CVE-2024-26951

In the Linux kernel, the following vulnerability has been resolved:

wireguard: netlink: check for dangling peer via is_dead instead of empty list

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

Affected Software

References

• https://git.kernel.org/stable/c/13d107794304306164481d31ce33f8fdb25a9c04
• https://git.kernel.org/stable/c/302b2dfc013baca3dea7ceda383930d9297d231d
• https://git.kernel.org/stable/c/55b6c738673871c9b0edae05d0c97995c1ff08c4
• https://git.kernel.org/stable/c/710a177f347282eea162aec8712beb1f42d5ad87
• https://git.kernel.org/stable/c/7bedfe4cfa38771840a355970e4437cd52d4046b
• https://git.kernel.org/stable/c/b7cea3a9af0853fdbb1b16633a458f991dde6aac
• https://git.kernel.org/stable/c/f52be46e3e6ecefc2539119784324f0cbc09620a
• https://lists.debian.org/debian-lts-announce/2024/06/msg00017.html