Subject: CVE-2024-26951: wireguard: netlink: check for dangling peer via is_dead instead of empty list

From: Greg Kroah-Hartman <[email-masked]>

Description
===========

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

The Linux kernel CVE team has assigned CVE-2024-26951 to this issue.

Affected and fixed versions
===========================

	Issue introduced in 5.6 with commit e7096c131e51 and fixed in 5.10.215 with commit f52be46e3e6e
	Issue introduced in 5.6 with commit e7096c131e51 and fixed in 5.15.154 with commit 710a177f3472
	Issue introduced in 5.6 with commit e7096c131e51 and fixed in 6.1.84 with commit b7cea3a9af08
	Issue introduced in 5.6 with commit e7096c131e51 and fixed in 6.6.24 with commit 13d107794304
	Issue introduced in 5.6 with commit e7096c131e51 and fixed in 6.7.12 with commit 7bedfe4cfa38
	Issue introduced in 5.6 with commit e7096c131e51 and fixed in 6.8.3 with commit 302b2dfc013b
	Issue introduced in 5.6 with commit e7096c131e51 and fixed in 6.9 with commit 55b6c7386738

Please see https://www.kernel.org for a full list of currently supported
kernel versions by the kernel community.

Unaffected versions might change over time as fixes are backported to
older supported kernel versions.  The official CVE entry at
	https://cve.org/CVERecord/?id=CVE-2024-26951
will be updated if fixes are backported, please check that for the most
up to date information about this issue.

Affected files
==============

The file(s) affected by this issue are:
	drivers/net/wireguard/netlink.c

Mitigation
==========

The Linux kernel CVE team recommends that you update to the latest
stable kernel version for this, and many other bugfixes.  Individual
changes are never tested alone, but rather are part of a larger kernel
release.  Cherry-picking individual commits is not recommended or
supported by the Linux kernel community at all.  If however, updating to
the latest release is impossible, the individual changes to resolve this
issue can be found at these commits:
	https://git.kernel.org/stable/c/f52be46e3e6ecefc2539119784324f0cbc09620a
	https://git.kernel.org/stable/c/710a177f347282eea162aec8712beb1f42d5ad87
	https://git.kernel.org/stable/c/b7cea3a9af0853fdbb1b16633a458f991dde6aac
	https://git.kernel.org/stable/c/13d107794304306164481d31ce33f8fdb25a9c04
	https://git.kernel.org/stable/c/7bedfe4cfa38771840a355970e4437cd52d4046b
	https://git.kernel.org/stable/c/302b2dfc013baca3dea7ceda383930d9297d231d
	https://git.kernel.org/stable/c/55b6c738673871c9b0edae05d0c97995c1ff08c4