CVE-2024-40959 (Moderate severity, published 2024-07-11)
CVSS score: 5.5 (CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H)
CWE: CWE-476
Description: In the Linux kernel, the following vulnerability has been resolved:

xfrm6: check ip6_dst_idev() return value in xfrm6_get_saddr()

ip6_dst_idev() can return NULL, xfrm6_get_saddr() must act accordingly.

syzbot reported:

Oops: general protection fault, probably for non-canonical address 0xdffffc0000000000: 0000 [#1] PREEMPT SMP KASAN PTI
KASAN: null-ptr-deref in range [0x0000000000000000-0x0000000000000007]
CPU: 1 PID: 12 Comm: kworker/u8:1 Not tainted 6.10.0-rc2-syzkaller-00383-gb8481381d4e2 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/02/2024
Workqueue: wg-kex-wg1 wg_packet_handshake_send_worker
 RIP: 0010:xfrm6_get_saddr+0x93/0x130 net/ipv6/xfrm6_policy.c:64
Code: df 48 89 fa 48 c1 ea 03 80 3c 02 00 0f 85 97 00 00 00 4c 8b ab d8 00 00 00 48 b8 00 00 00 00 00 fc ff df 4c 89 ea 48 c1 ea 03 <80> 3c 02 00 0f 85 86 00 00 00 4d 8b 6d 00 e8 ca 13 47 01 48 b8 00
RSP: 0018:ffffc90000117378 EFLAGS: 00010246
RAX: dffffc0000000000 RBX: ffff88807b079dc0 RCX: ffffffff89a0d6d7
RDX: 0000000000000000 RSI: ffffffff89a0d6e9 RDI: ffff88807b079e98
RBP: ffff88807ad73248 R08: 0000000000000007 R09: fffffffffffff000
R10: ffff88807b079dc0 R11: 0000000000000007 R12: ffffc90000117480
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
FS:  0000000000000000(0000) GS:ffff8880b9300000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f4586d00440 CR3: 0000000079042000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
  xfrm_get_saddr net/xfrm/xfrm_policy.c:2452 [inline]
  xfrm_tmpl_resolve_one net/xfrm/xfrm_policy.c:2481 [inline]
  xfrm_tmpl_resolve+0xa26/0xf10 net/xfrm/xfrm_policy.c:2541
  xfrm_resolve_and_create_bundle+0x140/0x2570 net/xfrm/xfrm_policy.c:2835
  xfrm_bundle_lookup net/xfrm/xfrm_policy.c:3070 [inline]
  xfrm_lookup_with_ifid+0x4d1/0x1e60 net/xfrm/xfrm_policy.c:3201
  xfrm_lookup net/xfrm/xfrm_policy.c:3298 [inline]
  xfrm_lookup_route+0x3b/0x200 net/xfrm/xfrm_policy.c:3309
  ip6_dst_lookup_flow+0x15c/0x1d0 net/ipv6/ip6_output.c:1256
  send6+0x611/0xd20 drivers/net/wireguard/socket.c:139
  wg_socket_send_skb_to_peer+0xf9/0x220 drivers/net/wireguard/socket.c:178
  wg_socket_send_buffer_to_peer+0x12b/0x190 drivers/net/wireguard/socket.c:200
  wg_packet_send_handshake_initiation+0x227/0x360 drivers/net/wireguard/send.c:40
  wg_packet_handshake_send_worker+0x1c/0x30 drivers/net/wireguard/send.c:51
  process_one_work+0x9fb/0x1b60 kernel/workqueue.c:3231
  process_scheduled_works kernel/workqueue.c:3312 [inline]
  worker_thread+0x6c8/0xf70 kernel/workqueue.c:3393
  kthread+0x2c1/0x3a0 kernel/kthread.c:389
  ret_from_fork+0x45/0x80 arch/x86/kernel/process.c:147
  ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
Mitigation: Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base or stability.