AI Trajectory

null

{
  "EnableConfigs": [
    "IP_SCTP",
    "SCTP_DEFAULT_COOKIE_HMAC_NONE"
  ],
  "FocusSymbols": [
    "sctp_unpack_cookie",
    "sctp_verify_init",
    "sctp_sf_do_5_1D_ce",
    "sctp_sf_do_5_2_4_dupcook"
  ],
  "Reasoning": "The patch modifies SCTP chunk processing and validation logic, specifically for COOKIE ECHO and INIT chunks. It adds new checks to prevent malformed chunks from being processed and adds verification steps during association establishment. These are functional changes in the core SCTP state machine and should be fuzzed.",
  "WorthFuzzing": true
}

null

{
  "PatchDiff": "commit acd6825e98d1fc71d7e99e9e89dc6ba319435d76\nAuthor: syz-cluster \u003ctriage@syzkaller.com\u003e\nDate:   Wed Jun 24 23:30:23 2026 +0000\n\n    syz-cluster: applied patch under review\n\ndiff --git a/net/sctp/sm_make_chunk.c b/net/sctp/sm_make_chunk.c\nindex 41958b8e59fd53..8adac9e0cd66be 100644\n--- a/net/sctp/sm_make_chunk.c\n+++ b/net/sctp/sm_make_chunk.c\n@@ -1761,6 +1761,8 @@ struct sctp_association *sctp_unpack_cookie(\n \tbear_cookie = \u0026cookie-\u003ec;\n \n \tch = (struct sctp_chunkhdr *)(bear_cookie + 1);\n+\tif (ch-\u003etype != SCTP_CID_INIT)\n+\t\tgoto malformed;\n \tchlen = ntohs(ch-\u003elength);\n \tif (chlen \u003c sizeof(struct sctp_init_chunk))\n \t\tgoto malformed;\n@@ -2298,7 +2300,8 @@ int sctp_verify_init(struct net *net, const struct sctp_endpoint *ep,\n \t * VIOLATION error.  We build the ERROR chunk here and let the normal\n \t * error handling code build and send the packet.\n \t */\n-\tif (param.v != (void *)chunk-\u003echunk_end)\n+\tif (param.v != (void *)peer_init +\n+\t\t       SCTP_PAD4(ntohs(peer_init-\u003echunk_hdr.length)))\n \t\treturn sctp_process_inv_paramlength(asoc, param.p, chunk, errp);\n \n \t/* The only missing mandatory param possible today is\ndiff --git a/net/sctp/sm_statefuns.c b/net/sctp/sm_statefuns.c\nindex 8e920cef0858cf..d23d935e128e96 100644\n--- a/net/sctp/sm_statefuns.c\n+++ b/net/sctp/sm_statefuns.c\n@@ -707,11 +707,12 @@ enum sctp_disposition sctp_sf_do_5_1D_ce(struct net *net,\n \t\t\t\t\t struct sctp_cmd_seq *commands)\n {\n \tstruct sctp_ulpevent *ev, *ai_ev = NULL, *auth_ev = NULL;\n+\tstruct sctp_chunk *err_chk_p = NULL;\n \tstruct sctp_association *new_asoc;\n \tstruct sctp_init_chunk *peer_init;\n \tstruct sctp_chunk *chunk = arg;\n-\tstruct sctp_chunk *err_chk_p;\n \tstruct sctp_chunk *repl;\n+\tenum sctp_cid cid;\n \tstruct sock *sk;\n \tint error = 0;\n \n@@ -785,6 +786,19 @@ enum sctp_disposition sctp_sf_do_5_1D_ce(struct net *net,\n \t\t}\n \t}\n \n+\tpeer_init = (struct sctp_init_chunk *)(chunk-\u003esubh.cookie_hdr + 1);\n+\tcid = peer_init-\u003echunk_hdr.type;\n+\tif (!sctp_sk(sk)-\u003ecookie_auth_enable \u0026\u0026\n+\t    !sctp_verify_init(net, ep, asoc, cid, peer_init, chunk,\n+\t\t\t      \u0026err_chk_p)) {\n+\t\tsctp_association_free(new_asoc);\n+\t\tif (err_chk_p)\n+\t\t\tsctp_chunk_free(err_chk_p);\n+\t\treturn sctp_sf_pdiscard(net, ep, asoc, type, arg, commands);\n+\t}\n+\tif (err_chk_p)\n+\t\tsctp_chunk_free(err_chk_p);\n+\n \tif (security_sctp_assoc_request(new_asoc, chunk-\u003ehead_skb ?: chunk-\u003eskb)) {\n \t\tsctp_association_free(new_asoc);\n \t\treturn sctp_sf_pdiscard(net, ep, asoc, type, arg, commands);\n@@ -798,7 +812,6 @@ enum sctp_disposition sctp_sf_do_5_1D_ce(struct net *net,\n \t/* This is a brand-new association, so these are not yet side\n \t * effects--it is safe to run them here.\n \t */\n-\tpeer_init = (struct sctp_init_chunk *)(chunk-\u003esubh.cookie_hdr + 1);\n \tif (!sctp_process_init(new_asoc, chunk,\n \t\t\t       \u0026chunk-\u003esubh.cookie_hdr-\u003ec.peer_addr,\n \t\t\t       peer_init, GFP_ATOMIC))\n@@ -2215,10 +2228,12 @@ enum sctp_disposition sctp_sf_do_5_2_4_dupcook(\n \t\t\t\t\tvoid *arg,\n \t\t\t\t\tstruct sctp_cmd_seq *commands)\n {\n+\tstruct sctp_chunk *err_chk_p = NULL;\n \tstruct sctp_association *new_asoc;\n+\tstruct sctp_init_chunk *peer_init;\n \tstruct sctp_chunk *chunk = arg;\n \tenum sctp_disposition retval;\n-\tstruct sctp_chunk *err_chk_p;\n+\tenum sctp_cid cid;\n \tint error = 0;\n \tchar action;\n \n@@ -2287,6 +2302,21 @@ enum sctp_disposition sctp_sf_do_5_2_4_dupcook(\n \tswitch (action) {\n \tcase 'A': /* Association restart. */\n \tcase 'B': /* Collision case B. */\n+\t\tpeer_init = (struct sctp_init_chunk *)\n+\t\t\t\t(chunk-\u003esubh.cookie_hdr + 1);\n+\t\tcid = peer_init-\u003echunk_hdr.type;\n+\t\tif (!sctp_sk(ep-\u003ebase.sk)-\u003ecookie_auth_enable \u0026\u0026\n+\t\t    !sctp_verify_init(net, ep, asoc, cid, peer_init, chunk,\n+\t\t\t\t      \u0026err_chk_p)) {\n+\t\t\tsctp_association_free(new_asoc);\n+\t\t\tif (err_chk_p)\n+\t\t\t\tsctp_chunk_free(err_chk_p);\n+\t\t\treturn sctp_sf_pdiscard(net, ep, asoc, type, arg,\n+\t\t\t\t\t\tcommands);\n+\t\t}\n+\t\tif (err_chk_p)\n+\t\t\tsctp_chunk_free(err_chk_p);\n+\t\tfallthrough;\n \tcase 'D': /* Collision case D. */\n \t\t/* Update socket peer label if first association. */\n \t\tif (security_sctp_assoc_request((struct sctp_association *)asoc,\n"
}

gemini-3.1-pro-preview

null

{
  "EnableConfigs": [
    "IP_SCTP",
    "SCTP_DEFAULT_COOKIE_HMAC_NONE"
  ],
  "FocusSymbols": [
    "sctp_unpack_cookie",
    "sctp_verify_init",
    "sctp_sf_do_5_1D_ce",
    "sctp_sf_do_5_2_4_dupcook"
  ],
  "Reasoning": "The patch modifies SCTP chunk processing and validation logic, specifically for COOKIE ECHO and INIT chunks. It adds new checks to prevent malformed chunks from being processed and adds verification steps during association establishment. These are functional changes in the core SCTP state machine 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 acd6825e98d1fc71d7e99e9e89dc6ba319435d76
Author: syz-cluster <triage@syzkaller.com>
Date:   Wed Jun 24 23:30:23 2026 +0000

