AI Trajectory

null

{
  "EnableConfigs": [
    "TIPC",
    "TIPC_MEDIA_UDP"
  ],
  "FocusSymbols": [
    "tipc_bcast_sync_rcv",
    "tipc_node_bc_sync_rcv"
  ],
  "Reasoning": "The patch adds validation for Gap ACK blocks in TIPC broadcast sync receive to prevent processing of malformed messages. This is a functional change in the network protocol handling that should be fuzzed to ensure the validation correctly handles malformed packets without causing regressions.",
  "WorthFuzzing": true
}

null

{
  "PatchDiff": "commit 600bf7aa58766c8b75c2a87bcb4587b7c86109b9\nAuthor: syz-cluster \u003ctriage@syzkaller.com\u003e\nDate:   Wed Jun 24 14:16:03 2026 +0000\n\n    syz-cluster: applied patch under review\n\ndiff --git a/net/tipc/bcast.c b/net/tipc/bcast.c\nindex 76a1585d3f6b6d..08637c3c9db0fb 100644\n--- a/net/tipc/bcast.c\n+++ b/net/tipc/bcast.c\n@@ -497,11 +497,12 @@ void tipc_bcast_ack_rcv(struct net *net, struct tipc_link *l,\n  */\n int tipc_bcast_sync_rcv(struct net *net, struct tipc_link *l,\n \t\t\tstruct tipc_msg *hdr,\n-\t\t\tstruct sk_buff_head *retrq)\n+\t\t\tstruct sk_buff_head *retrq, bool *valid)\n {\n \tstruct sk_buff_head *inputq = \u0026tipc_bc_base(net)-\u003einputq;\n \tstruct tipc_gap_ack_blks *ga;\n \tstruct sk_buff_head xmitq;\n+\tu16 glen;\n \tint rc = 0;\n \n \t__skb_queue_head_init(\u0026xmitq);\n@@ -510,13 +511,18 @@ int tipc_bcast_sync_rcv(struct net *net, struct tipc_link *l,\n \tif (msg_type(hdr) != STATE_MSG) {\n \t\ttipc_link_bc_init_rcv(l, hdr);\n \t} else if (!msg_bc_ack_invalid(hdr)) {\n-\t\ttipc_get_gap_ack_blks(\u0026ga, l, hdr, false);\n-\t\tif (!sysctl_tipc_bc_retruni)\n-\t\t\tretrq = \u0026xmitq;\n-\t\trc = tipc_link_bc_ack_rcv(l, msg_bcast_ack(hdr),\n-\t\t\t\t\t  msg_bc_gap(hdr), ga, \u0026xmitq,\n-\t\t\t\t\t  retrq);\n-\t\trc |= tipc_link_bc_sync_rcv(l, hdr, \u0026xmitq);\n+\t\tglen = tipc_get_gap_ack_blks(\u0026ga, l, hdr, false);\n+\t\tif (glen \u003e msg_data_sz(hdr)) {\n+\t\t\t/* Malformed Gap ACK blocks; caller drops the msg */\n+\t\t\t*valid = false;\n+\t\t} else {\n+\t\t\tif (!sysctl_tipc_bc_retruni)\n+\t\t\t\tretrq = \u0026xmitq;\n+\t\t\trc = tipc_link_bc_ack_rcv(l, msg_bcast_ack(hdr),\n+\t\t\t\t\t\t  msg_bc_gap(hdr), ga, \u0026xmitq,\n+\t\t\t\t\t\t  retrq);\n+\t\t\trc |= tipc_link_bc_sync_rcv(l, hdr, \u0026xmitq);\n+\t\t}\n \t}\n \ttipc_bcast_unlock(net);\n \ndiff --git a/net/tipc/bcast.h b/net/tipc/bcast.h\nindex 2d9352dc7b0e6e..55d17b5413e16b 100644\n--- a/net/tipc/bcast.h\n+++ b/net/tipc/bcast.h\n@@ -97,7 +97,7 @@ void tipc_bcast_ack_rcv(struct net *net, struct tipc_link *l,\n \t\t\tstruct tipc_msg *hdr);\n int tipc_bcast_sync_rcv(struct net *net, struct tipc_link *l,\n \t\t\tstruct tipc_msg *hdr,\n-\t\t\tstruct sk_buff_head *retrq);\n+\t\t\tstruct sk_buff_head *retrq, bool *valid);\n int tipc_nl_add_bc_link(struct net *net, struct tipc_nl_msg *msg,\n \t\t\tstruct tipc_link *bcl);\n int tipc_nl_bc_link_set(struct net *net, struct nlattr *attrs[]);\ndiff --git a/net/tipc/node.c b/net/tipc/node.c\nindex 97aa970a0d83ca..2887f94ee28faa 100644\n--- a/net/tipc/node.c\n+++ b/net/tipc/node.c\n@@ -1831,12 +1831,13 @@ static void tipc_node_mcast_rcv(struct tipc_node *n)\n }\n \n static void tipc_node_bc_sync_rcv(struct tipc_node *n, struct tipc_msg *hdr,\n-\t\t\t\t  int bearer_id, struct sk_buff_head *xmitq)\n+\t\t\t\t  int bearer_id, struct sk_buff_head *xmitq,\n+\t\t\t\t  bool *valid)\n {\n \tstruct tipc_link *ucl;\n \tint rc;\n \n-\trc = tipc_bcast_sync_rcv(n-\u003enet, n-\u003ebc_entry.link, hdr, xmitq);\n+\trc = tipc_bcast_sync_rcv(n-\u003enet, n-\u003ebc_entry.link, hdr, xmitq, valid);\n \n \tif (rc \u0026 TIPC_LINK_DOWN_EVT) {\n \t\ttipc_node_reset_links(n);\n@@ -2140,12 +2141,18 @@ void tipc_rcv(struct net *net, struct sk_buff *skb, struct tipc_bearer *b)\n \n \t/* Ensure broadcast reception is in synch with peer's send state */\n \tif (unlikely(usr == LINK_PROTOCOL)) {\n+\t\tbool valid = true;\n+\n \t\tif (unlikely(skb_linearize(skb))) {\n \t\t\ttipc_node_put(n);\n \t\t\tgoto discard;\n \t\t}\n \t\thdr = buf_msg(skb);\n-\t\ttipc_node_bc_sync_rcv(n, hdr, bearer_id, \u0026xmitq);\n+\t\ttipc_node_bc_sync_rcv(n, hdr, bearer_id, \u0026xmitq, \u0026valid);\n+\t\tif (!valid) {\n+\t\t\ttipc_node_put(n);\n+\t\t\tgoto discard;\n+\t\t}\n \t} else if (unlikely(tipc_link_acked(n-\u003ebc_entry.link) != bc_ack)) {\n \t\ttipc_bcast_ack_rcv(net, n-\u003ebc_entry.link, hdr);\n \t}\n"
}

