This is a note to let you know that I've just added the patch titled
af_unix: Annotate data-race of sk->sk_state in unix_inq_len().
to the 5.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
af_unix-annotate-data-race-of-sk-sk_state-in-unix_in.patch
and it can be found in the queue-5.4 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 97d20d950dde3a2bac290ece7f04282a7c0d394b
Author: Kuniyuki Iwashima <kuniyu@xxxxxxxxxx>
Date: Tue Jun 4 09:52:29 2024 -0700
af_unix: Annotate data-race of sk->sk_state in unix_inq_len().
[ Upstream commit 3a0f38eb285c8c2eead4b3230c7ac2983707599d ]
ioctl(SIOCINQ) calls unix_inq_len() that checks sk->sk_state first
and returns -EINVAL if it's TCP_LISTEN.
Then, for SOCK_STREAM sockets, unix_inq_len() returns the number of
bytes in recvq.
However, unix_inq_len() does not hold unix_state_lock(), and the
concurrent listen() might change the state after checking sk->sk_state.
If the race occurs, 0 is returned for the listener, instead of -EINVAL,
because the length of skb with embryo is 0.
We could hold unix_state_lock() in unix_inq_len(), but it's overkill
given the result is true for pre-listen() TCP_CLOSE state.
So, let's use READ_ONCE() for sk->sk_state in unix_inq_len().
Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Signed-off-by: Kuniyuki Iwashima <kuniyu@xxxxxxxxxx>
Signed-off-by: Paolo Abeni <pabeni@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c
index e8bad973285e4..8ab1e2a781195 100644
--- a/net/unix/af_unix.c
+++ b/net/unix/af_unix.c
@@ -2579,7 +2579,7 @@ long unix_inq_len(struct sock *sk)
struct sk_buff *skb;
long amount = 0;
- if (sk->sk_state == TCP_LISTEN)
+ if (READ_ONCE(sk->sk_state) == TCP_LISTEN)
return -EINVAL;
spin_lock(&sk->sk_receive_queue.lock);
