[syzbot] [wireless?] possible deadlock in ieee80211_remove_interfaces

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 431c1646e1f8 Linux 6.11-rc6
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=144a43db980000
kernel config: https://syzkaller.appspot.com/x/.config?x=931962fa28089080
dashboard link: https://syzkaller.appspot.com/bug?extid=5b9196ecf74447172a9a
compiler: gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image (non-bootable): https://storage.googleapis.com/syzbot-assets/7bc7510fe41f/non_bootable_disk-431c1646.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/01c0dadd39ff/vmlinux-431c1646.xz
kernel image: https://storage.googleapis.com/syzbot-assets/9e2259e440f7/bzImage-431c1646.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+5b9196...@syzkaller.appspotmail.com

======================================================
WARNING: possible circular locking dependency detected
6.11.0-rc6-syzkaller #0 Not tainted
------------------------------------------------------
kworker/u32:7/1108 is trying to acquire lock:
but task is already holding lock:
ffff888055278768 (&rdev->wiphy.mtx){+.+.}-{3:3}, at: wiphy_lock include/net/cfg80211.h:6014 [inline]
ffff888055278768 (&rdev->wiphy.mtx){+.+.}-{3:3}, at: ieee80211_remove_interfaces+0xfe/0x760 net/mac80211/iface.c:2262

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:
-> #1 (&rdev->wiphy.mtx){+.+.}-{3:3}:
dev_open net/core/dev.c:1510 [inline]
dev_open+0xf4/0x160 net/core/dev.c:1503
do_setlink+0xd24/0x4190 net/core/rtnetlink.c:2907
__rtnl_newlink+0xc35/0x1920 net/core/rtnetlink.c:3696
rtnl_newlink+0x67/0xa0 net/core/rtnetlink.c:3743
rtnetlink_rcv_msg+0x3c7/0xea0 net/core/rtnetlink.c:6647
netlink_rcv_skb+0x16b/0x440 net/netlink/af_netlink.c:2550
netlink_unicast_kernel net/netlink/af_netlink.c:1331 [inline]
netlink_unicast+0x53c/0x7f0 net/netlink/af_netlink.c:1357
netlink_sendmsg+0x8b8/0xd70 net/netlink/af_netlink.c:1901
entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #0 (team->team_lock_key#10){+.+.}-{3:3}:
check_prev_add kernel/locking/lockdep.c:3133 [inline]
check_prevs_add kernel/locking/lockdep.c:3252 [inline]
validate_chain kernel/locking/lockdep.c:3868 [inline]
__lock_acquire+0x24ed/0x3cb0 kernel/locking/lockdep.c:5142
lock_acquire kernel/locking/lockdep.c:5759 [inline]
lock_acquire+0x1b1/0x560 kernel/locking/lockdep.c:5724
__mutex_lock_common kernel/locking/mutex.c:608 [inline]
__mutex_lock+0x175/0x9c0 kernel/locking/mutex.c:752
team_del_slave+0x31/0x1b0 drivers/net/team/team_core.c:1990
team_device_event+0xd0/0x770 drivers/net/team/team_core.c:2984
notifier_call_chain+0xb9/0x410 kernel/notifier.c:93
call_netdevice_notifiers_info+0xbe/0x140 net/core/dev.c:1994
call_netdevice_notifiers_extack net/core/dev.c:2032 [inline]
call_netdevice_notifiers net/core/dev.c:2046 [inline]
unregister_netdevice_many_notify+0x8bb/0x1e40 net/core/dev.c:11352
mac80211_hwsim_del_radio drivers/net/wireless/virtual/mac80211_hwsim.c:5625 [inline]
hwsim_exit_net+0x3ad/0x7d0 drivers/net/wireless/virtual/mac80211_hwsim.c:6505
ops_exit_list+0xb0/0x180 net/core/net_namespace.c:173
cleanup_net+0x5b7/0xbb0 net/core/net_namespace.c:640
process_one_work+0x9c5/0x1b40 kernel/workqueue.c:3231
process_scheduled_works kernel/workqueue.c:3312 [inline]
worker_thread+0x6c8/0xed0 kernel/workqueue.c:3389
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
other info that might help us debug this:


