AI Trajectory

null

{
  "EnableConfigs": [
    "IP_SCTP"
  ],
  "FocusSymbols": [
    "sctp_setsockopt_reset_streams",
    "sctp_setsockopt"
  ],
  "Reasoning": "The patch fixes a bug in the calculation of the maximum `optlen` for the `SCTP_RESET_STREAMS` socket option. The previous calculation incorrectly limited the number of streams that could be reset to ~32K instead of the intended ~64K. This is a functional change in the SCTP setsockopt handler that should be fuzzed to ensure the new bounds checking is correct and doesn't introduce any out-of-bounds access.",
  "WorthFuzzing": true
}

null

{
  "PatchDiff": "commit 85662b790e86192c94e678b1cded6741ea9a11dc\nAuthor: syz-cluster \u003ctriage@syzkaller.com\u003e\nDate:   Wed Jun 24 12:46:53 2026 +0000\n\n    syz-cluster: applied patch under review\n\ndiff --git a/net/sctp/socket.c b/net/sctp/socket.c\nindex 66e12fb0c646ad..b8f13044a21915 100644\n--- a/net/sctp/socket.c\n+++ b/net/sctp/socket.c\n@@ -4111,8 +4111,9 @@ static int sctp_setsockopt_reset_streams(struct sock *sk,\n \tif (optlen \u003c sizeof(*params))\n \t\treturn -EINVAL;\n \t/* srs_number_streams is u16, so optlen can't be bigger than this. */\n-\toptlen = min_t(unsigned int, optlen, USHRT_MAX +\n-\t\t\t\t\t     sizeof(__u16) * sizeof(*params));\n+\toptlen = min_t(unsigned int, optlen,\n+\t\t       struct_size_t(struct sctp_reset_streams, srs_stream_list,\n+\t\t\t\t     USHRT_MAX));\n \n \tif (params-\u003esrs_number_streams * sizeof(__u16) \u003e\n \t    optlen - sizeof(*params))\n@@ -4598,8 +4599,8 @@ static int sctp_setsockopt(struct sock *sk, int level, int optname,\n \tif (optlen \u003e 0) {\n \t\t/* Trim it to the biggest size sctp sockopt may need if necessary */\n \t\toptlen = min_t(unsigned int, optlen,\n-\t\t\t       PAGE_ALIGN(USHRT_MAX +\n-\t\t\t\t\t  sizeof(__u16) * sizeof(struct sctp_reset_streams)));\n+\t\t\t       PAGE_ALIGN(struct_size_t(struct sctp_reset_streams,\n+\t\t\t\t\t\t\tsrs_stream_list, USHRT_MAX)));\n \t\tkopt = memdup_sockptr(optval, optlen);\n \t\tif (IS_ERR(kopt))\n \t\t\treturn PTR_ERR(kopt);\n"
}

gemini-3.1-pro-preview

null

{
  "EnableConfigs": [
    "IP_SCTP"
  ],
  "FocusSymbols": [
    "sctp_setsockopt_reset_streams",
    "sctp_setsockopt"
  ],
  "Reasoning": "The patch fixes a bug in the calculation of the maximum `optlen` for the `SCTP_RESET_STREAMS` socket option. The previous calculation incorrectly limited the number of streams that could be reset to ~32K instead of the intended ~64K. This is a functional change in the SCTP setsockopt handler that should be fuzzed to ensure the new bounds checking is correct and doesn't introduce any out-of-bounds access.",
  "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 85662b790e86192c94e678b1cded6741ea9a11dc
Author: syz-cluster <triage@syzkaller.com>
Date:   Wed Jun 24 12:46:53 2026 +0000

    syz-cluster: applied patch under review

diff --git a/net/sctp/socket.c b/net/sctp/socket.c
index 66e12fb0c646ad..b8f13044a21915 100644
--- a/net/sctp/socket.c
+++ b/net/sctp/socket.c
@@ -4111,8 +4111,9 @@ static int sctp_setsockopt_reset_streams(struct sock *sk,
 	if (optlen < sizeof(*params))
 		return -EINVAL;
 	/* srs_number_streams is u16, so optlen can't be bigger than this. */
-	optlen = min_t(unsigned int, optlen, USHRT_MAX +
-					     sizeof(__u16) * sizeof(*params));
+	optlen = min_t(unsigned int, optlen,
+		       struct_size_t(struct sctp_reset_streams, srs_stream_list,
+				     USHRT_MAX));
 
