| From | Jiri Slaby <> | Subject | [PATCH 3.12 057/113] tcp: avoid infinite loop in tcp_splice_read() | Date | Mon, 6 Mar 2017 10:11:21 +0100 |
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From: Eric Dumazet <edumazet@google.com>
3.12-stable review patch. If anyone has any objections, please let me know.
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[ Upstream commit ccf7abb93af09ad0868ae9033d1ca8108bdaec82 ]
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: 9c55e01c0cc8 ("[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> Signed-off-by: Jiri Slaby <jslaby@suse.cz> --- net/ipv4/tcp.c | 6 ++++++ 1 file changed, 6 insertions(+)
diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c index 3e63b5fb2121..3d2e55c5458e 100644 --- a/net/ipv4/tcp.c +++ b/net/ipv4/tcp.c @@ -722,6 +722,12 @@ 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); -- 2.12.0
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