[PATCH 5.4 283/389] Bluetooth: L2CAP: Fix l2cap_global_chan_by_psm regression

Greg Kroah-Hartman
2022-08-23T11:48:33Z

From: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>

commit 332f1795ca202489c665a75e62e18ff6284de077 upstream.

The patch d0be8347c623: "Bluetooth: L2CAP: Fix use-after-free caused
by l2cap_chan_put" from Jul 21, 2022, leads to the following Smatch
static checker warning:

net/bluetooth/l2cap_core.c:1977 l2cap_global_chan_by_psm()
error: we previously assumed 'c' could be null (see line 1996)

Fixes: d0be8347c623 ("Bluetooth: L2CAP: Fix use-after-free caused by l2cap_chan_put")
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
net/bluetooth/l2cap_core.c | 13 ++++++-------
1 file changed, 6 insertions(+), 7 deletions(-)

--- a/net/bluetooth/l2cap_core.c
+++ b/net/bluetooth/l2cap_core.c
@@ -1813,11 +1813,11 @@ static struct l2cap_chan *l2cap_global_c
bdaddr_t *dst,
u8 link_type)
{
- struct l2cap_chan *c, *c1 = NULL;
+ struct l2cap_chan *c, *tmp, *c1 = NULL;

read_lock(&chan_list_lock);

- list_for_each_entry(c, &chan_list, global_l) {
+ list_for_each_entry_safe(c, tmp, &chan_list, global_l) {
if (state && c->state != state)
continue;

@@ -1836,11 +1836,10 @@ static struct l2cap_chan *l2cap_global_c
dst_match = !bacmp(&c->dst, dst);
if (src_match && dst_match) {
c = l2cap_chan_hold_unless_zero(c);
- if (!c)
- continue;
-
- read_unlock(&chan_list_lock);
- return c;
+ if (c) {
+ read_unlock(&chan_list_lock);
+ return c;
+ }
}

/* Closest match */