From: Eric Dumazet
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
---
net/ipv4/tcp.c |6 ++
1 file changed, 6 insertions(+)
diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index
4a044964da6670829e5c47fef52d2cd76360b59f..0efb4c7f6704f662b6c762e48698a41564add2a4
100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -770,6 +770,12 @@ 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_receive_queue))
+ break;
sk_wait_data(sk, , NULL);
if (signal_pending(current)) {
ret = sock_intr_errno(timeo);