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authorEric Dumazet <edumazet@google.com>2017-02-03 14:59:38 -0800
committerBen Hutchings <ben@decadent.org.uk>2017-02-26 20:01:32 +0000
commitcd3b9e464ca54547965df76463bdfb26e6712287 (patch)
parentfd75b79ea9c7cf89d5b95f9896c6b4dcdac8c4cb (diff)
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 <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> [bwh: Backported to 3.2: adjust context] Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
1 files changed, 6 insertions, 0 deletions
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;
+ /* 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);