gemini-3.1-pro-preview

null

{
  "EnableConfigs": [
    "TIPC",
    "TIPC_MEDIA_UDP"
  ],
  "FocusSymbols": [
    "tipc_bcast_sync_rcv",
    "tipc_node_bc_sync_rcv"
  ],
  "Reasoning": "The patch adds validation for Gap ACK blocks in TIPC broadcast sync receive to prevent processing of malformed messages. This is a functional change in the network protocol handling that should be fuzzed to ensure the validation correctly handles malformed packets without causing regressions.",
  "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 600bf7aa58766c8b75c2a87bcb4587b7c86109b9
Author: syz-cluster <triage@syzkaller.com>
Date:   Wed Jun 24 14:16:03 2026 +0000

    syz-cluster: applied patch under review

diff --git a/net/tipc/bcast.c b/net/tipc/bcast.c
index 76a1585d3f6b6d..08637c3c9db0fb 100644
--- a/net/tipc/bcast.c
+++ b/net/tipc/bcast.c
@@ -497,11 +497,12 @@ void tipc_bcast_ack_rcv(struct net *net, struct tipc_link *l,
  */
 int tipc_bcast_sync_rcv(struct net *net, struct tipc_link *l,
 			struct tipc_msg *hdr,
-			struct sk_buff_head *retrq)
+			struct sk_buff_head *retrq, bool *valid)
 {
 	struct sk_buff_head *inputq = &tipc_bc_base(net)->inputq;
 	struct tipc_gap_ack_blks *ga;
 	struct sk_buff_head xmitq;
+	u16 glen;
 	int rc = 0;
 
