Commit ccf7abb9 authored Feb 03, 2017 by Eric Dumazet Committed by David S. Miller Feb 06, 2017

tcp: avoid infinite loop in tcp_splice_read()



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: Eric Dumazet <edumazet@google.com>
Reported-by: Dmitry Vyukov <dvyukov@google.com>
Cc: Willy Tarreau <w@1wt.eu>
Signed-off-by: David S. Miller <davem@davemloft.net>

parent b3f2d07f

net/ipv4/tcp.c

+6 −0

Original line number	Diff line number	Diff line
		@@ -770,6 +770,12 @@ 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, NULL);
		if (signal_pending(current)) {
		ret = sock_intr_errno(timeo);

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