 	if (params->srs_number_streams * sizeof(__u16) >
 	    optlen - sizeof(*params))
@@ -4598,8 +4599,8 @@ static int sctp_setsockopt(struct sock *sk, int level, int optname,
 	if (optlen > 0) {
 		/* Trim it to the biggest size sctp sockopt may need if necessary */
 		optlen = min_t(unsigned int, optlen,
-			       PAGE_ALIGN(USHRT_MAX +
-					  sizeof(__u16) * sizeof(struct sctp_reset_streams)));
+			       PAGE_ALIGN(struct_size_t(struct sctp_reset_streams,
+							srs_stream_list, USHRT_MAX)));
 		kopt = memdup_sockptr(optval, optlen);
 		if (IS_ERR(kopt))
 			return PTR_ERR(kopt);

gemini-3.1-pro-preview

null

null

							input: 2122
							output: 40
							thoughts: 882
						

**Analyzing a Patch in net/sctp/socket.c**

Okay, so I'm looking at a patch in `net/sctp/socket.c` that modifies how `optlen` is calculated within the `sctp_setsockopt_reset_streams` and `sctp_setsockopt` functions. It seems they're switching from using a simple arithmetic calculation to the `struct_size_t` macro. Let's dig in.

The old code calculates the size limit as `USHRT_MAX + sizeof(__u16) * sizeof(*params)`.  `*params`, in this context, is a `struct sctp_reset_streams`.  `sizeof(__u16)` is, of course, 2 bytes. The new code leverages `struct_size_t(struct sctp_reset_streams, srs_stream_list, USHRT_MAX)`. This macro should compute `sizeof(struct sctp_reset_streams) + USHRT_MAX * sizeof(srs_stream_list[0])`.

Now, if I break this down, the old code was limiting `optlen` to `65535 + 2 * sizeof(struct sctp_reset_streams)`. I assumed that `sizeof(struct sctp_reset_streams)` was 8, which makes the limit to roughly 65551 bytes.  However, with the new code using `struct_size_t` with an array of `__u16`, the total size should be `sizeof(struct sctp_reset_streams) + USHRT_MAX * 2`, or approximately 131078 bytes. Therefore, the old code actually had a bug, because it was incorrectly limiting the buffer size. It essentially capped the allowable length at ~64KB instead of closer to ~128KB.

The calculation error was that the old code was effectively capping the maximum size to 65551, which would imply that `srs_number_streams` was also limited, and it was. By capping `optlen` at 65551, any value of `srs_number_streams` greater than 32771 would lead to an incorrect value calculation. It seems the new approach correctly calculates the size required, effectively fixing this limitation.

To solidify my understanding, I need to confirm the use of `struct sctp_reset_streams` elsewhere in the codebase. I should use a tool like `grepper` to confirm this before I move on.

{
  "Expression": "struct sctp_reset_streams",
  "PathPrefix": "include/uapi/linux/sctp.h"
}

{
  "Output": "include/uapi/linux/sctp.h=1119=struct sctp_info {\n--\ninclude/uapi/linux/sctp.h-1182-\ninclude/uapi/linux/sctp.h:1183:struct sctp_reset_streams {\ninclude/uapi/linux/sctp.h-1184-\tsctp_assoc_t srs_assoc_id;\n"
}

gemini-3.1-pro-preview

null

null

							input: 3727
							output: 41
							thoughts: 26
						

Here's my attempt at summarizing the thought process, tailored for an expert audience:

**Diving into SCTP Header Structures**

Okay, I need to refresh my memory on the specifics of the SCTP protocol, particularly the association and address management aspects. Let's start by looking at the kernel's definition. Line 1183 in `include/uapi/linux/sctp.h` is likely a good starting point. I suspect that's where the key structures for association parameters or maybe address configuration, or perhaps even chunk definitions begin. It's time to dig in and see what's defined around that area. Gotta brush up my knowledge on the details to continue working on this.

