Path: csiph.com!goblin2!goblin.stu.neva.ru!news.unit0.net!news.panservice.it!bofh.it!news.nic.it!robomod From: Willy Tarreau Newsgroups: linux.kernel Subject: [PATCH 3.10 011/250] tcp: avoid infinite loop in tcp_splice_read() Date: Thu, 08 Jun 2017 01:10:03 +0200 Message-ID: References: X-Mailer: git-send-email 2.8.0.rc2.1.gbe9624a Sender: robomod@news.nic.it List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Approved: robomod@news.nic.it Lines: 44 Organization: linux.* mail to news gateway X-Original-Cc: Eric Dumazet , Willy Tarreau , "David S . Miller" X-Original-Date: Thu, 8 Jun 2017 00:56:37 +0200 X-Original-Message-ID: <1496876436-32402-12-git-send-email-w@1wt.eu> X-Original-References: <1496876436-32402-1-git-send-email-w@1wt.eu> X-Original-Sender: linux-kernel-owner@vger.kernel.org Xref: csiph.com linux.kernel:1660322 From: Eric Dumazet 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 Signed-off-by: Willy Tarreau --- net/ipv4/tcp.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c index 5d4bd6c..d1e0422 100644 --- a/net/ipv4/tcp.c +++ b/net/ipv4/tcp.c @@ -723,6 +723,12 @@ 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); -- 2.8.0.rc2.1.gbe9624a