` and `smc_clcsock_accept`. These are my focus.

I need to confirm that `SMC` is enabled in the configuration, but that should be straightforward. So, my strategy is set: Enable the relevant configuration options and focus on these two functions for fuzzing.

{
  "Expression": "config SMC",
  "PathPrefix": "net/smc/Kconfig"
}

{
  "Output": "net/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: 3122
							output: 98
							thoughts: 118
						

**Analyzing the SMC Configuration and Associated Functions**

Okay, so the configuration in question is `SMC`, and my focus is on the functions `smc_tcp_syn_recv_sock` and `smc_clcsock_accept`. The context seems to be a patch that addresses a race condition, or perhaps a bug related to how the sockmap claims a slot. That's good, a fix is always welcome!

Before I dive too deep, I need to confirm something fundamental. I need to make sure these functions are actually *reachable* within the SMC protocol implementation. If they're not, then this patch, while functional, might not actually *do* anything in a meaningful way.

Alright, a quick look confirms it. `smc_tcp_syn_recv_sock` and `smc_clcsock_accept` are indeed part of the SMC protocol implementation. And SMC itself is reachable through a standard `socket(AF_SMC, ...)` call, which means we can trigger the code. Good, this all makes sense.

Now, I'll set the results. I have a clearer picture now.

{
  "EnableConfigs": [
    "SMC"
  ],
  "FocusSymbols": [
    "smc_tcp_syn_recv_sock",
    "smc_clcsock_accept"
  ],
  "Reasoning": "The patch modifies the socket accept and syn receive paths in the SMC protocol to prevent sockmap from claiming the sk_user_data slot. This is a functional change in the core SMC protocol logic.",
  "WorthFuzzing": true
}

{
  "EnableConfigs": [
    "SMC"
  ],
  "FocusSymbols": [
    "smc_tcp_syn_recv_sock",
    "smc_clcsock_accept"
  ],
  "Reasoning": "The patch modifies the socket accept and syn receive paths in the SMC protocol to prevent sockmap from claiming the sk_user_data slot. This is a functional change in the core SMC protocol logic.",
  "WorthFuzzing": true
}