---- ----
lock(&rdev->wiphy.mtx);
lock(team->team_lock_key#10);

*** DEADLOCK ***

5 locks held by kworker/u32:7/1108:
#0: ffff88801baf4948 ((wq_completion)netns){+.+.}-{0:0}, at: process_one_work+0x1277/0x1b40 kernel/workqueue.c:3206
stack backtrace:
CPU: 2 UID: 0 PID: 1108 Comm: kworker/u32:7 Not tainted 6.11.0-rc6-syzkaller #0
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014
Workqueue: netns cleanup_net
Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:93 [inline]
dump_stack_lvl+0x116/0x1f0 lib/dump_stack.c:119
check_noncircular+0x31a/0x400 kernel/locking/lockdep.c:2186
__mutex_lock_common kernel/locking/mutex.c:608 [inline]
__mutex_lock+0x175/0x9c0 kernel/locking/mutex.c:752
notifier_call_chain+0xb9/0x410 kernel/notifier.c:93
call_netdevice_notifiers_info+0xbe/0x140 net/core/dev.c:1994
call_netdevice_notifiers_extack net/core/dev.c:2032 [inline]
call_netdevice_notifiers net/core/dev.c:2046 [inline]
unregister_netdevice_many_notify+0x8bb/0x1e40 net/core/dev.c:11352
unregister_netdevice_many net/core/dev.c:11414 [inline]
unregister_netdevice_queue+0x307/0x3f0 net/core/dev.c:11289
unregister_netdevice include/linux/netdevice.h:3129 [inline]
_cfg80211_unregister_wdev+0x624/0x7f0 net/wireless/core.c:1211
ieee80211_remove_interfaces+0x36d/0x760 net/mac80211/iface.c:2287
ieee80211_unregister_hw+0x55/0x3a0 net/mac80211/main.c:1669
mac80211_hwsim_del_radio drivers/net/wireless/virtual/mac80211_hwsim.c:5625 [inline]
hwsim_exit_net+0x3ad/0x7d0 drivers/net/wireless/virtual/mac80211_hwsim.c:6505
process_scheduled_works kernel/workqueue.c:3312 [inline]
worker_thread+0x6c8/0xed0 kernel/workqueue.c:3389
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
</TASK>


---
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[syzbot]

syzbot has found a reproducer for the following issue on:

HEAD commit: 8d20dcda404d selftests: drv-net-hw: inject pp_alloc_fail e..
git tree: net-next
console output: https://syzkaller.appspot.com/x/log.txt?x=14ef5a18580000
kernel config: https://syzkaller.appspot.com/x/.config?x=c30f048a4f12891
dashboard link: https://syzkaller.appspot.com/bug?extid=5b9196ecf74447172a9a
compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=15d7a1f8580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/5ce07c743ced/disk-8d20dcda.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/66f2a9a35d5e/vmlinux-8d20dcda.xz
kernel image: https://storage.googleapis.com/syzbot-assets/4c790c086a46/bzImage-8d20dcda.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+5b9196...@syzkaller.appspotmail.com

======================================================
WARNING: possible circular locking dependency detected

6.13.0-rc7-syzkaller-01131-g8d20dcda404d #0 Not tainted
------------------------------------------------------
kworker/u8:6/3534 is trying to acquire lock:
ffffffff8fcb4a08 (rtnl_mutex){+.+.}-{4:4}, at: rtnl_acquire_if_cleanup_net net/core/dev.c:10281 [inline]
ffffffff8fcb4a08 (rtnl_mutex){+.+.}-{4:4}, at: unregister_netdevice_many_notify+0xac2/0x2030 net/core/dev.c:11783

but task is already holding lock:

ffff8880216b0768 (&rdev->wiphy.mtx){+.+.}-{4:4}, at: class_wiphy_constructor include/net/cfg80211.h:6034 [inline]
ffff8880216b0768 (&rdev->wiphy.mtx){+.+.}-{4:4}, at: ieee80211_remove_interfaces+0x129/0x700 net/mac80211/iface.c:2276