{
  "File": "include/uapi/linux/sctp.h",
  "FirstLine": 1180,
  "LineCount": 20
}

{
  "Contents": "1180:\t\t__u32\t__reserved3;\n1181:\t};\n1182:\t\n1183:\tstruct sctp_reset_streams {\n1184:\t\tsctp_assoc_t srs_assoc_id;\n1185:\t\tuint16_t srs_flags;\n1186:\t\tuint16_t srs_number_streams;\t/* 0 == ALL */\n1187:\t\tuint16_t srs_stream_list[];\t/* list if srs_num_streams is not 0 */\n1188:\t};\n1189:\t\n1190:\tstruct sctp_add_streams {\n1191:\t\tsctp_assoc_t sas_assoc_id;\n1192:\t\tuint16_t sas_instrms;\n1193:\t\tuint16_t sas_outstrms;\n1194:\t};\n1195:\t\n1196:\tstruct sctp_event {\n1197:\t\tsctp_assoc_t se_assoc_id;\n1198:\t\tuint16_t se_type;\n1199:\t\tuint8_t se_on;\n"
}

gemini-3.1-pro-preview

null

null

							input: 4268
							output: 40
							thoughts: 292
						

**Analyzing the SCTP Reset Streams Structure**

Okay, let's break this down. It seems we're dealing with the `sctp_reset_streams` structure and a potential size change. I see that `sctp_assoc_t` is a 4-byte integer, and `srs_flags` and `srs_number_streams` are both 2 bytes. That puts the basic `sctp_reset_streams` struct at 8 bytes, which makes sense.

Now, the old code used `USHRT_MAX + sizeof(__u16) * sizeof(*params)`. We know `sizeof(*params)` is 8 and `sizeof(__u16)` is 2, leading to `USHRT_MAX + 16`, or 65551. So, with this old method, there appears to be a limit.

However, the new code uses `struct_size_t(struct sctp_reset_streams, srs_stream_list, USHRT_MAX)`, expanding the size to the equivalent of `sizeof(struct sctp_reset_streams) + USHRT_MAX * sizeof(uint16_t)`. This translates to `8 + 65535 * 2 = 131078`. Bingo! This is a *definite* functional change.

This means we've effectively increased the maximum allowable value for `srs_number_streams` from roughly 32771 to 65535. This is a significant bump, and it's something we *absolutely* need to fuzz. Any change like this warrants thorough testing to ensure stability and catch any potential edge cases.

I should probably dive into `sctp_setsockopt_reset_streams` in `net/sctp/socket.c` and take a closer look at how this new size is handled at the socket option level. We need to make sure the interface can correctly handle the increased stream count.

{
  "Expression": "sctp_setsockopt_reset_streams",
  "PathPrefix": "net/sctp/socket.c"
}

{
  "Output": "net/sctp/socket.c=4063=static int sctp_setsockopt_enable_strreset(struct sock *sk,\n--\nnet/sctp/socket.c-4104-\nnet/sctp/socket.c:4105:static int sctp_setsockopt_reset_streams(struct sock *sk,\nnet/sctp/socket.c-4106-\t\t\t\t\t struct sctp_reset_streams *params,\n--\nnet/sctp/socket.c=4579=static int sctp_setsockopt(struct sock *sk, int level, int optname,\n--\nnet/sctp/socket.c-4746-\tcase SCTP_RESET_STREAMS:\nnet/sctp/socket.c:4747:\t\tretval = sctp_setsockopt_reset_streams(sk, kopt, optlen);\nnet/sctp/socket.c-4748-\t\tbreak;\n"
}

gemini-3.1-pro-preview

null

null

							input: 5291
							output: 34
							thoughts: 79
						

Okay, here's my take on those thoughts, framed as my own mental processing:

**Prioritizing Fuzzing Targets in SCTP**

Right, so `sctp_setsockopt_reset_streams` is triggered by a call from `sctp_setsockopt` specifically when `SCTP_RESET_STREAMS` is the option being set. That's key. Considering my goal of effective fuzzing, it's pretty clear where I should be concentrating my efforts: I need to deeply explore the interaction within `sctp_setsockopt_reset_streams` itself and, of course, the broader implications when it's called from `sctp_setsockopt`. These are the most direct entry points, and likely, where the most interesting, and potentially exploitable, behavior will reside.