 	__skb_queue_head_init(&xmitq);
@@ -510,13 +511,18 @@ int tipc_bcast_sync_rcv(struct net *net, struct tipc_link *l,
 	if (msg_type(hdr) != STATE_MSG) {
 		tipc_link_bc_init_rcv(l, hdr);
 	} else if (!msg_bc_ack_invalid(hdr)) {
-		tipc_get_gap_ack_blks(&ga, l, hdr, false);
-		if (!sysctl_tipc_bc_retruni)
-			retrq = &xmitq;
-		rc = tipc_link_bc_ack_rcv(l, msg_bcast_ack(hdr),
-					  msg_bc_gap(hdr), ga, &xmitq,
-					  retrq);
-		rc |= tipc_link_bc_sync_rcv(l, hdr, &xmitq);
+		glen = tipc_get_gap_ack_blks(&ga, l, hdr, false);
+		if (glen > msg_data_sz(hdr)) {
+			/* Malformed Gap ACK blocks; caller drops the msg */
+			*valid = false;
+		} else {
+			if (!sysctl_tipc_bc_retruni)
+				retrq = &xmitq;
+			rc = tipc_link_bc_ack_rcv(l, msg_bcast_ack(hdr),
+						  msg_bc_gap(hdr), ga, &xmitq,
+						  retrq);
+			rc |= tipc_link_bc_sync_rcv(l, hdr, &xmitq);
+		}
 	}
 	tipc_bcast_unlock(net);
 
diff --git a/net/tipc/bcast.h b/net/tipc/bcast.h
index 2d9352dc7b0e6e..55d17b5413e16b 100644
--- a/net/tipc/bcast.h
+++ b/net/tipc/bcast.h
@@ -97,7 +97,7 @@ void tipc_bcast_ack_rcv(struct net *net, struct tipc_link *l,
 			struct tipc_msg *hdr);
 int tipc_bcast_sync_rcv(struct net *net, struct tipc_link *l,
 			struct tipc_msg *hdr,
-			struct sk_buff_head *retrq);
+			struct sk_buff_head *retrq, bool *valid);
 int tipc_nl_add_bc_link(struct net *net, struct tipc_nl_msg *msg,
 			struct tipc_link *bcl);
 int tipc_nl_bc_link_set(struct net *net, struct nlattr *attrs[]);
diff --git a/net/tipc/node.c b/net/tipc/node.c
index 97aa970a0d83ca..2887f94ee28faa 100644
--- a/net/tipc/node.c
+++ b/net/tipc/node.c
@@ -1831,12 +1831,13 @@ static void tipc_node_mcast_rcv(struct tipc_node *n)
 }
 
 static void tipc_node_bc_sync_rcv(struct tipc_node *n, struct tipc_msg *hdr,
-				  int bearer_id, struct sk_buff_head *xmitq)
+				  int bearer_id, struct sk_buff_head *xmitq,
+				  bool *valid)
 {
 	struct tipc_link *ucl;
 	int rc;
 
-	rc = tipc_bcast_sync_rcv(n->net, n->bc_entry.link, hdr, xmitq);
+	rc = tipc_bcast_sync_rcv(n->net, n->bc_entry.link, hdr, xmitq, valid);
 
 	if (rc & TIPC_LINK_DOWN_EVT) {
 		tipc_node_reset_links(n);
@@ -2140,12 +2141,18 @@ void tipc_rcv(struct net *net, struct sk_buff *skb, struct tipc_bearer *b)
 
