From 0f895f51a831d73ce24158534784aba5b2a72a9e 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() [ 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. CVE: CVE-2017-6214 Upstream-Status: Backport [from kernel.org longterm 4.9.52] Fixes: 9c55e01c0cc8 ("[TCP]: Splice receive support.") Signed-off-by: Eric Dumazet Reported-by: Dmitry Vyukov Cc: Willy Tarreau Signed-off-by: David S. Miller Signed-off-by: Greg Kroah-Hartman Signed-off-by: Sona Sarmadi --- net/ipv4/tcp.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c index 814af89..6a90a0e 100644 --- a/net/ipv4/tcp.c +++ b/net/ipv4/tcp.c @@ -772,6 +772,12 @@ 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); -- 1.9.1