AI Trajectory

null

{
  "EnableConfigs": [
    "IP_SCTP"
  ],
  "FocusSymbols": [
    "sctp_sf_do_5_2_6_stale",
    "sctp_sf_cookie_echoed_err"
  ],
  "Reasoning": "The patch adds a bounds check in SCTP's stale cookie error handling to prevent an out-of-bounds read. This is a functional change in the core SCTP logic and should be fuzzed.",
  "WorthFuzzing": true
}

null

{
  "PatchDiff": "commit cc23d027e2ee39cbaae0c1f540d745a84fb0bd1e\nAuthor: syz-cluster \u003ctriage@syzkaller.com\u003e\nDate:   Sun Jul 5 01:06:41 2026 +0000\n\n    syz-cluster: applied patch under review\n\ndiff --git a/net/sctp/sm_statefuns.c b/net/sctp/sm_statefuns.c\nindex d23d935e128e96..e4b4b63162cf6c 100644\n--- a/net/sctp/sm_statefuns.c\n+++ b/net/sctp/sm_statefuns.c\n@@ -2592,6 +2592,9 @@ static enum sctp_disposition sctp_sf_do_5_2_6_stale(\n \n \terr = (struct sctp_errhdr *)(chunk-\u003eskb-\u003edata);\n \n+\tif ((u8 *)err + sizeof(*err) + sizeof(__be32) \u003e chunk-\u003echunk_end)\n+\t\treturn sctp_sf_pdiscard(net, ep, asoc, type, arg, commands);\n+\n \t/* When calculating the time extension, an implementation\n \t * SHOULD use the RTT information measured based on the\n \t * previous COOKIE ECHO / ERROR exchange, and should add no\n"
}

gemini-3.1-pro-preview

null

{
  "EnableConfigs": [
    "IP_SCTP"
  ],
  "FocusSymbols": [
    "sctp_sf_do_5_2_6_stale",
    "sctp_sf_cookie_echoed_err"
  ],
  "Reasoning": "The patch adds a bounds check in SCTP's stale cookie error handling to prevent an out-of-bounds read. This is a functional change in the core SCTP logic and 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 cc23d027e2ee39cbaae0c1f540d745a84fb0bd1e
Author: syz-cluster <triage@syzkaller.com>
Date:   Sun Jul 5 01:06:41 2026 +0000

    syz-cluster: applied patch under review

diff --git a/net/sctp/sm_statefuns.c b/net/sctp/sm_statefuns.c
index d23d935e128e96..e4b4b63162cf6c 100644
--- a/net/sctp/sm_statefuns.c
+++ b/net/sctp/sm_statefuns.c
@@ -2592,6 +2592,9 @@ static enum sctp_disposition sctp_sf_do_5_2_6_stale(
 
 	err = (struct sctp_errhdr *)(chunk->skb->data);
 
+	if ((u8 *)err + sizeof(*err) + sizeof(__be32) > chunk->chunk_end)
+		return sctp_sf_pdiscard(net, ep, asoc, type, arg, commands);
+
 	/* When calculating the time extension, an implementation
 	 * SHOULD use the RTT information measured based on the
 	 * previous COOKIE ECHO / ERROR exchange, and should add no

gemini-3.1-pro-preview

null

null

							input: 1890
							output: 34
							thoughts: 180
						

**SCTP Patch Analysis and Fuzzing Strategy**

Okay, so I'm looking at this patch for `net/sctp/sm_statefuns.c`. It's a pretty straightforward addition, a bounds check within `sctp_sf_do_5_2_6_stale`. Basically, it's guarding against a potential out-of-bounds read or something of that nature during error handling within the SCTP protocol, particularly when dealing with chunk processing. Functionally, this looks like a solid fix to a potential vulnerability.

Given the nature of the change—dealing with error handling and likely data validation, it's immediately obvious that this needs fuzzing. A bounds check like this is almost always added to avoid unexpected reads, so a fuzzing campaign to identify conditions the bounds check is meant to protect against would be prudent.

Now, let's get the build environment set up properly to test this. The primary configuration option I need to ensure SCTP is enabled is `CONFIG_IP_SCTP`. I'll need to check the Kconfig files, probably in `net/sctp/Kconfig` or something similar, to verify the exact dependencies and build-time configuration. This is standard procedure to confirm the code will be compiled and to tune any associated compile flags. From there, I'll need to develop fuzzing harnesses or utilize existing ones, focusing on crafted SCTP packets designed to trigger edge cases in the error path.

