[PATCH 6.6 176/396] wireguard: netlink: check for dangling peer via is_dead instead of empty list

Greg Kroah-Hartman
2024-04-01T16:44:26Z

From: Jason A. Donenfeld <Jason@zx2c4.com>

[ Upstream commit 55b6c738673871c9b0edae05d0c97995c1ff08c4 ]

If all peers are removed via wg_peer_remove_all(), rather than setting
peer_list to empty, the peer is added to a temporary list with a head on
the stack of wg_peer_remove_all(). If a netlink dump is resumed and the
cursored peer is one that has been removed via wg_peer_remove_all(), it
will iterate from that peer and then attempt to dump freed peers.

Fix this by instead checking peer->is_dead, which was explictly created
for this purpose. Also move up the device_update_lock lockdep assertion,
since reading is_dead relies on that.

It can be reproduced by a small script like:

echo "Setting config..."
ip link add dev wg0 type wireguard
wg setconf wg0 /big-config
(
while true; do
echo "Showing config..."
wg showconf wg0 > /dev/null
done
) &
sleep 4
wg setconf wg0 <(printf "[Peer]\nPublicKey=$(wg genkey)\n")

Resulting in:

BUG: KASAN: slab-use-after-free in __lock_acquire+0x182a/0x1b20
Read of size 8 at addr ffff88811956ec70 by task wg/59
CPU: 2 PID: 59 Comm: wg Not tainted 6.8.0-rc2-debug+ #5
Call Trace:
<TASK>
dump_stack_lvl+0x47/0x70
print_address_description.constprop.0+0x2c/0x380
print_report+0xab/0x250
kasan_report+0xba/0xf0
__lock_acquire+0x182a/0x1b20
lock_acquire+0x191/0x4b0
down_read+0x80/0x440
get_peer+0x140/0xcb0
wg_get_device_dump+0x471/0x1130

Cc: stable@vger.kernel.org
Fixes: e7096c131e51 ("net: WireGuard secure network tunnel")
Reported-by: Lillian Berry <lillian@star-ark.net>
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
Reviewed-by: Jiri Pirko <jiri@nvidia.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/net/wireguard/netlink.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/net/wireguard/netlink.c b/drivers/net/wireguard/netlink.c
index dc09b75a32485..12d80306ff3bc 100644
--- a/drivers/net/wireguard/netlink.c
+++ b/drivers/net/wireguard/netlink.c
@@ -255,17 +255,17 @@ static int wg_get_device_dump(struct sk_buff *skb, struct netlink_callback *cb)
if (!peers_nest)
goto out;
ret = 0;
- /* If the last cursor was removed via list_del_init in peer_remove, then
+ lockdep_assert_held(&wg->device_update_lock);
+ /* If the last cursor was removed in peer_remove or peer_remove_all, then
* we just treat this the same as there being no more peers left. The
* reason is that seq_nr should indicate to userspace that this isn't a
* coherent dump anyway, so they'll try again.
*/
if (list_empty(&wg->peer_list) ||
- (ctx->next_peer && list_empty(&ctx->next_peer->peer_list))) {
+ (ctx->next_peer && ctx->next_peer->is_dead)) {
nla_nest_cancel(skb, peers_nest);
goto out;
}
- lockdep_assert_held(&wg->device_update_lock);
peer = list_prepare_entry(ctx->next_peer, &wg->peer_list, peer_list);
list_for_each_entry_continue(peer, &wg->peer_list, peer_list) {
if (get_peer(peer, skb, ctx)) {
--
2.43.0