AI Trajectory

null

{
  "EnableConfigs": [
    "IP_SCTP"
  ],
  "FocusSymbols": [
    "sctp_assoc_bh_rcv",
    "sctp_endpoint_bh_rcv",
    "sctp_auth_chunk_verify"
  ],
  "Reasoning": "The patch fixes a potential NULL pointer dereference when skb_clone fails during SCTP chunk authentication. It modifies core SCTP receive path logic, which is reachable and functional.",
  "WorthFuzzing": true
}

null

{
  "PatchDiff": "commit 6b3917e93b4d22e1b1acf3be73c0c0d6f7852bce\nAuthor: syz-cluster \u003ctriage@syzkaller.com\u003e\nDate:   Mon Jul 20 13:32:21 2026 +0000\n\n    syz-cluster: applied patch under review\n\ndiff --git a/net/sctp/associola.c b/net/sctp/associola.c\nindex 62d3cc155809c7..e540683053960e 100644\n--- a/net/sctp/associola.c\n+++ b/net/sctp/associola.c\n@@ -999,7 +999,8 @@ static void sctp_assoc_bh_rcv(struct work_struct *work)\n \t\t\tif (next_hdr-\u003etype == SCTP_CID_COOKIE_ECHO) {\n \t\t\t\tchunk-\u003eauth_chunk = skb_clone(chunk-\u003eskb,\n \t\t\t\t\t\t\t      GFP_ATOMIC);\n-\t\t\t\tchunk-\u003eauth = 1;\n+\t\t\t\tif (chunk-\u003eauth_chunk)\n+\t\t\t\t\tchunk-\u003eauth = 1;\n \t\t\t\tcontinue;\n \t\t\t}\n \t\t}\ndiff --git a/net/sctp/endpointola.c b/net/sctp/endpointola.c\nindex dfb1719275dba7..3419748c66bc14 100644\n--- a/net/sctp/endpointola.c\n+++ b/net/sctp/endpointola.c\n@@ -368,7 +368,8 @@ static void sctp_endpoint_bh_rcv(struct work_struct *work)\n \t\t\tif (next_hdr-\u003etype == SCTP_CID_COOKIE_ECHO) {\n \t\t\t\tchunk-\u003eauth_chunk = skb_clone(chunk-\u003eskb,\n \t\t\t\t\t\t\t\tGFP_ATOMIC);\n-\t\t\t\tchunk-\u003eauth = 1;\n+\t\t\t\tif (chunk-\u003eauth_chunk)\n+\t\t\t\t\tchunk-\u003eauth = 1;\n \t\t\t\tcontinue;\n \t\t\t}\n \t\t}\ndiff --git a/net/sctp/sm_statefuns.c b/net/sctp/sm_statefuns.c\nindex d23d935e128e96..89ed618b1de30f 100644\n--- a/net/sctp/sm_statefuns.c\n+++ b/net/sctp/sm_statefuns.c\n@@ -642,7 +642,7 @@ static bool sctp_auth_chunk_verify(struct net *net, struct sctp_chunk *chunk,\n \tstruct sctp_chunk auth;\n \n \tif (!chunk-\u003eauth_chunk)\n-\t\treturn true;\n+\t\treturn !sctp_auth_recv_cid(chunk-\u003echunk_hdr-\u003etype, asoc);\n \n \t/* SCTP-AUTH:  auth_chunk pointer is only set when the cookie-echo\n \t * is supposed to be authenticated and we have to do delayed\n"
}

gemini-3.1-pro-preview

null

{
  "EnableConfigs": [
    "IP_SCTP"
  ],
  "FocusSymbols": [
    "sctp_assoc_bh_rcv",
    "sctp_endpoint_bh_rcv",
    "sctp_auth_chunk_verify"
  ],
  "Reasoning": "The patch fixes a potential NULL pointer dereference when skb_clone fails during SCTP chunk authentication. It modifies core SCTP receive path logic, which is reachable and functional.",
  "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 6b3917e93b4d22e1b1acf3be73c0c0d6f7852bce
Author: syz-cluster <triage@syzkaller.com>
Date:   Mon Jul 20 13:32:21 2026 +0000