    syz-cluster: applied patch under review

diff --git a/net/sctp/sm_make_chunk.c b/net/sctp/sm_make_chunk.c
index 41958b8e59fd53..8adac9e0cd66be 100644
--- a/net/sctp/sm_make_chunk.c
+++ b/net/sctp/sm_make_chunk.c
@@ -1761,6 +1761,8 @@ struct sctp_association *sctp_unpack_cookie(
 	bear_cookie = &cookie->c;
 
 	ch = (struct sctp_chunkhdr *)(bear_cookie + 1);
+	if (ch->type != SCTP_CID_INIT)
+		goto malformed;
 	chlen = ntohs(ch->length);
 	if (chlen < sizeof(struct sctp_init_chunk))
 		goto malformed;
@@ -2298,7 +2300,8 @@ int sctp_verify_init(struct net *net, const struct sctp_endpoint *ep,
 	 * VIOLATION error.  We build the ERROR chunk here and let the normal
 	 * error handling code build and send the packet.
 	 */
-	if (param.v != (void *)chunk->chunk_end)
+	if (param.v != (void *)peer_init +
+		       SCTP_PAD4(ntohs(peer_init->chunk_hdr.length)))
 		return sctp_process_inv_paramlength(asoc, param.p, chunk, errp);
 
 	/* The only missing mandatory param possible today is
diff --git a/net/sctp/sm_statefuns.c b/net/sctp/sm_statefuns.c
index 8e920cef0858cf..d23d935e128e96 100644
--- a/net/sctp/sm_statefuns.c
+++ b/net/sctp/sm_statefuns.c
@@ -707,11 +707,12 @@ enum sctp_disposition sctp_sf_do_5_1D_ce(struct net *net,
 					 struct sctp_cmd_seq *commands)
 {
 	struct sctp_ulpevent *ev, *ai_ev = NULL, *auth_ev = NULL;
+	struct sctp_chunk *err_chk_p = NULL;
 	struct sctp_association *new_asoc;
 	struct sctp_init_chunk *peer_init;
 	struct sctp_chunk *chunk = arg;
-	struct sctp_chunk *err_chk_p;
 	struct sctp_chunk *repl;
+	enum sctp_cid cid;
 	struct sock *sk;
 	int error = 0;
 
@@ -785,6 +786,19 @@ enum sctp_disposition sctp_sf_do_5_1D_ce(struct net *net,
 		}
 	}
 
+	peer_init = (struct sctp_init_chunk *)(chunk->subh.cookie_hdr + 1);
+	cid = peer_init->chunk_hdr.type;
+	if (!sctp_sk(sk)->cookie_auth_enable &&
+	    !sctp_verify_init(net, ep, asoc, cid, peer_init, chunk,
+			      &err_chk_p)) {
+		sctp_association_free(new_asoc);
+		if (err_chk_p)
+			sctp_chunk_free(err_chk_p);
+		return sctp_sf_pdiscard(net, ep, asoc, type, arg, commands);
+	}
+	if (err_chk_p)
+		sctp_chunk_free(err_chk_p);
+
 	if (security_sctp_assoc_request(new_asoc, chunk->head_skb ?: chunk->skb)) {
 		sctp_association_free(new_asoc);
 		return sctp_sf_pdiscard(net, ep, asoc, type, arg, commands);
@@ -798,7 +812,6 @@ enum sctp_disposition sctp_sf_do_5_1D_ce(struct net *net,
 	/* This is a brand-new association, so these are not yet side
 	 * effects--it is safe to run them here.
 	 */
-	peer_init = (struct sctp_init_chunk *)(chunk->subh.cookie_hdr + 1);
 	if (!sctp_process_init(new_asoc, chunk,
 			       &chunk->subh.cookie_hdr->c.peer_addr,
 			       peer_init, GFP_ATOMIC))
@@ -2215,10 +2228,12 @@ enum sctp_disposition sctp_sf_do_5_2_4_dupcook(
 					void *arg,
 					struct sctp_cmd_seq *commands)
 {
+	struct sctp_chunk *err_chk_p = NULL;
 	struct sctp_association *new_asoc;
+	struct sctp_init_chunk *peer_init;
 	struct sctp_chunk *chunk = arg;
 	enum sctp_disposition retval;
-	struct sctp_chunk *err_chk_p;
+	enum sctp_cid cid;
 	int error = 0;
 	char action;
 
