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af_unix: Annotate data-race of sk->sk_state in unix_inq_len().

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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: 1da177e4c3 ("Linux-2.6.12-rc2")
Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
This commit is contained in:
Kuniyuki Iwashima 2024-06-04 09:52:29 -07:00 committed by Paolo Abeni
parent 942238f973
commit 3a0f38eb28
1 changed files with 1 additions and 1 deletions
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2
net/unix/af_unix.c
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@ -3017,7 +3017,7 @@ 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);