Messages in this thread Patch in this message | | | From | Greg Kroah-Hartman <> | Subject | [PATCH 4.9 13/32] tcp: avoid infinite loop in tcp_splice_read() | Date | Thu, 16 Feb 2017 09:54:49 -0800 |
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4.9-stable review patch. If anyone has any objections, please let me know.
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From: Eric Dumazet <edumazet@google.com>
[ 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: Greg Kroah-Hartman <gregkh@linuxfoundation.org> --- net/ipv4/tcp.c | 6 ++++++ 1 file changed, 6 insertions(+)
--- a/net/ipv4/tcp.c +++ b/net/ipv4/tcp.c @@ -772,6 +772,12 @@ ssize_t tcp_splice_read(struct socket *s 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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