From cd3b9e464ca54547965df76463bdfb26e6712287 Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Fri, 3 Feb 2017 14:59:38 -0800 Subject: [PATCH] tcp: avoid infinite loop in tcp_splice_read() commit ccf7abb93af09ad0868ae9033d1ca8108bdaec82 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: 9c55e01c0cc8 ("[TCP]: Splice receive support.") Signed-off-by: Eric Dumazet Reported-by: Dmitry Vyukov Cc: Willy Tarreau Signed-off-by: David S. Miller [bwh: Backported to 3.2: adjust context] Signed-off-by: Ben Hutchings --- net/ipv4/tcp.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c index 9a7c01e5cb8d..80a9a9710726 100644 --- a/net/ipv4/tcp.c +++ b/net/ipv4/tcp.c @@ -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); -- 2.39.2