[ 011/135] net: sctp: fix bug in sctp_poll for SOCK_SELECT_ERR_QUEUE

[Greg Kroah-Hartman]

3.11-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Daniel Borkmann <dborkman@xxxxxxxxxx>

[ Upstream commit a0fb05d1aef0f5df936f80b726d1b3bfd4275f95 ]

If we do not add braces around ...

  mask |= POLLERR |
          sock_flag(sk, SOCK_SELECT_ERR_QUEUE) ? POLLPRI : 0;

... then this condition always evaluates to true as POLLERR is
defined as 8 and binary or'd with whatever result comes out of
sock_flag(). Hence instead of (X | Y) ? A : B, transform it into
X | (Y ? A : B). Unfortunatelty, commit 8facd5fb73 ("net: fix
smatch warnings inside datagram_poll") forgot about SCTP. :-(

Introduced by 7d4c04fc170 ("net: add option to enable error queue
packets waking select").

Signed-off-by: Daniel Borkmann <dborkman@xxxxxxxxxx>
Cc: Jacob Keller <jacob.e.keller@xxxxxxxxx>
Acked-by: Neil Horman <nhorman@xxxxxxxxxxxxx>
Acked-by: Vlad Yasevich <vyasevich@xxxxxxxxx>
Acked-by: Jacob Keller <jacob.e.keller@xxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 net/sctp/socket.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/net/sctp/socket.c
+++ b/net/sctp/socket.c
@@ -6182,7 +6182,7 @@ unsigned int sctp_poll(struct file *file
 	/* Is there any exceptional events?  */
 	if (sk->sk_err || !skb_queue_empty(&sk->sk_error_queue))
 		mask |= POLLERR |
-			sock_flag(sk, SOCK_SELECT_ERR_QUEUE) ? POLLPRI : 0;
+			(sock_flag(sk, SOCK_SELECT_ERR_QUEUE) ? POLLPRI : 0);
 	if (sk->sk_shutdown & RCV_SHUTDOWN)
 		mask |= POLLRDHUP | POLLIN | POLLRDNORM;
 	if (sk->sk_shutdown == SHUTDOWN_MASK)


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