@@ -2287,6 +2302,21 @@ enum sctp_disposition sctp_sf_do_5_2_4_dupcook(
 	switch (action) {
 	case 'A': /* Association restart. */
 	case 'B': /* Collision case B. */
+		peer_init = (struct sctp_init_chunk *)
+				(chunk->subh.cookie_hdr + 1);
+		cid = peer_init->chunk_hdr.type;
+		if (!sctp_sk(ep->base.sk)->cookie_auth_enable &&
+		    !sctp_verify_init(net, ep, asoc, cid, peer_init, chunk,
+				      &err_chk_p)) {
+			sctp_association_free(new_asoc);
+			if (err_chk_p)
+				sctp_chunk_free(err_chk_p);
+			return sctp_sf_pdiscard(net, ep, asoc, type, arg,
+						commands);
+		}
+		if (err_chk_p)
+			sctp_chunk_free(err_chk_p);
+		fallthrough;
 	case 'D': /* Collision case D. */
 		/* Update socket peer label if first association. */
 		if (security_sctp_assoc_request((struct sctp_association *)asoc,

gemini-3.1-pro-preview

null

null

							input: 3375
							output: 32
							thoughts: 234
						

**Fuzzing Target Identification: SCTP Patch Analysis**

Okay, so I've got a patch here that's poking around in the SCTP implementation, specifically `net/sctp/sm_make_chunk.c` and `net/sctp/sm_statefuns.c`. The changes seem to center around `sctp_verify_init` and a check for `ch->type != SCTP_CID_INIT`. Right off the bat, this screams potential fuzzing target to me. It's touching core SCTP functionality, so any unexpected behavior there could be interesting.

Now, I need to pinpoint the exact functions that have been modified. Looks like in `sm_make_chunk.c`, it's `sctp_unpack_cookie` and `sctp_verify_init`. Then, in `sm_statefuns.c`, the patch affects `sctp_sf_do_5_1D_ce` and `sctp_sf_do_5_2_4_dupcook`. That's a solid list to keep in mind.

To make sure I'm targeting the right code, I'll need to check the Kconfig settings. I already know that `IP_SCTP` is the main config option for SCTP, but I need to be absolutely certain of the exact Kconfig name to use for building the fuzzing environment. I'll fire up `grepper` and double-check to nail down the exact configuration setting for the fuzzer.

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

{
  "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: 4038
							output: 40
							thoughts: 73
						

Okay, let's break this down.

**Investigating the `IP_SCTP` Configuration and Related Code**

Right, so the core configuration point we're dealing with is `IP_SCTP`. My first thought is always to confirm that this is the only relevant piece and if there are any other settings that might be dependent on it, which could affect its behavior or how it interacts with the rest of the stack.

I need to dig into the implementation, and I know from experience that the main logic often resides in `net/sctp/sm_make_chunk.c` and `net/sctp/sm_statefuns.c`. Those seem like the logical places to start poking around. I'll need to look very closely, because the code might not be obviously impacted by the config.

My next step will be to search for any conditional compilation `#ifdef` directives around the code I'm looking at. I'll need to determine the extent of its influence and how the code changes depending on the configuration. Any use of `#ifdef IP_SCTP` is what I'm focused on, and if it's there I'll be able to tell how it is impacted and if it's the only impact.