 	/* Ensure broadcast reception is in synch with peer's send state */
 	if (unlikely(usr == LINK_PROTOCOL)) {
+		bool valid = true;
+
 		if (unlikely(skb_linearize(skb))) {
 			tipc_node_put(n);
 			goto discard;
 		}
 		hdr = buf_msg(skb);
-		tipc_node_bc_sync_rcv(n, hdr, bearer_id, &xmitq);
+		tipc_node_bc_sync_rcv(n, hdr, bearer_id, &xmitq, &valid);
+		if (!valid) {
+			tipc_node_put(n);
+			goto discard;
+		}
 	} else if (unlikely(tipc_link_acked(n->bc_entry.link) != bc_ack)) {
 		tipc_bcast_ack_rcv(net, n->bc_entry.link, hdr);
 	}

gemini-3.1-pro-preview

null

null

							input: 3241
							output: 30
							thoughts: 223
						

**Analyzing a TIPC Patch**

Okay, so I'm looking at this patch for TIPC, and it looks like a targeted fix related to broadcast synchronization. They've updated `net/tipc/bcast.c`, `net/tipc/bcast.h`, and `net/tipc/node.c`. The key change seems to be in `tipc_bcast_sync_rcv`. They've added a `bool *valid` argument, and now they're validating the Gap ACK blocks. Specifically, it seems they're checking if the received data size (`glen`) is larger than what's expected (`msg_data_sz(hdr)`). If there's an issue with the size, `valid` gets set to `false`, and the processing is skipped. This `valid` flag is then propagated up through `tipc_node_bc_sync_rcv` and eventually checked in `tipc_rcv`, which discards the `skb` if it's invalid.

Essentially, this is a functional enhancement – adding some validation to the broadcast sync receive process in TIPC. I'm assuming this is to prevent buffer overflows or other related issues in the receive process. It's a smart addition and very likely to be a good target for fuzzing. I can definitely see how malformed Gap ACKs could be exploited if they weren't validated.

Now, let's track down the TIPC configuration. I bet `CONFIG_TIPC` is the primary one, but I should probably take a look at `net/tipc/Kconfig` to see if there are any other related configs or any other modules I should consider fuzzing.

{
  "Expression": "config TIPC",
  "PathPrefix": "net/tipc/Kconfig"
}

{
  "Output": "net/tipc/Kconfig-5-\nnet/tipc/Kconfig:6:menuconfig TIPC\nnet/tipc/Kconfig-7-\ttristate \"The TIPC Protocol\"\n--\nnet/tipc/Kconfig-23-\nnet/tipc/Kconfig:24:config TIPC_MEDIA_IB\nnet/tipc/Kconfig-25-\tbool \"InfiniBand media type support\"\n--\nnet/tipc/Kconfig-29-\t  IP-over-InfiniBand devices.\nnet/tipc/Kconfig:30:config TIPC_MEDIA_UDP\nnet/tipc/Kconfig-31-\tbool \"IP/UDP media type support\"\n--\nnet/tipc/Kconfig-37-\nnet/tipc/Kconfig:38:config TIPC_CRYPTO\nnet/tipc/Kconfig-39-\tbool \"TIPC encryption support\"\n--\nnet/tipc/Kconfig-52-\nnet/tipc/Kconfig:53:config TIPC_DIAG\nnet/tipc/Kconfig-54-\ttristate \"TIPC: socket monitoring interface\"\n"
}

gemini-3.1-pro-preview

null

null

							input: 4144
							output: 35
							thoughts: 186
						

**Focusing on TIPC Vulnerabilities**

Okay, so I'm looking at TIPC, specifically its configuration. The primary configuration item is `TIPC`, obviously. I see we can also enable `TIPC_MEDIA_UDP` which is interesting because that means we can open it up for fuzzing over UDP. Let's dig in and figure out where the best places to focus our efforts are.

