[PATCH v2 net] tcp: Fix out-of-bounds access for twsk in tcp_ao_established_key().

[PATCH v2 net] tcp: Fix out-of-bounds access for twsk in tcp_ao_established_key().

[Kuniyuki Iwashima]

lockdep_sock_is_held() was added in tcp_ao_established_key()
by the cited commit.

It can be called from tcp_v[46]_timewait_ack() with twsk.

Since it does not have sk->sk_lock, the lockdep annotation
results in out-of-bound access.

  $ pahole -C tcp_timewait_sock vmlinux | grep size
  	/* size: 288, cachelines: 5, members: 8 */
  $ pahole -C sock vmlinux | grep sk_lock
  	socket_lock_t              sk_lock;              /*   440   192 */

Let's not use lockdep_sock_is_held() for TCP_TIME_WAIT.

Fixes: 6b2d11e2d8fc ("net/tcp: Add missing lockdep annotations for TCP-AO hlist traversals")
Reported-by: Damiano Melotti <melotti@google.com>
Signed-off-by: Kuniyuki Iwashima <kuniyu@google.com>
---
v2: Ensure that TCP_TIME_WAIT does not evade RCU lockdep check
v1: https://lore.kernel.org/netdev/20260506172830.2237574-1-kuniyu@google.com/
---
 net/ipv4/tcp_ao.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/net/ipv4/tcp_ao.c b/net/ipv4/tcp_ao.c
index a97cdf3e6af4..0a4b38b315fe 100644
--- a/net/ipv4/tcp_ao.c
+++ b/net/ipv4/tcp_ao.c
@@ -116,7 +116,8 @@ struct tcp_ao_key *tcp_ao_established_key(const struct sock *sk,
 {
 	struct tcp_ao_key *key;
 
-	hlist_for_each_entry_rcu(key, &ao->head, node, lockdep_sock_is_held(sk)) {
+	hlist_for_each_entry_rcu(key, &ao->head, node,
+				 sk_fullsock(sk) && lockdep_sock_is_held(sk)) {
 		if ((sndid >= 0 && key->sndid != sndid) ||
 		    (rcvid >= 0 && key->rcvid != rcvid))
 			continue;
-- 
2.54.0.563.g4f69b47b94-goog

Re: [PATCH v2 net] tcp: Fix out-of-bounds access for twsk in tcp_ao_established_key().

[Eric Dumazet]

On Fri, May 8, 2026 at 5:08 AM Kuniyuki Iwashima <kuniyu@google.com> wrote:
>
> lockdep_sock_is_held() was added in tcp_ao_established_key()
> by the cited commit.
>
> It can be called from tcp_v[46]_timewait_ack() with twsk.
>
> Since it does not have sk->sk_lock, the lockdep annotation
> results in out-of-bound access.
>
>   $ pahole -C tcp_timewait_sock vmlinux | grep size
>         /* size: 288, cachelines: 5, members: 8 */
>   $ pahole -C sock vmlinux | grep sk_lock
>         socket_lock_t              sk_lock;              /*   440   192 */
>
> Let's not use lockdep_sock_is_held() for TCP_TIME_WAIT.
>
> Fixes: 6b2d11e2d8fc ("net/tcp: Add missing lockdep annotations for TCP-AO hlist traversals")
> Reported-by: Damiano Melotti <melotti@google.com>
> Signed-off-by: Kuniyuki Iwashima <kuniyu@google.com>

Reviewed-by: Eric Dumazet <edumazet@google.com>

Re: [PATCH v2 net] tcp: Fix out-of-bounds access for twsk in tcp_ao_established_key().

[patchwork-bot+netdevbpf]

Hello:

This patch was applied to netdev/net.git (main)
by Jakub Kicinski <kuba@kernel.org>:

On Fri,  8 May 2026 12:08:46 +0000 you wrote:
> lockdep_sock_is_held() was added in tcp_ao_established_key()
> by the cited commit.
> 
> It can be called from tcp_v[46]_timewait_ack() with twsk.
> 
> Since it does not have sk->sk_lock, the lockdep annotation
> results in out-of-bound access.
> 
> [...]

Here is the summary with links:
  - [v2,net] tcp: Fix out-of-bounds access for twsk in tcp_ao_established_key().
    https://git.kernel.org/netdev/net/c/03cb001ef87b

You are awesome, thank you!
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