{
  "Expression": "sctp_sf_do_5_1D_ce",
  "PathPrefix": "net/sctp/"
}

{
  "Output": "net/sctp/sm_statefuns.c=639=static bool sctp_auth_chunk_verify(struct net *net, struct sctp_chunk *chunk,\n--\nnet/sctp/sm_statefuns.c-701- */\nnet/sctp/sm_statefuns.c:702:enum sctp_disposition sctp_sf_do_5_1D_ce(struct net *net,\nnet/sctp/sm_statefuns.c-703-\t\t\t\t\t const struct sctp_endpoint *ep,\n--\nnet/sctp/sm_statetable.c=65=const struct sctp_sm_table_entry *sctp_sm_lookup_event(\n--\nnet/sctp/sm_statetable.c-283-\t/* SCTP_STATE_CLOSED */ \\\nnet/sctp/sm_statetable.c:284:\tTYPE_SCTP_FUNC(sctp_sf_do_5_1D_ce), \\\nnet/sctp/sm_statetable.c-285-\t/* SCTP_STATE_COOKIE_WAIT */ \\\n"
}

gemini-3.1-pro-preview

null

null

							input: 4717
							output: 31
							thoughts: 285
						

**Analyzing SCTP Core Functions for Focus**

Okay, let's break this down. My focus right now is on understanding the modifications to these specific SCTP functions: `sctp_unpack_cookie`, `sctp_verify_init`, `sctp_sf_do_5_1D_ce`, and `sctp_sf_do_5_2_4_dupcook`. We know these are deep inside the SCTP state machine and crucial for chunk processing. They’re activated when SCTP is enabled, as we'd expect, controlled by `CONFIG_IP_SCTP`.

I need to confirm whether `sctp_sf_do_5_1D_ce` and `sctp_sf_do_5_2_4_dupcook` are truly "hot path" functions. They handle COOKIE ECHO and duplicate COOKIE ECHO chunks respectively. These are primarily involved during the initial association setup, that handshake process, so they're not going to be handling every data packet like your standard data chunk processing would. Still, they are relatively common during connection establishment, and they’re specific enough to be considered good focus symbols. So that's the angle I'm taking. The other two, `sctp_unpack_cookie` and `sctp_verify_init`, also seem like solid targets for in-depth examination.

Now, let's dig a bit deeper into the configuration side. I see a check related to `cookie_auth_enable` in the patch: `!sctp_sk(sk)->cookie_auth_enable`. I'm going to look for the configuration option that's linked to this. It's important to understand how this is controlled.

