This is a note to let you know that I've just added the patch titled net/x25: Fix null-ptr-deref in x25_connect to the 5.9-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: net-x25-fix-null-ptr-deref-in-x25_connect.patch and it can be found in the queue-5.9 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. >From foo@baz Mon Nov 16 07:48:29 PM CET 2020 From: Martin Schiller <ms@xxxxxxxxxx> Date: Mon, 9 Nov 2020 07:54:49 +0100 Subject: net/x25: Fix null-ptr-deref in x25_connect From: Martin Schiller <ms@xxxxxxxxxx> [ 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@xxxxxxxxxx> Reviewed-by: Xie He <xie.he.0141@xxxxxxxxx> Link: https://lore.kernel.org/r/20201109065449.9014-1-ms@xxxxxxxxxx Signed-off-by: Jakub Kicinski <kuba@xxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- 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 @@ -825,7 +825,7 @@ 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; Patches currently in stable-queue which might be from ms@xxxxxxxxxx are queue-5.9/net-x25-fix-null-ptr-deref-in-x25_connect.patch