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Message-Id: <20170216175259.944361093@linuxfoundation.org>
Date: Thu, 16 Feb 2017 09:53:40 -0800
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-kernel@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
stable@...r.kernel.org, Eric Dumazet <edumazet@...gle.com>,
Dmitry Vyukov <dvyukov@...gle.com>, Willy Tarreau <w@....eu>,
"David S. Miller" <davem@...emloft.net>
Subject: [PATCH 4.4 10/20] tcp: avoid infinite loop in tcp_splice_read()
4.4-stable review patch. If anyone has any objections, please let me know.
------------------
From: Eric Dumazet <edumazet@...gle.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@...gle.com>
Reported-by: Dmitry Vyukov <dvyukov@...gle.com>
Cc: Willy Tarreau <w@....eu>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
net/ipv4/tcp.c | 6 ++++++
1 file changed, 6 insertions(+)
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -783,6 +783,12 @@ 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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