Commit cd3b9e46 authored by Eric Dumazet's avatar Eric Dumazet Committed by Ben Hutchings

tcp: avoid infinite loop in tcp_splice_read()

commit ccf7abb9 upstream.

Splicing from TCP socket is vulnerable when a packet with URG flag is
received and stored into receive queue.

__tcp_splice_read() returns 0, and sk_wait_data() immediately
returns since there is the problematic skb in queue.

This is a nice way to burn cpu (aka infinite loop) and trigger
soft lockups.

Again, this gem was found by syzkaller tool.

Fixes: 9c55e01c ("[TCP]: Splice receive support.")
Signed-off-by: default avatarEric Dumazet <edumazet@google.com>
Reported-by: default avatarDmitry Vyukov  <dvyukov@google.com>
Cc: Willy Tarreau <w@1wt.eu>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
[bwh: Backported to 3.2: adjust context]
Signed-off-by: default avatarBen Hutchings <ben@decadent.org.uk>
parent fd75b79e
......@@ -659,6 +659,12 @@ ssize_t tcp_splice_read(struct socket *sock, loff_t *ppos,
ret = -EAGAIN;
break;
}
/* if __tcp_splice_read() got nothing while we have
* an skb in receive queue, we do not want to loop.
* This might happen with URG data.
*/
if (!skb_queue_empty(&sk->sk_receive_queue))
break;
sk_wait_data(sk, &timeo);
if (signal_pending(current)) {
ret = sock_intr_errno(timeo);
......
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