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

{
  "Output": "net/sctp/protocol.c=1288=static int __net_init sctp_defaults_init(struct net *net)\n--\nnet/sctp/protocol.c-1313-\t/* Whether cookie authentication is enabled(1) or not(0) */\nnet/sctp/protocol.c:1314:\tnet-\u003esctp.cookie_auth_enable =\nnet/sctp/protocol.c-1315-\t\t!IS_ENABLED(CONFIG_SCTP_DEFAULT_COOKIE_HMAC_NONE);\n--\nnet/sctp/sm_make_chunk.c=1645=static struct sctp_cookie_param *sctp_pack_cookie(\n--\nnet/sctp/sm_make_chunk.c-1711-\t/* Sign the cookie, if cookie authentication is enabled. */\nnet/sctp/sm_make_chunk.c:1712:\tif (sctp_sk(ep-\u003ebase.sk)-\u003ecookie_auth_enable) {\nnet/sctp/sm_make_chunk.c-1713-\t\tstatic_assert(sizeof(cookie-\u003emac) == SHA256_DIGEST_SIZE);\n--\nnet/sctp/sm_make_chunk.c=1722=struct sctp_association *sctp_unpack_cookie(\n--\nnet/sctp/sm_make_chunk.c-1774-\t/* Verify the cookie's MAC, if cookie authentication is enabled. */\nnet/sctp/sm_make_chunk.c:1775:\tif (sctp_sk(ep-\u003ebase.sk)-\u003ecookie_auth_enable) {\nnet/sctp/sm_make_chunk.c-1776-\t\tu8 mac[SHA256_DIGEST_SIZE];\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-790-\tcid = peer_init-\u003echunk_hdr.type;\nnet/sctp/sm_statefuns.c:791:\tif (!sctp_sk(sk)-\u003ecookie_auth_enable \u0026\u0026\nnet/sctp/sm_statefuns.c-792-\t    !sctp_verify_init(net, ep, asoc, cid, peer_init, chunk,\n--\nnet/sctp/sm_statefuns.c=2223=enum sctp_disposition sctp_sf_do_5_2_4_dupcook(\n--\nnet/sctp/sm_statefuns.c-2307-\t\tcid = peer_init-\u003echunk_hdr.type;\nnet/sctp/sm_statefuns.c:2308:\t\tif (!sctp_sk(ep-\u003ebase.sk)-\u003ecookie_auth_enable \u0026\u0026\nnet/sctp/sm_statefuns.c-2309-\t\t    !sctp_verify_init(net, ep, asoc, cid, peer_init, chunk,\n--\nnet/sctp/socket.c=5020=static int sctp_init_sock(struct sock *sk)\n--\nnet/sctp/socket.c-5054-\nnet/sctp/socket.c:5055:\tsp-\u003ecookie_auth_enable = net-\u003esctp.cookie_auth_enable;\nnet/sctp/socket.c-5056-\n--\nnet/sctp/sysctl.c=95=static struct ctl_table sctp_net_table[] = {\n--\nnet/sctp/sysctl.c-176-\t\t.procname\t= \"cookie_hmac_alg\",\nnet/sctp/sysctl.c:177:\t\t.data\t\t= \u0026init_net.sctp.cookie_auth_enable,\nnet/sctp/sysctl.c-178-\t\t.maxlen\t\t= 8,\n--\nnet/sctp/sysctl.c=387=static int proc_sctp_do_hmac_alg(const struct ctl_table *ctl, int write,\n--\nnet/sctp/sysctl.c-390-\tstruct net *net = container_of(ctl-\u003edata, struct net,\nnet/sctp/sysctl.c:391:\t\t\t\t       sctp.cookie_auth_enable);\nnet/sctp/sysctl.c-392-\tstruct ctl_table tbl;\n--\nnet/sctp/sysctl.c-404-\t\tif (!strcmp(tmp, \"sha256\")) {\nnet/sctp/sysctl.c:405:\t\t\tnet-\u003esctp.cookie_auth_enable = 1;\nnet/sctp/sysctl.c-406-\t\t\treturn 0;\n--\nnet/sctp/sysctl.c-408-\t\tif (!strcmp(tmp, \"none\")) {\nnet/sctp/sysctl.c:409:\t\t\tnet-\u003esctp.cookie_auth_enable = 0;\nnet/sctp/sysctl.c-410-\t\t\treturn 0;\n--\nnet/sctp/sysctl.c-413-\t}\nnet/sctp/sysctl.c:414:\tif (net-\u003esctp.cookie_auth_enable)\nnet/sctp/sysctl.c-415-\t\ttbl.data = (char *)\"sha256\";\n"
}

gemini-3.1-pro-preview

null

null

							input: 6807
							output: 38
							thoughts: 185
						

**Analyzing the `cookie_auth_enable` Logic**

Okay, let's break this down. It looks like the `cookie_auth_enable` flag is the key variable here. And it's directly tied to `CONFIG_SCTP_DEFAULT_COOKIE_HMAC_NONE`. If *that* is *not* enabled, `cookie_auth_enable` is set to 1. Got it. Now, the patch focuses on cases where we have `!sctp_sk(sk)->cookie_auth_enable`. This is the important part!