I need to identify the key functions. Immediately, `tipc_bcast_sync_rcv`, `tipc_node_bc_sync_rcv`, and most importantly, `tipc_rcv`, jump out at me. I'll need to confirm, but `tipc_rcv` seems like the central receive function for TIPC, so it's likely a hot-path function and the most important.

`tipc_bcast_sync_rcv` handles broadcast synchronization messages, and `tipc_node_bc_sync_rcv` looks like a static function residing in `net/tipc/node.c`. Now, my next step is clear: I need to scrutinize both `tipc_bcast_sync_rcv` and `tipc_node_bc_sync_rcv` thoroughly. I'll start with those and see where they lead.

{
  "Expression": "tipc_bcast_sync_rcv",
  "PathPrefix": "net/tipc/"
}

{
  "Output": "net/tipc/bcast.c=470=void tipc_bcast_ack_rcv(struct net *net, struct tipc_link *l,\n--\nnet/tipc/bcast.c-497- */\nnet/tipc/bcast.c:498:int tipc_bcast_sync_rcv(struct net *net, struct tipc_link *l,\nnet/tipc/bcast.c-499-\t\t\tstruct tipc_msg *hdr,\n--\nnet/tipc/bcast.h=96=void tipc_bcast_ack_rcv(struct net *net, struct tipc_link *l,\nnet/tipc/bcast.h-97-\t\t\tstruct tipc_msg *hdr);\nnet/tipc/bcast.h:98:int tipc_bcast_sync_rcv(struct net *net, struct tipc_link *l,\nnet/tipc/bcast.h-99-\t\t\tstruct tipc_msg *hdr,\n--\nnet/tipc/node.c=1833=static void tipc_node_bc_sync_rcv(struct tipc_node *n, struct tipc_msg *hdr,\n--\nnet/tipc/node.c-1839-\nnet/tipc/node.c:1840:\trc = tipc_bcast_sync_rcv(n-\u003enet, n-\u003ebc_entry.link, hdr, xmitq, valid);\nnet/tipc/node.c-1841-\n"
}

gemini-3.1-pro-preview

null

null

							input: 5034
							output: 36
							thoughts: 103
						

Okay, here's my understanding, considering I'm trying to pinpoint the key areas for analysis:

**Focusing on TIPC Broadcast Synchronization**

Right, so I'm honing in on the broadcast synchronization mechanisms within the TIPC (Transparent Inter-Process Communication) system. I've identified `tipc_bcast_sync_rcv` as a strong candidate for closer inspection, and `tipc_node_bc_sync_rcv` seems equally promising. It looks like `tipc_rcv` is the central receiving function, which could be a performance bottleneck – it's likely a hot spot. However, `tipc_node_bc_sync_rcv` is invoked from within `tipc_rcv` specifically when the `usr` parameter indicates a `LINK_PROTOCOL` context, suggesting it handles node-level broadcast synchronization.

Now, a related area that springs to mind is how TIPC deals with acknowledgements and gaps in received data. I should investigate `tipc_get_gap_ack_blks` to see if it plays a significant role in the broadcast synchronization process, especially related to the handling of lost or fragmented broadcast packets. I need to understand if it’s involved in the synchronization strategy, or only concerns data reliability.