{
  "Expression": "config IP_SCTP",
  "PathPrefix": "net/sctp/Kconfig"
}

{
  "Output": "net/sctp/Kconfig-5-\nnet/sctp/Kconfig:6:menuconfig IP_SCTP\nnet/sctp/Kconfig-7-\ttristate \"The SCTP Protocol\"\n"
}

gemini-3.1-pro-preview

null

null

							input: 2480
							output: 49
							thoughts: 51
						

Here's my analysis of the situation:

**Investigating the `sctp_sf_do_5_2_6_stale` Function**

Okay, so the current configuration is set to `IP_SCTP`. My next step is to dive into the function `sctp_sf_do_5_2_6_stale`. I need to figure out how this function in `net/sctp/sm_statefuns.c` is handling things under this configuration. I'm going to start by reviewing the source code for that specific function. I'll need to pay close attention to the stale handling logic and see how it interacts with the state machine. Understanding its behavior within the SCTP context is crucial, given the `IP_SCTP` setting. I need to understand its edge cases as well to fully grasp its implications.

{
  "Expression": "sctp_sf_do_5_2_6_stale",
  "PathPrefix": "net/sctp/sm_statefuns.c"
}

{
  "Output": "net/sctp/sm_statefuns.c=65=static void sctp_send_stale_cookie_err(struct net *net,\n--\nnet/sctp/sm_statefuns.c-70-\t\t\t\t       struct sctp_chunk *err_chunk);\nnet/sctp/sm_statefuns.c:71:static enum sctp_disposition sctp_sf_do_5_2_6_stale(\nnet/sctp/sm_statefuns.c-72-\t\t\t\t\tstruct net *net,\n--\nnet/sctp/sm_statefuns.c=2505=enum sctp_disposition sctp_sf_cookie_echoed_err(\n--\nnet/sctp/sm_statefuns.c-2532-\t\tif (SCTP_ERROR_STALE_COOKIE == err-\u003ecause)\nnet/sctp/sm_statefuns.c:2533:\t\t\treturn sctp_sf_do_5_2_6_stale(net, ep, asoc, type,\nnet/sctp/sm_statefuns.c-2534-\t\t\t\t\t\t\targ, commands);\n--\nnet/sctp/sm_statefuns.c-2569- */\nnet/sctp/sm_statefuns.c:2570:static enum sctp_disposition sctp_sf_do_5_2_6_stale(\nnet/sctp/sm_statefuns.c-2571-\t\t\t\t\tstruct net *net,\n"
}

gemini-3.1-pro-preview

null

null

							input: 3165
							output: 42
							thoughts: 211
						

**Focusing on SCTP Stale Cookie Handling**

Okay, so I'm looking at this code and need to understand the relationship between `sctp_sf_do_5_2_6_stale` and `sctp_sf_cookie_echoed_err`. It looks like `sctp_sf_do_5_2_6_stale` is called from `sctp_sf_cookie_echoed_err`.  Given this connection, I should add both functions to `FocusSymbols`. That will give me a better handle on their interaction.

Now, before I proceed, I need to consider if any other configurations are necessary. From my experience with SCTP, `IP_SCTP` should be sufficient.

Alright, let's take a quick look at the code. I remember there was a question about whether `sctp_sf_do_5_2_6_stale` was static or not. Yup, it is declared static. Wait a minute! `sctp_sf_cookie_echoed_err` is *not* static. This means both functions can, and should, be added to `FocusSymbols` to fully understand the context.

Let's do a quick scan of `sctp_sf_do_5_2_6_stale` in `net/sctp/sm_statefuns.c`. That should refresh my memory of its internals and how it handles stale cookies.

