AI Trajectory

null

{
  "EnableConfigs": [
    "UNIX"
  ],
  "FocusSymbols": [
    "unix_schedule_gc",
    "unix_prepare_fpl",
    "unix_release_sock"
  ],
  "Reasoning": "The patch modifies the garbage collection scheduling logic for AF_UNIX sockets. It removes the GC scheduling from `unix_prepare_fpl` (called when sending file descriptors) and simplifies `unix_schedule_gc` by removing the penalty for users with many inflight sockets. This is a functional change to core AF_UNIX socket lifecycle and garbage collection.",
  "WorthFuzzing": true
}

null

{
  "PatchDiff": "commit de882d7632bb676c4c5c711f5f2b9049bd6e4f5d\nAuthor: syz-cluster \u003ctriage@syzkaller.com\u003e\nDate:   Wed Jul 1 23:45:24 2026 +0000\n\n    syz-cluster: applied patch under review\n\ndiff --git a/net/unix/af_unix.c b/net/unix/af_unix.c\nindex f7a9d55eee8a12..759db734a86646 100644\n--- a/net/unix/af_unix.c\n+++ b/net/unix/af_unix.c\n@@ -733,7 +733,7 @@ static void unix_release_sock(struct sock *sk, int embrion)\n \n \t/* ---- Socket is dead now and most probably destroyed ---- */\n \n-\tunix_schedule_gc(NULL);\n+\tunix_schedule_gc();\n }\n \n struct unix_peercred {\ndiff --git a/net/unix/af_unix.h b/net/unix/af_unix.h\nindex 8119dbeef3a3c6..600d56fdcde4c1 100644\n--- a/net/unix/af_unix.h\n+++ b/net/unix/af_unix.h\n@@ -30,7 +30,7 @@ void unix_update_edges(struct unix_sock *receiver);\n int unix_prepare_fpl(struct scm_fp_list *fpl);\n void unix_destroy_fpl(struct scm_fp_list *fpl);\n void unix_peek_fpl(struct scm_fp_list *fpl);\n-void unix_schedule_gc(struct user_struct *user);\n+void unix_schedule_gc(void);\n \n /* SOCK_DIAG */\n long unix_inq_len(struct sock *sk);\ndiff --git a/net/unix/garbage.c b/net/unix/garbage.c\nindex 0783555e252660..d46aeb9d205189 100644\n--- a/net/unix/garbage.c\n+++ b/net/unix/garbage.c\n@@ -300,8 +300,6 @@ int unix_prepare_fpl(struct scm_fp_list *fpl)\n \tif (!fpl-\u003eedges)\n \t\tgoto err;\n \n-\tunix_schedule_gc(fpl-\u003euser);\n-\n \treturn 0;\n \n err:\n@@ -637,23 +635,11 @@ static void unix_gc(struct work_struct *work)\n \n static DECLARE_WORK(unix_gc_work, unix_gc);\n \n-#define UNIX_INFLIGHT_SANE_USER\t\t(SCM_MAX_FD * 8)\n-\n-void unix_schedule_gc(struct user_struct *user)\n+void unix_schedule_gc(void)\n {\n \tif (READ_ONCE(unix_graph_state) == UNIX_GRAPH_NOT_CYCLIC)\n \t\treturn;\n \n-\t/* Penalise users who want to send AF_UNIX sockets\n-\t * but whose sockets have not been received yet.\n-\t */\n-\tif (user \u0026\u0026\n-\t    READ_ONCE(user-\u003eunix_inflight) \u003c UNIX_INFLIGHT_SANE_USER)\n-\t\treturn;\n-\n \tif (!READ_ONCE(gc_in_progress))\n \t\tqueue_work(system_dfl_wq, \u0026unix_gc_work);\n-\n-\tif (user \u0026\u0026 READ_ONCE(unix_graph_cyclic_sccs))\n-\t\tflush_work(\u0026unix_gc_work);\n }\n"
}