So, to actually trigger the new logic in `sctp_sf_do_5_1D_ce` and `sctp_sf_do_5_2_4_dupcook`, we need `cookie_auth_enable` to be 0. That's the condition that's being checked. This implies we need to make sure `CONFIG_SCTP_DEFAULT_COOKIE_HMAC_NONE` *is* enabled during the build. Alternatively, it can be adjusted via sysctl, which is less ideal for our purposes.

Right, so to confirm this, I need to double-check that `CONFIG_SCTP_DEFAULT_COOKIE_HMAC_NONE` is the correct name. Just to make sure my reasoning is spot on.

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

{
  "Output": "net/sctp/Kconfig=62=config SCTP_DEFAULT_COOKIE_HMAC_SHA256\n--\nnet/sctp/Kconfig-64-\nnet/sctp/Kconfig:65:config SCTP_DEFAULT_COOKIE_HMAC_NONE\nnet/sctp/Kconfig-66-\tbool \"None\"\n--\nnet/sctp/protocol.c=1288=static int __net_init sctp_defaults_init(struct net *net)\n--\nnet/sctp/protocol.c-1314-\tnet-\u003esctp.cookie_auth_enable =\nnet/sctp/protocol.c:1315:\t\t!IS_ENABLED(CONFIG_SCTP_DEFAULT_COOKIE_HMAC_NONE);\nnet/sctp/protocol.c-1316-\n"
}

gemini-3.1-pro-preview

null

null

							input: 7537
							output: 26
							thoughts: 523
						

**Analyzing the New SCTP Patch for Thorough Testing**

Okay, so I'm digging into this SCTP patch, and the configuration options are starting to make more sense. My initial thought was that `SCTP_DEFAULT_COOKIE_HMAC_NONE` was the key, but now I see it's more nuanced. If we enable `SCTP_DEFAULT_COOKIE_HMAC_NONE`, `cookie_auth_enable` defaults to 0, which means the new `sctp_verify_init` checks actually *run*.  If `cookie_auth_enable` is set to 1, those checks get skipped. So, while setting `SCTP_DEFAULT_COOKIE_HMAC_NONE` is beneficial for ensuring we hit the path, letting syzkaller set the sysctl is also a viable approach, but providing the config is definitely the safer option.

I quickly realized the more central config is `IP_SCTP`. Going deeper, I need to check `sctp_verify_init` in `net/sctp/sm_make_chunk.c`. The patch changes that code, and it appears the changes are *always* executed regardless of `cookie_auth_enable`'s value. Same story with `sctp_unpack_cookie`. The additional check within `sctp_unpack_cookie` is reached regardless of the authentication setting. That means the patch has functional changes that are reachable, which is exactly what I wanted to confirm.

So, the critical config to enable for testing is `IP_SCTP`, no question. Then, adding `SCTP_DEFAULT_COOKIE_HMAC_NONE` will guarantee that we reach the new code in `sctp_sf_do_5_1D_ce` and `sctp_sf_do_5_2_4_dupcook`.

Therefore, I think the focus symbols I need to target are:

*   `sctp_unpack_cookie`
*   `sctp_verify_init`
*   `sctp_sf_do_5_1D_ce`
*   `sctp_sf_do_5_2_4_dupcook`

These look good to me. They're not the super hot data transmission paths, which is fine, as they concern connection establishment and chunk validation. I am confident in my assessment, but will need to verify if there are any other configurations that could influence this code.

{
  "Expression": "config IP_SCTP",
  "PathPrefix": ""
}

{
  "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: 8686
							output: 35
							thoughts: 131
						

**Analyzing SCTP Cookie HMAC Configuration**

Alright, so I'm looking at `IP_SCTP` and specifically `SCTP_DEFAULT_COOKIE_HMAC_NONE`. I need to make absolutely sure I understand the implications of enabling this. My immediate thought is that it should disable HMAC for cookies by default, which is precisely the behavior I'm trying to achieve to trigger the `!sctp_sk(sk)->cookie_auth_enable` code path. Now, I need to verify that assumption. Therefore, I will check the `net/sctp/Kconfig` file. This should contain the relevant configuration details for `SCTP_DEFAULT_COOKIE_HMAC_NONE`.