    syz-cluster: applied patch under review

diff --git a/net/sctp/associola.c b/net/sctp/associola.c
index 62d3cc155809c7..e540683053960e 100644
--- a/net/sctp/associola.c
+++ b/net/sctp/associola.c
@@ -999,7 +999,8 @@ static void sctp_assoc_bh_rcv(struct work_struct *work)
 			if (next_hdr->type == SCTP_CID_COOKIE_ECHO) {
 				chunk->auth_chunk = skb_clone(chunk->skb,
 							      GFP_ATOMIC);
-				chunk->auth = 1;
+				if (chunk->auth_chunk)
+					chunk->auth = 1;
 				continue;
 			}
 		}
diff --git a/net/sctp/endpointola.c b/net/sctp/endpointola.c
index dfb1719275dba7..3419748c66bc14 100644
--- a/net/sctp/endpointola.c
+++ b/net/sctp/endpointola.c
@@ -368,7 +368,8 @@ static void sctp_endpoint_bh_rcv(struct work_struct *work)
 			if (next_hdr->type == SCTP_CID_COOKIE_ECHO) {
 				chunk->auth_chunk = skb_clone(chunk->skb,
 								GFP_ATOMIC);
-				chunk->auth = 1;
+				if (chunk->auth_chunk)
+					chunk->auth = 1;
 				continue;
 			}
 		}
diff --git a/net/sctp/sm_statefuns.c b/net/sctp/sm_statefuns.c
index d23d935e128e96..89ed618b1de30f 100644
--- a/net/sctp/sm_statefuns.c
+++ b/net/sctp/sm_statefuns.c
@@ -642,7 +642,7 @@ static bool sctp_auth_chunk_verify(struct net *net, struct sctp_chunk *chunk,
 	struct sctp_chunk auth;
 
 	if (!chunk->auth_chunk)
-		return true;
+		return !sctp_auth_recv_cid(chunk->chunk_hdr->type, asoc);
 
 	/* SCTP-AUTH:  auth_chunk pointer is only set when the cookie-echo
 	 * is supposed to be authenticated and we have to do delayed

gemini-3.1-pro-preview

null

null

							input: 2305
							output: 34
							thoughts: 174
						

**SCTP Patch Review**

Okay, so I've been looking at this patch and it seems to touch some critical authentication logic within the SCTP stack, specifically in `net/sctp/associola.c`, `net/sctp/endpointola.c`, and `net/sctp/sm_statefuns.c`. The core of the change appears to be focused on ensuring the integrity of the cloned skb. I can see they're verifying the return of `skb_clone` before setting `chunk->auth = 1`. That’s a good defensive programming approach; avoiding null dereference is always a win.

Also, it looks like they've modified the behavior of `sctp_auth_chunk_verify`. The original logic might have been overly permissive, but now it seems that the check `!chunk->auth_chunk` will return the inverse of the `sctp_auth_recv_cid` call, which is sensible. A proper authentication check should return false when a non-authentication chunk type is present. The original code could have passed authentication to an unauthorized chunk, so this patch is a step in the right direction. I should check the context of this call to be sure that this change is safe.

Before I go any further, I'll quickly check the relevant configuration options. Naturally, `IP_SCTP` will be the primary one. I'll need to make sure I understand all the dependencies and conditional compilation involved before I sign off on this. Let me quickly scan for any other SCTP-related configs to see what might influence this change. It would be valuable to understand how this patch interacts with other security features.

{
  "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: 2936
							output: 107
							thoughts: 70
						

**Analyzing the SCTP Implementation**

Okay, so the primary configuration we're dealing with here is `IP_SCTP`. My immediate thought is to zero in on the functions that have been touched related to that. Specifically, I need to see what's changed within `sctp_assoc_bh_rcv`, `sctp_endpoint_bh_rcv`, and `sctp_auth_chunk_verify`. Those are the usual suspects when we're talking about SCTP packet handling and authentication, which would be impacted by protocol-level configuration changes. I need to get a really good handle on *how* they've been modified.

Now, before I dig in too deeply, I should also make sure I'm not missing anything. I need to make sure I haven't missed any other configuration dependencies. There's almost always something related to security that needs a double-check. Time to verify if there any other relevant configurations that have also been changed.

{
  "Expression": "sctp_assoc_bh_rcv",
  "PathPrefix": "net/sctp/"
}

{
  "Output": "net/sctp/associola.c=43=static void sctp_select_active_and_retran_path(struct sctp_association *asoc);\nnet/sctp/associola.c:44:static void sctp_assoc_bh_rcv(struct work_struct *work);\nnet/sctp/associola.c-45-static void sctp_assoc_free_asconf_acks(struct sctp_association *asoc);\n--\nnet/sctp/associola.c=51=static struct sctp_association *sctp_association_init(\n--\nnet/sctp/associola.c-224-\tsctp_inq_init(\u0026asoc-\u003ebase.inqueue);\nnet/sctp/associola.c:225:\tsctp_inq_set_th_handler(\u0026asoc-\u003ebase.inqueue, sctp_assoc_bh_rcv);\nnet/sctp/associola.c-226-\n--\nnet/sctp/associola.c=905=struct sctp_transport *sctp_assoc_lookup_tsn(struct sctp_association *asoc,\n--\nnet/sctp/associola.c-960-/* Do delayed input processing.  This is scheduled by sctp_rcv(). */\nnet/sctp/associola.c:961:static void sctp_assoc_bh_rcv(struct work_struct *work)\nnet/sctp/associola.c-962-{\n"
}