gemini-3.1-pro-preview

null

{
  "EnableConfigs": [
    "UNIX"
  ],
  "FocusSymbols": [
    "unix_schedule_gc",
    "unix_prepare_fpl",
    "unix_release_sock"
  ],
  "Reasoning": "The patch modifies the garbage collection scheduling logic for AF_UNIX sockets. It removes the GC scheduling from `unix_prepare_fpl` (called when sending file descriptors) and simplifies `unix_schedule_gc` by removing the penalty for users with many inflight sockets. This is a functional change to core AF_UNIX socket lifecycle and garbage collection.",
  "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 de882d7632bb676c4c5c711f5f2b9049bd6e4f5d
Author: syz-cluster <triage@syzkaller.com>
Date:   Wed Jul 1 23:45:24 2026 +0000

    syz-cluster: applied patch under review

diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c
index f7a9d55eee8a12..759db734a86646 100644
--- a/net/unix/af_unix.c
+++ b/net/unix/af_unix.c
@@ -733,7 +733,7 @@ static void unix_release_sock(struct sock *sk, int embrion)
 
 	/* ---- Socket is dead now and most probably destroyed ---- */
 
-	unix_schedule_gc(NULL);
+	unix_schedule_gc();
 }
 
 struct unix_peercred {
diff --git a/net/unix/af_unix.h b/net/unix/af_unix.h
index 8119dbeef3a3c6..600d56fdcde4c1 100644
--- a/net/unix/af_unix.h
+++ b/net/unix/af_unix.h
@@ -30,7 +30,7 @@ void unix_update_edges(struct unix_sock *receiver);
 int unix_prepare_fpl(struct scm_fp_list *fpl);
 void unix_destroy_fpl(struct scm_fp_list *fpl);
 void unix_peek_fpl(struct scm_fp_list *fpl);
-void unix_schedule_gc(struct user_struct *user);
+void unix_schedule_gc(void);
 
 /* SOCK_DIAG */
 long unix_inq_len(struct sock *sk);
diff --git a/net/unix/garbage.c b/net/unix/garbage.c
index 0783555e252660..d46aeb9d205189 100644
--- a/net/unix/garbage.c
+++ b/net/unix/garbage.c
@@ -300,8 +300,6 @@ int unix_prepare_fpl(struct scm_fp_list *fpl)
 	if (!fpl->edges)
 		goto err;
 
-	unix_schedule_gc(fpl->user);
-
 	return 0;
 
 err:
@@ -637,23 +635,11 @@ static void unix_gc(struct work_struct *work)
 
 static DECLARE_WORK(unix_gc_work, unix_gc);
 
-#define UNIX_INFLIGHT_SANE_USER		(SCM_MAX_FD * 8)
-
-void unix_schedule_gc(struct user_struct *user)
+void unix_schedule_gc(void)
 {
 	if (READ_ONCE(unix_graph_state) == UNIX_GRAPH_NOT_CYCLIC)
 		return;
 
-	/* Penalise users who want to send AF_UNIX sockets
-	 * but whose sockets have not been received yet.
-	 */
-	if (user &&
-	    READ_ONCE(user->unix_inflight) < UNIX_INFLIGHT_SANE_USER)
-		return;
-
 	if (!READ_ONCE(gc_in_progress))
 		queue_work(system_dfl_wq, &unix_gc_work);
-
-	if (user && READ_ONCE(unix_graph_cyclic_sccs))
-		flush_work(&unix_gc_work);
 }

gemini-3.1-pro-preview

null

null

							input: 2467
							output: 20
							thoughts: 462
						

**Analyzing the AF_UNIX Garbage Collection Patch**

Okay, so I'm looking at this patch for AF_UNIX, and it's making some pretty significant changes to garbage collection. Specifically, it seems like they're removing the `user` argument from `unix_schedule_gc()` and simplifying its logic. My initial thought is to figure out the reasoning behind this removal.