Before I go any deeper, I should make sure that SCTP is even enabled in the kernel config. Let me check the Kconfig files, just to confirm that this functionality is actually compiled in. No point digging into code that doesn't exist, as this could have been compiled out.

{
  "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: 5708
							output: 34
							thoughts: 22
						

Okay, here's my take on those thoughts, framed from a first-person perspective as a specialist:

**Initial Configuration Check**

Alright, the current configuration in play is `IP_SCTP`. My first thought is, "Okay, let's establish the context." This suggests an SCTP implementation utilizing the IP protocol, but that's just the initial starting point. My next step, as always, will be to verify this is the *only* active configuration or if there are other parameters influencing the overall system behavior. I need a clear picture. Are there any other configuration parameters I need to be aware of? Are there potentially conflicting settings I should check? Gotta make sure I'm seeing the whole picture and not missing a critical piece of the puzzle.

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

{
  "Contents": "   1:\t# SPDX-License-Identifier: GPL-2.0-only\n   2:\t#\n   3:\t# SCTP configuration\n   4:\t#\n   5:\t\n   6:\tmenuconfig IP_SCTP\n   7:\t\ttristate \"The SCTP Protocol\"\n   8:\t\tdepends on INET\n   9:\t\tselect CRYPTO_LIB_SHA1\n  10:\t\tselect CRYPTO_LIB_SHA256\n  11:\t\tselect CRYPTO_LIB_UTILS\n  12:\t\tselect NET_CRC32C\n  13:\t\tselect NET_UDP_TUNNEL\n  14:\t\thelp\n  15:\t\t  Stream Control Transmission Protocol\n  16:\t\n  17:\t\t  From RFC 2960 \u003chttp://www.ietf.org/rfc/rfc2960.txt\u003e.\n  18:\t\n  19:\t\t  \"SCTP is a reliable transport protocol operating on top of a\n  20:\t\t  connectionless packet network such as IP.  It offers the following\n"
}

gemini-3.1-pro-preview

null

null

							input: 6190
							output: 38
							thoughts: 77
						

Okay, here's my quick rundown of what I'm thinking about with that `IP_SCTP` config:

**Analyzing `sctp_setsockopt_reset_streams`**

Alright, the context is `IP_SCTP`, good. Now, I'm just quickly confirming that `sctp_setsockopt_reset_streams` is actually something we can get to. It is, right? It's a pretty standard setsockopt handler for SCTP sockets, so logically, it should be. Yep, confirmed.

Now, just to be absolutely certain, let me pull up the implementation of `sctp_setsockopt_reset_streams` and give it another once-over. Gotta make sure there are no gotchas there.