{
  "Expression": "tipc_get_gap_ack_blks",
  "PathPrefix": "net/tipc/"
}

{
  "Output": "net/tipc/bcast.c=498=int tipc_bcast_sync_rcv(struct net *net, struct tipc_link *l,\n--\nnet/tipc/bcast.c-513-\t} else if (!msg_bc_ack_invalid(hdr)) {\nnet/tipc/bcast.c:514:\t\tglen = tipc_get_gap_ack_blks(\u0026ga, l, hdr, false);\nnet/tipc/bcast.c-515-\t\tif (glen \u003e msg_data_sz(hdr)) {\n--\nnet/tipc/link.c=1340=static int tipc_link_tnl_rcv(struct tipc_link *l, struct sk_buff *skb,\n--\nnet/tipc/link.c-1405-/**\nnet/tipc/link.c:1406: * tipc_get_gap_ack_blks - get Gap ACK blocks from PROTOCOL/STATE_MSG\nnet/tipc/link.c-1407- * @ga: returned pointer to the Gap ACK blocks if any\n--\nnet/tipc/link.c-1413- */\nnet/tipc/link.c:1414:u16 tipc_get_gap_ack_blks(struct tipc_gap_ack_blks **ga, struct tipc_link *l,\nnet/tipc/link.c-1415-\t\t\t  struct tipc_msg *hdr, bool uc)\n--\nnet/tipc/link.c=2174=static int tipc_link_proto_rcv(struct tipc_link *l, struct sk_buff *skb,\n--\nnet/tipc/link.c-2271-\t\t/* Validate Gap ACK blocks, drop if invalid */\nnet/tipc/link.c:2272:\t\tglen = tipc_get_gap_ack_blks(\u0026ga, l, hdr, true);\nnet/tipc/link.c-2273-\t\tif (glen \u003e dlen)\n--\nnet/tipc/link.h=144=int tipc_link_mss(struct tipc_link *l);\nnet/tipc/link.h:145:u16 tipc_get_gap_ack_blks(struct tipc_gap_ack_blks **ga, struct tipc_link *l,\nnet/tipc/link.h-146-\t\t\t  struct tipc_msg *hdr, bool uc);\n"
}

gemini-3.1-pro-preview

null

null

							input: 6070
							output: 121
							thoughts: 178
						

**My Analysis of the TIPC Patch**

Okay, so this patch is introducing a new validation check, specifically `glen > msg_data_sz(hdr)`, and it's being inserted after a call to `tipc_get_gap_ack_blks`. That's interesting, and immediately points me to the core logic of `tipc_bcast_sync_rcv` and `tipc_node_bc_sync_rcv`. Those are definitely the functions I need to scrutinize. They are the clear focus symbols here. I'm thinking they are the best points to begin the analysis.

Now, let me put together a concise summary of my findings. This is clearly a situation where fuzzing is warranted – **WorthFuzzing: true**. My analysis indicates the best fuzzing target symbols are `tipc_bcast_sync_rcv` and `tipc_node_bc_sync_rcv` – **FocusSymbols: tipc_bcast_sync_rcv, tipc_node_bc_sync_rcv**. I'd also expect the relevant kernel configurations will include `TIPC` and likely `TIPC_MEDIA_UDP` - **EnableConfigs: TIPC, TIPC_MEDIA_UDP**.

My reasoning is straightforward: this patch is fundamentally about improving the robustness of the TIPC broadcast sync receive. The new validation is directly aimed at preventing out-of-bounds access or the processing of maliciously crafted or malformed messages, specifically related to Gap ACK blocks. This is a functional change, a direct modification to how the network protocol is handled. Therefore, fuzzing the logic impacted by this check, especially the two functions identified, is absolutely critical for security and stability.

{
  "EnableConfigs": [
    "TIPC",
    "TIPC_MEDIA_UDP"
  ],
  "FocusSymbols": [
    "tipc_bcast_sync_rcv",
    "tipc_node_bc_sync_rcv"
  ],
  "Reasoning": "The patch adds validation for Gap ACK blocks in TIPC broadcast sync receive to prevent processing of malformed messages. This is a functional change in the network protocol handling that should be fuzzed to ensure the validation correctly handles malformed packets without causing regressions.",
  "WorthFuzzing": true
}

{
  "EnableConfigs": [
    "TIPC",
    "TIPC_MEDIA_UDP"
  ],
  "FocusSymbols": [
    "tipc_bcast_sync_rcv",
    "tipc_node_bc_sync_rcv"
  ],
  "Reasoning": "The patch adds validation for Gap ACK blocks in TIPC broadcast sync receive to prevent processing of malformed messages. This is a functional change in the network protocol handling that should be fuzzed to ensure the validation correctly handles malformed packets without causing regressions.",
  "WorthFuzzing": true
}