From: Eric Dumazet <edumazet@google.com>
Date: Fri, 3 Feb 2017 22:59:38 +0000 (-0800)
Subject: tcp: avoid infinite loop in tcp_splice_read()
X-Git-Tag: v4.1.12-102.0.20170529_2200~27
X-Git-Url: https://www.infradead.org/git/?a=commitdiff_plain;h=e0f4d5231e2cb1d86f8f563c60d0c1349753ccd9;p=users%2Fjedix%2Flinux-maple.git

tcp: avoid infinite loop in tcp_splice_read()

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.

Orabug: 25802549
CVE: CVE-2017-6214

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 : Aniket Alshi <aniket.alsi@oracle.com>
(cherry picked from commit ccf7abb93af09ad0868ae9033d1ca8108bdaec82)
Reviewed-by: Jack Vogel <jack.vogel@oracle.com>
---

diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index 88d001a468ae2..1d0f14891b5c1 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -781,6 +781,12 @@ 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);