{
  "File": "net/sctp/socket.c",
  "FirstLine": 4105,
  "LineCount": 50
}

{
  "Contents": "4105:\tstatic int sctp_setsockopt_reset_streams(struct sock *sk,\n4106:\t\t\t\t\t\t struct sctp_reset_streams *params,\n4107:\t\t\t\t\t\t unsigned int optlen)\n4108:\t{\n4109:\t\tstruct sctp_association *asoc;\n4110:\t\n4111:\t\tif (optlen \u003c sizeof(*params))\n4112:\t\t\treturn -EINVAL;\n4113:\t\t/* srs_number_streams is u16, so optlen can't be bigger than this. */\n4114:\t\toptlen = min_t(unsigned int, optlen,\n4115:\t\t\t       struct_size_t(struct sctp_reset_streams, srs_stream_list,\n4116:\t\t\t\t\t     USHRT_MAX));\n4117:\t\n4118:\t\tif (params-\u003esrs_number_streams * sizeof(__u16) \u003e\n4119:\t\t    optlen - sizeof(*params))\n4120:\t\t\treturn -EINVAL;\n4121:\t\n4122:\t\tasoc = sctp_id2assoc(sk, params-\u003esrs_assoc_id);\n4123:\t\tif (!asoc)\n4124:\t\t\treturn -EINVAL;\n4125:\t\n4126:\t\treturn sctp_send_reset_streams(asoc, params);\n4127:\t}\n4128:\t\n4129:\tstatic int sctp_setsockopt_reset_assoc(struct sock *sk, sctp_assoc_t *associd,\n4130:\t\t\t\t\t       unsigned int optlen)\n4131:\t{\n4132:\t\tstruct sctp_association *asoc;\n4133:\t\n4134:\t\tif (optlen != sizeof(*associd))\n4135:\t\t\treturn -EINVAL;\n4136:\t\n4137:\t\tasoc = sctp_id2assoc(sk, *associd);\n4138:\t\tif (!asoc)\n4139:\t\t\treturn -EINVAL;\n4140:\t\n4141:\t\treturn sctp_send_reset_assoc(asoc);\n4142:\t}\n4143:\t\n4144:\tstatic int sctp_setsockopt_add_streams(struct sock *sk,\n4145:\t\t\t\t\t       struct sctp_add_streams *params,\n4146:\t\t\t\t\t       unsigned int optlen)\n4147:\t{\n4148:\t\tstruct sctp_association *asoc;\n4149:\t\n4150:\t\tif (optlen != sizeof(*params))\n4151:\t\t\treturn -EINVAL;\n4152:\t\n4153:\t\tasoc = sctp_id2assoc(sk, params-\u003esas_assoc_id);\n4154:\t\tif (!asoc)\n"
}

gemini-3.1-pro-preview

null

null

							input: 7234
							output: 159
							thoughts: 193
						

**Analyzing the SCTP Stream Reset Fix**

Okay, so I've got a patch here that's caught my eye. The code itself is definitely reachable and appears to be functioning as expected. It's targeting a specific bug related to the `SCTP_RESET_STREAMS` socket option. Looks like they've corrected a limitation where the `optlen` (option length) was capped too aggressively at 65551, when it should have been closer to 131078. This was directly impacting the number of streams that could be reset—effectively limiting the operation to just over 32,000 streams when the design clearly intended for double that.

My focus is naturally on `sctp_setsockopt_reset_streams` and, more broadly, `sctp_setsockopt` itself. These are the key functions involved, the heart of the changes. The `IP_SCTP` config is, obviously, a key enabler here.

The core of the matter is this: they've updated the logic used to determine the maximum length of the option data for stream reset. This is a functional change, a real improvement to how the SCTP socket option is handled. Now, with the upper bound fixed, my primary concern shifts to fuzzing. I need to ensure that this new bounds checking is rock solid. I have to verify that the fix addresses the initial issue, and, critically, that it *doesn't* introduce any new vulnerabilities, like out-of-bounds memory accesses. I'll need to develop fuzzing strategies specifically to exercise these new boundaries and ensure the code is robust.

{
  "EnableConfigs": [
    "IP_SCTP"
  ],
  "FocusSymbols": [
    "sctp_setsockopt_reset_streams",
    "sctp_setsockopt"
  ],
  "Reasoning": "The patch fixes a bug in the calculation of the maximum `optlen` for the `SCTP_RESET_STREAMS` socket option. The previous calculation incorrectly limited the number of streams that could be reset to ~32K instead of the intended ~64K. This is a functional change in the SCTP setsockopt handler that should be fuzzed to ensure the new bounds checking is correct and doesn't introduce any out-of-bounds access.",
  "WorthFuzzing": true
}

{
  "EnableConfigs": [
    "IP_SCTP"
  ],
  "FocusSymbols": [
    "sctp_setsockopt_reset_streams",
    "sctp_setsockopt"
  ],
  "Reasoning": "The patch fixes a bug in the calculation of the maximum `optlen` for the `SCTP_RESET_STREAMS` socket option. The previous calculation incorrectly limited the number of streams that could be reset to ~32K instead of the intended ~64K. This is a functional change in the SCTP setsockopt handler that should be fuzzed to ensure the new bounds checking is correct and doesn't introduce any out-of-bounds access.",
  "WorthFuzzing": true
}