{
  "Expression": "sctp_endpoint_bh_rcv",
  "PathPrefix": "net/sctp/"
}

{
  "Output": "net/sctp/endpointola.c-35-/* Forward declarations for internal helpers. */\nnet/sctp/endpointola.c:36:static void sctp_endpoint_bh_rcv(struct work_struct *work);\nnet/sctp/endpointola.c-37-\n--\nnet/sctp/endpointola.c=50=static struct sctp_endpoint *sctp_endpoint_init(struct sctp_endpoint *ep,\n--\nnet/sctp/endpointola.c-79-\t/* Set its top-half handler */\nnet/sctp/endpointola.c:80:\tsctp_inq_set_th_handler(\u0026ep-\u003ebase.inqueue, sctp_endpoint_bh_rcv);\nnet/sctp/endpointola.c-81-\n--\nnet/sctp/endpointola.c=302=bool sctp_endpoint_is_peeled_off(struct sctp_endpoint *ep,\n--\nnet/sctp/endpointola.c-325- */\nnet/sctp/endpointola.c:326:static void sctp_endpoint_bh_rcv(struct work_struct *work)\nnet/sctp/endpointola.c-327-{\n"
}

{
  "Expression": "sctp_auth_chunk_verify",
  "PathPrefix": "net/sctp/"
}

{
  "Output": "net/sctp/sm_statefuns.c=520=enum sctp_disposition sctp_sf_do_5_1C_ack(struct net *net,\n--\nnet/sctp/sm_statefuns.c-638-\nnet/sctp/sm_statefuns.c:639:static bool sctp_auth_chunk_verify(struct net *net, struct sctp_chunk *chunk,\nnet/sctp/sm_statefuns.c-640-\t\t\t\t   const struct sctp_association *asoc)\n--\nnet/sctp/sm_statefuns.c=702=enum sctp_disposition sctp_sf_do_5_1D_ce(struct net *net,\n--\nnet/sctp/sm_statefuns.c-827-\nnet/sctp/sm_statefuns.c:828:\tif (!sctp_auth_chunk_verify(net, chunk, new_asoc)) {\nnet/sctp/sm_statefuns.c-829-\t\tsctp_association_free(new_asoc);\n--\nnet/sctp/sm_statefuns.c=1881=static enum sctp_disposition sctp_sf_do_dupcook_a(\n--\nnet/sctp/sm_statefuns.c-1905-\nnet/sctp/sm_statefuns.c:1906:\tif (!sctp_auth_chunk_verify(net, chunk, new_asoc))\nnet/sctp/sm_statefuns.c-1907-\t\treturn SCTP_DISPOSITION_DISCARD;\n--\nnet/sctp/sm_statefuns.c=2004=static enum sctp_disposition sctp_sf_do_dupcook_b(\n--\nnet/sctp/sm_statefuns.c-2025-\nnet/sctp/sm_statefuns.c:2026:\tif (!sctp_auth_chunk_verify(net, chunk, new_asoc))\nnet/sctp/sm_statefuns.c-2027-\t\treturn SCTP_DISPOSITION_DISCARD;\n--\nnet/sctp/sm_statefuns.c=2111=static enum sctp_disposition sctp_sf_do_dupcook_d(\n--\nnet/sctp/sm_statefuns.c-2128-\nnet/sctp/sm_statefuns.c:2129:\tif (!sctp_auth_chunk_verify(net, chunk, asoc))\nnet/sctp/sm_statefuns.c-2130-\t\treturn SCTP_DISPOSITION_DISCARD;\n"
}

gemini-3.1-pro-preview

null

null

							input: 4758
							output: 31
							thoughts: 157
						

**Analyzing a Potential Security Vulnerability Fix**

Okay, so I'm looking at this patch and immediately, I can see it addresses a critical issue related to SCTP handling. The core of the problem seems to be that `skb_clone` can return NULL, yet the `chunk->auth` flag is being set regardless, which is a textbook recipe for a crash or some really nasty, unpredictable behavior. That's a definite red flag. The patch itself directly addresses this by modifying `sctp_auth_chunk_verify` to perform a check on `sctp_auth_recv_cid` if `chunk->auth_chunk` is NULL. This is a solid, targeted approach.