{
  "File": "net/sctp/sm_statefuns.c",
  "FirstLine": 2570,
  "LineCount": 50
}

{
  "Contents": "2570:\tstatic enum sctp_disposition sctp_sf_do_5_2_6_stale(\n2571:\t\t\t\t\t\tstruct net *net,\n2572:\t\t\t\t\t\tconst struct sctp_endpoint *ep,\n2573:\t\t\t\t\t\tconst struct sctp_association *asoc,\n2574:\t\t\t\t\t\tconst union sctp_subtype type,\n2575:\t\t\t\t\t\tvoid *arg,\n2576:\t\t\t\t\t\tstruct sctp_cmd_seq *commands)\n2577:\t{\n2578:\t\tint attempts = asoc-\u003einit_err_counter + 1;\n2579:\t\tstruct sctp_chunk *chunk = arg, *reply;\n2580:\t\tstruct sctp_cookie_preserve_param bht;\n2581:\t\tstruct sctp_bind_addr *bp;\n2582:\t\tstruct sctp_errhdr *err;\n2583:\t\tu32 stale;\n2584:\t\n2585:\t\tif (attempts \u003e asoc-\u003emax_init_attempts) {\n2586:\t\t\tsctp_add_cmd_sf(commands, SCTP_CMD_SET_SK_ERR,\n2587:\t\t\t\t\tSCTP_ERROR(ETIMEDOUT));\n2588:\t\t\tsctp_add_cmd_sf(commands, SCTP_CMD_INIT_FAILED,\n2589:\t\t\t\t\tSCTP_PERR(SCTP_ERROR_STALE_COOKIE));\n2590:\t\t\treturn SCTP_DISPOSITION_DELETE_TCB;\n2591:\t\t}\n2592:\t\n2593:\t\terr = (struct sctp_errhdr *)(chunk-\u003eskb-\u003edata);\n2594:\t\n2595:\t\tif ((u8 *)err + sizeof(*err) + sizeof(__be32) \u003e chunk-\u003echunk_end)\n2596:\t\t\treturn sctp_sf_pdiscard(net, ep, asoc, type, arg, commands);\n2597:\t\n2598:\t\t/* When calculating the time extension, an implementation\n2599:\t\t * SHOULD use the RTT information measured based on the\n2600:\t\t * previous COOKIE ECHO / ERROR exchange, and should add no\n2601:\t\t * more than 1 second beyond the measured RTT, due to long\n2602:\t\t * State Cookie lifetimes making the endpoint more subject to\n2603:\t\t * a replay attack.\n2604:\t\t * Measure of Staleness's unit is usec. (1/1000000 sec)\n2605:\t\t * Suggested Cookie Life-span Increment's unit is msec.\n2606:\t\t * (1/1000 sec)\n2607:\t\t * In general, if you use the suggested cookie life, the value\n2608:\t\t * found in the field of measure of staleness should be doubled\n2609:\t\t * to give ample time to retransmit the new cookie and thus\n2610:\t\t * yield a higher probability of success on the reattempt.\n2611:\t\t */\n2612:\t\tstale = ntohl(*(__be32 *)((u8 *)err + sizeof(*err)));\n2613:\t\tstale = (stale * 2) / 1000;\n2614:\t\n2615:\t\tbht.param_hdr.type = SCTP_PARAM_COOKIE_PRESERVATIVE;\n2616:\t\tbht.param_hdr.length = htons(sizeof(bht));\n2617:\t\tbht.lifespan_increment = htonl(stale);\n2618:\t\n2619:\t\t/* Build that new INIT chunk.  */\n"
}

gemini-3.1-pro-preview

null

null

							input: 4671
							output: 114
							thoughts: 98
						

Okay, here's my assessment of this patch, from my perspective as someone who understands the intricacies of SCTP:

**Analyzing the SCTP Bounds Check**

Right, so this patch introduces a bounds check before we access the `stale` member of the `err` structure. That immediately signals a potential memory safety issue. The fact that they've identified an out-of-bounds read is concerning; these are precisely the types of vulnerabilities that can lead to crashes or, worse, exploitable flaws in the SCTP implementation. This is a clear functional change because, as experts, we know that such a check alters the program flow to ensure safe access.

Given the potential severity of out-of-bounds reads, fuzzing is an *excellent* idea. It’s an effective way to unearth subtle bugs that might not be apparent through static analysis. The `IP_SCTP` config also suggests the context of the bug, and the focus symbols, `sctp_sf_do_5_2_6_stale` and `sctp_sf_cookie_echoed_err`, pin down the critical areas this code is likely to change. Both of these symbols, coupled with `stale`, help us identify how and why the stale data might be a problem.

Let's call the set results, and work on it as soon as possible.

{
  "EnableConfigs": [
    "IP_SCTP"
  ],
  "FocusSymbols": [
    "sctp_sf_do_5_2_6_stale",
    "sctp_sf_cookie_echoed_err"
  ],
  "Reasoning": "The patch adds a bounds check in SCTP's stale cookie error handling to prevent an out-of-bounds read. This is a functional change in the core SCTP logic and should be fuzzed.",
  "WorthFuzzing": true
}

{
  "EnableConfigs": [
    "IP_SCTP"
  ],
  "FocusSymbols": [
    "sctp_sf_do_5_2_6_stale",
    "sctp_sf_cookie_echoed_err"
  ],
  "Reasoning": "The patch adds a bounds check in SCTP's stale cookie error handling to prevent an out-of-bounds read. This is a functional change in the core SCTP logic and should be fuzzed.",
  "WorthFuzzing": true
}