Looking at the code, the most immediate change is the removal of the user-specific checks within `unix_schedule_gc()`. Previously, it penalized users with a high number of inflight AF_UNIX sockets and it contained a `flush_work` call under certain conditions which I understand. This patch removes those checks entirely, meaning we're losing that user-based throttling and that particular triggering mechanism.

The consequence is that `unix_schedule_gc()` is now unconditionally scheduled (assuming the garbage collection preconditions are met). It looks like the patch removes the penalization of users with many inflight sockets, which is an interesting decision. I'll need to think about the implications here.

Further, I see that the patch also removes the call to `unix_schedule_gc()` from `unix_prepare_fpl()`. That's another key change. It removes a specific trigger for garbage collection, which has significant implications for how often we will execute garbage collection.

Overall, it looks like this patch is simplifying the garbage collection logic, removing user-specific considerations, and changing when it's triggered. I'll need to dig deeper into the rationale behind these changes, and ensure we're not introducing any regressions or performance issues. I need to understand why they're removing the user-based checks and the specific trigger in `unix_prepare_fpl()`. I should really check where `unix_prepare_fpl()` is called now to get a better overview.

{
  "Expression": "unix_prepare_fpl"
}

{
  "Output": "net/unix/af_unix.c=1935=static int unix_attach_fds(struct scm_cookie *scm, struct sk_buff *skb)\n--\nnet/unix/af_unix.c-1942-\nnet/unix/af_unix.c:1943:\tif (unix_prepare_fpl(UNIXCB(skb).fp))\nnet/unix/af_unix.c-1944-\t\treturn -ENOMEM;\n--\nnet/unix/af_unix.h=29=void unix_update_edges(struct unix_sock *receiver);\nnet/unix/af_unix.h:30:int unix_prepare_fpl(struct scm_fp_list *fpl);\nnet/unix/af_unix.h-31-void unix_destroy_fpl(struct scm_fp_list *fpl);\n--\nnet/unix/garbage.c=266=void unix_update_edges(struct unix_sock *receiver)\n--\nnet/unix/garbage.c-281-\nnet/unix/garbage.c:282:int unix_prepare_fpl(struct scm_fp_list *fpl)\nnet/unix/garbage.c-283-{\n"
}

gemini-3.1-pro-preview

null

null

							input: 3653
							output: 28
							thoughts: 143
						

**Initial Assessment of AF_UNIX File Descriptor Handling**

Okay, so I'm looking at this patch and it's modifying core AF_UNIX socket logic – specifically around file descriptor handling. The function `unix_prepare_fpl` is key here, as it's called from `unix_attach_fds`, which itself is invoked when we're sending file descriptors over an AF_UNIX socket. The changes are clearly functional and it's definitely something that warrants a thorough fuzzing campaign. The configuration option that governs AF_UNIX support is `UNIX`, that's good to know.

I should also check the functions surrounding `unix_prepare_fpl`. I should make sure to look at `unix_schedule_gc`. I see it's now simpler and parameterless, which is always a good sign. `unix_prepare_fpl` itself has been modified, of course, and `unix_release_sock` also seems to be impacted by these changes. I'll need to go back and cross-reference the Kconfig file for `UNIX` to see if there's any related dependencies or configuration that might be relevant.

{
  "Expression": "config UNIX",
  "PathPrefix": "net/unix/Kconfig"
}

{
  "Output": "net/unix/Kconfig-5-\nnet/unix/Kconfig:6:config UNIX\nnet/unix/Kconfig-7-\tbool \"Unix domain sockets\"\n--\nnet/unix/Kconfig=19=config\tAF_UNIX_OOB\n--\nnet/unix/Kconfig-25-\nnet/unix/Kconfig:26:config UNIX_DIAG\nnet/unix/Kconfig-27-\ttristate \"UNIX: socket monitoring interface\"\n"
}

gemini-3.1-pro-preview

null

null

							input: 4196
							output: 19
							thoughts: 102
						

**Analyzing the UNIX Configuration**

Okay, so I'm looking at this `UNIX` config, which I see is a boolean – pretty straightforward. My focus is on these symbols: `unix_schedule_gc`, `unix_prepare_fpl`, and `unix_release_sock`. I seem to recall that `unix_schedule_gc` *used* to be called from both `unix_release_sock` and `unix_prepare_fpl`. Ah, but a quick scan reveals that `unix_prepare_fpl` doesn't call it anymore, which is interesting.