{
  "File": "net/sctp/Kconfig",
  "FirstLine": 50,
  "LineCount": 50
}

{
  "Contents": "  50:\t\t  If unsure, say N\n  51:\t\n  52:\tchoice\n  53:\t\tprompt \"Default SCTP cookie authentication method\"\n  54:\t\tdefault SCTP_DEFAULT_COOKIE_HMAC_SHA256\n  55:\t\thelp\n  56:\t\t  This option sets the default SCTP cookie authentication method, for\n  57:\t\t  when a method hasn't been explicitly selected via the\n  58:\t\t  net.sctp.cookie_hmac_alg sysctl.\n  59:\t\n  60:\t\t  If unsure, choose the default (HMAC-SHA256).\n  61:\t\n  62:\tconfig SCTP_DEFAULT_COOKIE_HMAC_SHA256\n  63:\t\tbool \"HMAC-SHA256\"\n  64:\t\n  65:\tconfig SCTP_DEFAULT_COOKIE_HMAC_NONE\n  66:\t\tbool \"None\"\n  67:\t\n  68:\tendchoice\n  69:\t\n  70:\tconfig INET_SCTP_DIAG\n  71:\t\tdepends on INET_DIAG\n  72:\t\tdef_tristate INET_DIAG\n  73:\t\n  74:\t\n  75:\tendif # IP_SCTP\n"
}

gemini-3.1-pro-preview

null

null

							input: 9338
							output: 167
							thoughts: 203
						

**My Assessment of the SCTP Patch**

Okay, so I've confirmed that `SCTP_DEFAULT_COOKIE_HMAC_NONE` *is* a legitimate configuration option. Let's see, the relevant configs are `IP_SCTP` and `SCTP_DEFAULT_COOKIE_HMAC_NONE`.

This patch is digging into the heart of SCTP chunk handling and validation. We're specifically talking about COOKIE ECHO and INIT chunks, which are critical components of association establishment. The changes involve adding safeguards against malformed chunks – ensuring that the state machine doesn't get tripped up by garbage data – and implementing new verification steps during the establishment process.

Functionally, this means the core SCTP state machine is being tweaked. This is a red flag that demands rigorous fuzzing! I need to ensure that these changes don't introduce regressions or, even worse, create new vulnerabilities by mis-handling some of these edge cases. We need to hit this with everything we've got. Let's use `set-results` to keep track of this.

{
  "EnableConfigs": [
    "IP_SCTP",
    "SCTP_DEFAULT_COOKIE_HMAC_NONE"
  ],
  "FocusSymbols": [
    "sctp_unpack_cookie",
    "sctp_verify_init",
    "sctp_sf_do_5_1D_ce",
    "sctp_sf_do_5_2_4_dupcook"
  ],
  "Reasoning": "The patch modifies SCTP chunk processing and validation logic, specifically for COOKIE ECHO and INIT chunks. It adds new checks to prevent malformed chunks from being processed and adds verification steps during association establishment. These are functional changes in the core SCTP state machine and should be fuzzed.",
  "WorthFuzzing": true
}

{
  "EnableConfigs": [
    "IP_SCTP",
    "SCTP_DEFAULT_COOKIE_HMAC_NONE"
  ],
  "FocusSymbols": [
    "sctp_unpack_cookie",
    "sctp_verify_init",
    "sctp_sf_do_5_1D_ce",
    "sctp_sf_do_5_2_4_dupcook"
  ],
  "Reasoning": "The patch modifies SCTP chunk processing and validation logic, specifically for COOKIE ECHO and INIT chunks. It adds new checks to prevent malformed chunks from being processed and adds verification steps during association establishment. These are functional changes in the core SCTP state machine and should be fuzzed.",
  "WorthFuzzing": true
}