[PATCH 4.4 44/64] net/x25: Fix null-ptr-deref in x25_connect

Greg Kroah-Hartman
2020-11-17T13:08:12Z

From: Martin Schiller <ms@dev.tdt.de>

[ Upstream commit 361182308766a265b6c521879b34302617a8c209 ]

This fixes a regression for blocking connects introduced by commit
4becb7ee5b3d ("net/x25: Fix x25_neigh refcnt leak when x25 disconnect").

The x25->neighbour is already set to "NULL" by x25_disconnect() now,
while a blocking connect is waiting in
x25_wait_for_connection_establishment(). Therefore x25->neighbour must
not be accessed here again and x25->state is also already set to
X25_STATE_0 by x25_disconnect().

Fixes: 4becb7ee5b3d ("net/x25: Fix x25_neigh refcnt leak when x25 disconnect")
Signed-off-by: Martin Schiller <ms@dev.tdt.de>
Reviewed-by: Xie He <xie.he.0141@gmail.com>
Link: https://lore.kernel.org/r/20201109065449.9014-1-ms@dev.tdt.de
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
net/x25/af_x25.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

--- a/net/x25/af_x25.c
+++ b/net/x25/af_x25.c
@@ -823,7 +823,7 @@ static int x25_connect(struct socket *so
sock->state = SS_CONNECTED;
rc = 0;
out_put_neigh:
- if (rc) {
+ if (rc && x25->neighbour) {
read_lock_bh(&x25_list_lock);
x25_neigh_put(x25->neighbour);
x25->neighbour = NULL;