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af_unix: Don't set -ECONNRESET for consumed OOB skb.

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[ Upstream commit 2a5a484184 ]

Christian Brauner reported that even after MSG_OOB data is consumed,
calling close() on the receiver socket causes the peer's recv() to
return -ECONNRESET:

  1. send() and recv() an OOB data.

    >>> from socket import *
    >>> s1, s2 = socketpair(AF_UNIX, SOCK_STREAM)
    >>> s1.send(b'x', MSG_OOB)
    1
    >>> s2.recv(1, MSG_OOB)
    b'x'

  2. close() for s2 sets ECONNRESET to s1->sk_err even though
     s2 consumed the OOB data

    >>> s2.close()
    >>> s1.recv(10, MSG_DONTWAIT)
    ...
    ConnectionResetError: [Errno 104] Connection reset by peer

Even after being consumed, the skb holding the OOB 1-byte data stays in
the recv queue to mark the OOB boundary and break recv() at that point.

This must be considered while close()ing a socket.

Let's skip the leading consumed OOB skb while checking the -ECONNRESET
condition in unix_release_sock().

Fixes: 314001f0bf ("af_unix: Add OOB support")
Reported-by: Christian Brauner <brauner@kernel.org>
Closes: https://lore.kernel.org/netdev/20250529-sinkt-abfeuern-e7b08200c6b0@brauner/
Signed-off-by: Kuniyuki Iwashima <kuniyu@google.com>
Acked-by: Christian Brauner <brauner@kernel.org>
Link: https://patch.msgid.link/20250619041457.1132791-4-kuni1840@gmail.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Kuniyuki Iwashima 2025-06-18 21:13:57 -07:00 committed by Greg Kroah-Hartman
parent 4c3e0c11ba
commit d9ac9826f5
1 changed files with 12 additions and 6 deletions
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18
net/unix/af_unix.c
View File

@ -577,6 +577,11 @@ static void unix_sock_destructor(struct sock *sk)
#endif
}
static unsigned int unix_skb_len(const struct sk_buff *skb)
{
return skb->len - UNIXCB(skb).consumed;
}
static void unix_release_sock(struct sock *sk, int embrion)
{
struct unix_sock *u = unix_sk(sk);
@ -611,10 +616,16 @@ static void unix_release_sock(struct sock *sk, int embrion)
if (skpair != NULL) {
if (sk->sk_type == SOCK_STREAM || sk->sk_type == SOCK_SEQPACKET) {
struct sk_buff *skb = skb_peek(&sk->sk_receive_queue);
#if IS_ENABLED(CONFIG_AF_UNIX_OOB)
if (skb && !unix_skb_len(skb))
skb = skb_peek_next(skb, &sk->sk_receive_queue);
#endif
unix_state_lock(skpair);
/* No more writes */
WRITE_ONCE(skpair->sk_shutdown, SHUTDOWN_MASK);
if (!skb_queue_empty_lockless(&sk->sk_receive_queue) || embrion)
if (skb || embrion)
WRITE_ONCE(skpair->sk_err, ECONNRESET);
unix_state_unlock(skpair);
skpair->sk_state_change(skpair);
@ -2593,11 +2604,6 @@ static long unix_stream_data_wait(struct sock *sk, long timeo,
return timeo;
}
static unsigned int unix_skb_len(const struct sk_buff *skb)
{
return skb->len - UNIXCB(skb).consumed;
}
struct unix_stream_read_state {
int (*recv_actor)(struct sk_buff *, int, int,
struct unix_stream_read_state *);