possible deadlock in rtnl_lock

Status: upstream: reported on 2026/10/03 13:48
Reported-by: syzbot+80568c15ab7441229014@syzkaller.appspotmail.com
First crash: 2d19h, last: 2d15h
▶ ▼ Similar bugs (12)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
android-44 possible deadlock in rtnl_lock 4 syz, C 4676 2541d 2734d 0/2 public: reported C repro on 2019/04/12 00:00
upstream possible deadlock in rtnl_lock (5) net 4 syz, C 1009 3086d 3114d 5/29 fixed on 2018/05/08 18:30
upstream possible deadlock in rtnl_lock (3) net 4 syz, C 3633 3162d 3163d 4/29 fixed on 2018/02/07 13:48
linux-4.19 possible deadlock in rtnl_lock 4 syz, C error 31 2215d 2465d 0/1 upstream: reported C repro on 2020/01/06 01:18
upstream possible deadlock in rtnl_lock (4) net 4 syz, C 73333 3145d 3162d 4/29 fixed on 2018/02/26 20:04
upstream possible deadlock in rtnl_lock (6) net 4 syz, C done error 551 2404d 2646d 0/29 auto-obsoleted due to no activity on 2022/12/21 11:47
android-49 possible deadlock in rtnl_lock 4 syz, C 2906 2964d 3115d 0/3 closed as invalid on 2019/04/05 05:43
upstream possible deadlock in rtnl_lock net 4 syz, C 15711 3169d 3225d 4/29 fixed on 2018/02/01 04:00
linux-5.15 possible deadlock in rtnl_lock 4 42 433d 577d 0/3 auto-obsoleted due to no activity on 2025/10/07 16:45
upstream possible deadlock in rtnl_lock (2) net 4 syz, C 10369 3165d 3168d 4/29 fixed on 2018/02/04 23:45
linux-4.14 possible deadlock in rtnl_lock 4 syz, C inconclusive 312 2323d 2465d 0/1 upstream: reported C repro on 2020/01/06 01:45
upstream possible deadlock in rtnl_lock (8) net 4 syz, C 434 525d 778d 0/29 auto-obsoleted due to no activity on 2025/07/22 10:34

Sample crash report:
======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Not tainted
------------------------------------------------------
syz.1.1026/8321 is trying to acquire lock:
ffff800017a509c8 (rtnl_mutex){+.+.}-{3:3}, at: rtnl_lock+0x20/0x2c net/core/rtnetlink.c:74

but task is already holding lock:
ffff0000d0f90d40 (&wdev->mtx){+.+.}-{3:3}, at: wdev_lock net/wireless/core.h:231 [inline]
ffff0000d0f90d40 (&wdev->mtx){+.+.}-{3:3}, at: cfg80211_wext_siwgenie+0xc8/0x370 net/wireless/wext-sme.c:340

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #1 (&wdev->mtx){+.+.}-{3:3}:
       __mutex_lock_common+0x1a0/0x1f3c kernel/locking/mutex.c:603
       __mutex_lock kernel/locking/mutex.c:747 [inline]
       mutex_lock_nested+0x38/0x44 kernel/locking/mutex.c:799
       wdev_lock net/wireless/core.h:231 [inline]
       nl80211_send_iface+0x6f4/0x1128 net/wireless/nl80211.c:3885
       nl80211_notify_iface+0x5c/0x160 net/wireless/nl80211.c:17522
       cfg80211_switch_netns+0x1e8/0x4e0 net/wireless/core.c:196
       nl80211_wiphy_netns+0x128/0x228 net/wireless/nl80211.c:12128
       genl_family_rcv_msg_doit+0x210/0x308 net/netlink/genetlink.c:756
       genl_family_rcv_msg net/netlink/genetlink.c:833 [inline]
       genl_rcv_msg+0x424/0x600 net/netlink/genetlink.c:850
       netlink_rcv_skb+0x220/0x3ec net/netlink/af_netlink.c:2516
       genl_rcv+0x38/0x50 net/netlink/genetlink.c:861
       netlink_unicast_kernel net/netlink/af_netlink.c:1318 [inline]
       netlink_unicast+0x5fc/0x80c net/netlink/af_netlink.c:1344
       netlink_sendmsg+0x6f0/0x9d8 net/netlink/af_netlink.c:1877
       sock_sendmsg_nosec net/socket.c:718 [inline]
       __sock_sendmsg net/socket.c:730 [inline]
       ____sys_sendmsg+0x588/0x90c net/socket.c:2519
       ___sys_sendmsg net/socket.c:2573 [inline]
       __sys_sendmsg+0x288/0x374 net/socket.c:2602
       __do_sys_sendmsg net/socket.c:2611 [inline]
       __se_sys_sendmsg net/socket.c:2609 [inline]
       __arm64_sys_sendmsg+0x80/0x94 net/socket.c:2609
       __invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
       invoke_syscall+0x98/0x290 arch/arm64/kernel/syscall.c:52
       el0_svc_common+0x13c/0x258 arch/arm64/kernel/syscall.c:140
       do_el0_svc+0x5c/0x134 arch/arm64/kernel/syscall.c:204
       el0_svc+0x58/0x12c arch/arm64/kernel/entry-common.c:637
       el0t_64_sync_handler+0x84/0xf0 arch/arm64/kernel/entry-common.c:655
       el0t_64_sync+0x18c/0x190 arch/arm64/kernel/entry.S:585