From a functional perspective, I am confident this is reachable. The patch directly touches critical components. My mental checklist says the relevant config is `IP_SCTP`, which I would expect. Now, to zero in on the key functions, my initial focus symbols are: `sctp_assoc_bh_rcv`, `sctp_endpoint_bh_rcv`, and of course, `sctp_auth_chunk_verify`. These functions are going to be where I need to dig in to confirm the impact and ensure the fix is complete. I also have to check if there are any specific configs for `SCTP_AUTH` that might further clarify things. I need to make sure this doesn't introduce any regressions or unintended consequences, so I'll need to evaluate the changes against the existing code base.

no matches

{
  "Expression": "config SCTP_AUTH",
  "PathPrefix": "net/sctp/"
}

{
  "error": "no matches"
}

gemini-3.1-pro-preview

null

null

							input: 5282
							output: 30
							thoughts: 43
						

Okay, here's my interpretation of those thoughts, speaking as an expert:

**SCTP Authentication Conundrum**

Alright, so I'm digging into this SCTP implementation, and it seems there's no explicit configuration option for `SCTP_AUTH` as a module parameter or anything similar. That's a bit odd. My initial assumption is that it's either baked in by default, always enabled, or perhaps it's entirely managed through those good old `sysctl` knobs, which would make sense from a design standpoint. Keeps it more flexible, you know?

Let's not jump to conclusions though; I should really make sure there isn't some obscure config buried elsewhere. Time to crack open `net/sctp/Kconfig` and see if there are any other related kernel configuration options in there that might shed some light on this authentication behavior. Gotta be thorough.

{
  "Expression": "config ",
  "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--\nnet/sctp/Kconfig=39=if IP_SCTP\nnet/sctp/Kconfig-40-\nnet/sctp/Kconfig:41:config SCTP_DBG_OBJCNT\nnet/sctp/Kconfig-42-\tbool \"SCTP: Debug object counts\"\n--\nnet/sctp/Kconfig=52=choice\n--\nnet/sctp/Kconfig-61-\nnet/sctp/Kconfig:62:config SCTP_DEFAULT_COOKIE_HMAC_SHA256\nnet/sctp/Kconfig-63-\tbool \"HMAC-SHA256\"\nnet/sctp/Kconfig-64-\nnet/sctp/Kconfig:65:config SCTP_DEFAULT_COOKIE_HMAC_NONE\nnet/sctp/Kconfig-66-\tbool \"None\"\n--\nnet/sctp/Kconfig=68=endchoice\nnet/sctp/Kconfig-69-\nnet/sctp/Kconfig:70:config INET_SCTP_DIAG\nnet/sctp/Kconfig-71-\tdepends on INET_DIAG\n"
}

gemini-3.1-pro-preview

null

null

							input: 5903
							output: 111
							thoughts: 189
						

**Fuzzing Focus: Refined Target Identification**

Okay, so it looks like `IP_SCTP` is the crucial focus here, that simplifies things. Now, let's take a closer look at these target symbols: `sctp_assoc_bh_rcv`, `sctp_endpoint_bh_rcv`, and `sctp_auth_chunk_verify`. Unlike the more general entry points like `sctp_rcv` or `ip_rcv`, these seem highly relevant to association, endpoint receive processing (in the bottom half of the stack), and authentication chunk verification specifically within SCTP. This is good, a more targeted attack surface is ideal.

Next, I need to verify a detail. Are those functions, especially `sctp_auth_chunk_verify`, static? A quick check... yep, and `sctp_assoc_bh_rcv`, as well as `sctp_endpoint_bh_rcv` are also static. Perfect. They are exactly the functions that are under scrutiny in my modifications. Static functions are ideal fuzzing targets.

Alright, that settles it. Time to record these findings and set the results accordingly.

{
  "EnableConfigs": [
    "IP_SCTP"
  ],
  "FocusSymbols": [
    "sctp_assoc_bh_rcv",
    "sctp_endpoint_bh_rcv",
    "sctp_auth_chunk_verify"
  ],
  "Reasoning": "The patch fixes a potential NULL pointer dereference when skb_clone fails during SCTP chunk authentication. It modifies core SCTP receive path logic, which is reachable and functional.",
  "WorthFuzzing": true
}

{
  "EnableConfigs": [
    "IP_SCTP"
  ],
  "FocusSymbols": [
    "sctp_assoc_bh_rcv",
    "sctp_endpoint_bh_rcv",
    "sctp_auth_chunk_verify"
  ],
  "Reasoning": "The patch fixes a potential NULL pointer dereference when skb_clone fails during SCTP chunk authentication. It modifies core SCTP receive path logic, which is reachable and functional.",
  "WorthFuzzing": true
}