Now, I need to understand the implications of that change. My next step is to comprehensively check *everywhere* `unix_schedule_gc` is invoked. I need to make sure I'm not missing any other potential call points, as this could have unforeseen ramifications. The change to `unix_prepare_fpl` warrants careful scrutiny and a complete audit of its usage.

{
  "Expression": "unix_schedule_gc"
}

{
  "Output": "net/unix/af_unix.c=665=static void unix_release_sock(struct sock *sk, int embrion)\n--\nnet/unix/af_unix.c-735-\nnet/unix/af_unix.c:736:\tunix_schedule_gc();\nnet/unix/af_unix.c-737-}\n--\nnet/unix/af_unix.h=32=void unix_peek_fpl(struct scm_fp_list *fpl);\nnet/unix/af_unix.h:33:void unix_schedule_gc(void);\nnet/unix/af_unix.h-34-\n--\nnet/unix/garbage.c=636=static DECLARE_WORK(unix_gc_work, unix_gc);\nnet/unix/garbage.c-637-\nnet/unix/garbage.c:638:void unix_schedule_gc(void)\nnet/unix/garbage.c-639-{\n"
}

gemini-3.1-pro-preview

null

null

							input: 4771
							output: 133
							thoughts: 254
						

**Analyzing the AF_UNIX Socket Garbage Collection Change**

Okay, so I'm digging into this patch. I see that `unix_schedule_gc` is *now* only called from `unix_release_sock`. Hang on a second... wasn't it also called from `unix_prepare_fpl` before? Yep, the patch definitely removes that call. That's a pretty significant functional change, affecting how garbage collection is scheduled for AF_UNIX sockets. This is going to have performance implications.

My focus symbols here are crystal clear: `unix_schedule_gc`, `unix_prepare_fpl`, and `unix_release_sock`. `unix_release_sock` is the socket close function, so GC is *only* triggered when a socket is released. `unix_prepare_fpl` is involved with sending file descriptors, which has a very different life cycle and performance profile. Excellent, that's what I needed.

My reasoning? This patch drastically alters the AF_UNIX garbage collection scheduling logic. We're getting rid of the penalty for users with many inflight sockets, *and* removing the GC scheduling from `unix_prepare_fpl`, which impacts the AF_UNIX socket lifecycle and garbage collection. This is a core change.

I need to confirm the relevant configuration. Looks like it's `UNIX` – a quick check confirms this. Are there any other relevant configs, though? Nope, `UNIX` seems to be the main one. I have what I need.

{
  "EnableConfigs": [
    "UNIX"
  ],
  "FocusSymbols": [
    "unix_schedule_gc",
    "unix_prepare_fpl",
    "unix_release_sock"
  ],
  "Reasoning": "The patch modifies the garbage collection scheduling logic for AF_UNIX sockets. It removes the GC scheduling from `unix_prepare_fpl` (called when sending file descriptors) and simplifies `unix_schedule_gc` by removing the penalty for users with many inflight sockets. This is a functional change to core AF_UNIX socket lifecycle and garbage collection.",
  "WorthFuzzing": true
}

{
  "EnableConfigs": [
    "UNIX"
  ],
  "FocusSymbols": [
    "unix_schedule_gc",
    "unix_prepare_fpl",
    "unix_release_sock"
  ],
  "Reasoning": "The patch modifies the garbage collection scheduling logic for AF_UNIX sockets. It removes the GC scheduling from `unix_prepare_fpl` (called when sending file descriptors) and simplifies `unix_schedule_gc` by removing the penalty for users with many inflight sockets. This is a functional change to core AF_UNIX socket lifecycle and garbage collection.",
  "WorthFuzzing": true
}