-> #0 (rtnl_mutex){+.+.}-{3:3}:
       check_prev_add kernel/locking/lockdep.c:3162 [inline]
       check_prevs_add kernel/locking/lockdep.c:3281 [inline]
       validate_chain kernel/locking/lockdep.c:3897 [inline]
       __lock_acquire+0x3504/0x7280 kernel/locking/lockdep.c:5171
       lock_acquire+0x210/0x63c kernel/locking/lockdep.c:5790
       __mutex_lock_common+0x1a0/0x1f3c kernel/locking/mutex.c:603
       __mutex_lock kernel/locking/mutex.c:747 [inline]
       mutex_lock_nested+0x38/0x44 kernel/locking/mutex.c:799
       rtnl_lock+0x20/0x2c net/core/rtnetlink.c:74
       wext_ioctl_dispatch+0xbc/0x3d0 net/wireless/wext-core.c:996
       wext_handle_ioctl+0x1ac/0x370 net/wireless/wext-core.c:1058
       sock_ioctl+0x138/0x828 net/socket.c:1253
       vfs_ioctl fs/ioctl.c:51 [inline]
       __do_sys_ioctl fs/ioctl.c:870 [inline]
       __se_sys_ioctl fs/ioctl.c:856 [inline]
       __arm64_sys_ioctl+0x14c/0x1c8 fs/ioctl.c:856
       __invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
       invoke_syscall+0x98/0x290 arch/arm64/kernel/syscall.c:52
       el0_svc_common+0x13c/0x258 arch/arm64/kernel/syscall.c:140
       do_el0_svc+0x5c/0x134 arch/arm64/kernel/syscall.c:204
       el0_svc+0x58/0x12c arch/arm64/kernel/entry-common.c:637
       el0t_64_sync_handler+0x84/0xf0 arch/arm64/kernel/entry-common.c:655
       el0t_64_sync+0x18c/0x190 arch/arm64/kernel/entry.S:585

other info that might help us debug this:

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(&wdev->mtx);
                               lock(rtnl_mutex);
                               lock(&wdev->mtx);
  lock(rtnl_mutex);

 *** DEADLOCK ***

1 lock held by syz.1.1026/8321:
 #0: ffff0000d0f90d40 (&wdev->mtx){+.+.}-{3:3}, at: wdev_lock net/wireless/core.h:231 [inline]
 #0: ffff0000d0f90d40 (&wdev->mtx){+.+.}-{3:3}, at: cfg80211_wext_siwgenie+0xc8/0x370 net/wireless/wext-sme.c:340

stack backtrace:
CPU: 0 PID: 8321 Comm: syz.1.1026 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/14/2026
Call trace:
 dump_backtrace+0x1c4/0x1f0 arch/arm64/kernel/stacktrace.c:158
 show_stack+0x2c/0x3c arch/arm64/kernel/stacktrace.c:165
 __dump_stack+0x30/0x40 lib/dump_stack.c:88
 dump_stack_lvl+0xf4/0x15c lib/dump_stack.c:106
 dump_stack+0x1c/0x5c lib/dump_stack.c:113
 print_circular_bug+0x148/0x1b0 kernel/locking/lockdep.c:2088
 check_noncircular+0x290/0x370 kernel/locking/lockdep.c:2215
 check_prev_add kernel/locking/lockdep.c:3162 [inline]
 check_prevs_add kernel/locking/lockdep.c:3281 [inline]
 validate_chain kernel/locking/lockdep.c:3897 [inline]
 __lock_acquire+0x3504/0x7280 kernel/locking/lockdep.c:5171
 lock_acquire+0x210/0x63c kernel/locking/lockdep.c:5790
 __mutex_lock_common+0x1a0/0x1f3c kernel/locking/mutex.c:603
 __mutex_lock kernel/locking/mutex.c:747 [inline]
 mutex_lock_nested+0x38/0x44 kernel/locking/mutex.c:799
 rtnl_lock+0x20/0x2c net/core/rtnetlink.c:74
 wext_ioctl_dispatch+0xbc/0x3d0 net/wireless/wext-core.c:996
 wext_handle_ioctl+0x1ac/0x370 net/wireless/wext-core.c:1058
 sock_ioctl+0x138/0x828 net/socket.c:1253
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:870 [inline]
 __se_sys_ioctl fs/ioctl.c:856 [inline]
 __arm64_sys_ioctl+0x14c/0x1c8 fs/ioctl.c:856
 __invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
 invoke_syscall+0x98/0x290 arch/arm64/kernel/syscall.c:52
 el0_svc_common+0x13c/0x258 arch/arm64/kernel/syscall.c:140
 do_el0_svc+0x5c/0x134 arch/arm64/kernel/syscall.c:204
 el0_svc+0x58/0x12c arch/arm64/kernel/entry-common.c:637
 el0t_64_sync_handler+0x84/0xf0 arch/arm64/kernel/entry-common.c:655
 el0t_64_sync+0x18c/0x190 arch/arm64/kernel/entry.S:585

Crashes (4):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/10/03 17:21 linux-6.1.y a500ba24937a 57bbd979 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 possible deadlock in rtnl_lock
2026/10/03 16:55 linux-6.1.y a500ba24937a 57bbd979 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 possible deadlock in rtnl_lock
2026/10/03 13:50 linux-6.1.y a500ba24937a 57bbd979 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 possible deadlock in rtnl_lock
2026/10/03 13:48 linux-6.1.y a500ba24937a 57bbd979 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 possible deadlock in rtnl_lock
* Struck through repros no longer work on HEAD.