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #1 (&rdev->wiphy.mtx){+.+.}-{4:4}:
lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5849
__mutex_lock_common kernel/locking/mutex.c:585 [inline]
__mutex_lock+0x1ac/0xee0 kernel/locking/mutex.c:735
wiphy_lock include/net/cfg80211.h:6019 [inline]
wiphy_register+0x1a49/0x27b0 net/wireless/core.c:1006
ieee80211_register_hw+0x30fb/0x3e10 net/mac80211/main.c:1582
mac80211_hwsim_new_radio+0x2a9f/0x4a90 drivers/net/wireless/virtual/mac80211_hwsim.c:5558
init_mac80211_hwsim+0x87a/0xb00 drivers/net/wireless/virtual/mac80211_hwsim.c:6910
do_one_initcall+0x248/0x870 init/main.c:1266
do_initcall_level+0x157/0x210 init/main.c:1328
do_initcalls+0x3f/0x80 init/main.c:1344
kernel_init_freeable+0x435/0x5d0 init/main.c:1577
kernel_init+0x1d/0x2b0 init/main.c:1466
ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:147
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244

-> #0 (rtnl_mutex){+.+.}-{4:4}:
check_prev_add kernel/locking/lockdep.c:3161 [inline]
check_prevs_add kernel/locking/lockdep.c:3280 [inline]
validate_chain+0x18ef/0x5920 kernel/locking/lockdep.c:3904
__lock_acquire+0x1397/0x2100 kernel/locking/lockdep.c:5226
lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5849
__mutex_lock_common kernel/locking/mutex.c:585 [inline]
__mutex_lock+0x1ac/0xee0 kernel/locking/mutex.c:735
rtnl_acquire_if_cleanup_net net/core/dev.c:10281 [inline]
unregister_netdevice_many_notify+0xac2/0x2030 net/core/dev.c:11783
unregister_netdevice_many net/core/dev.c:11866 [inline]
unregister_netdevice_queue+0x303/0x370 net/core/dev.c:11732
unregister_netdevice include/linux/netdevice.h:3320 [inline]
_cfg80211_unregister_wdev+0x163/0x590 net/wireless/core.c:1251
ieee80211_remove_interfaces+0x4ef/0x700 net/mac80211/iface.c:2301
ieee80211_unregister_hw+0x5d/0x2c0 net/mac80211/main.c:1676
mac80211_hwsim_del_radio+0x2c4/0x4c0 drivers/net/wireless/virtual/mac80211_hwsim.c:5664
hwsim_exit_net+0x5c1/0x670 drivers/net/wireless/virtual/mac80211_hwsim.c:6544
ops_exit_list net/core/net_namespace.c:172 [inline]
cleanup_net+0x812/0xd60 net/core/net_namespace.c:652
process_one_work kernel/workqueue.c:3236 [inline]
process_scheduled_works+0xa66/0x1840 kernel/workqueue.c:3317
worker_thread+0x870/0xd30 kernel/workqueue.c:3398
kthread+0x2f0/0x390 kernel/kthread.c:389
ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:147

ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244

other info that might help us debug this:

Possible unsafe locking scenario:

CPU0 CPU1
---- ----
lock(&rdev->wiphy.mtx);
lock(rtnl_mutex);
lock(&rdev->wiphy.mtx);
lock(rtnl_mutex);

*** DEADLOCK ***

4 locks held by kworker/u8:6/3534:
#0: ffff88801baf5948 ((wq_completion)netns){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3211 [inline]
#0: ffff88801baf5948 ((wq_completion)netns){+.+.}-{0:0}, at: process_scheduled_works+0x93b/0x1840 kernel/workqueue.c:3317
#1: ffffc9000d507d00 (net_cleanup_work){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3212 [inline]
#1: ffffc9000d507d00 (net_cleanup_work){+.+.}-{0:0}, at: process_scheduled_works+0x976/0x1840 kernel/workqueue.c:3317
#2: ffffffff8fca8290 (pernet_ops_rwsem){++++}-{4:4}, at: cleanup_net+0x17a/0xd60 net/core/net_namespace.c:606
#3: ffff8880216b0768 (&rdev->wiphy.mtx){+.+.}-{4:4}, at: class_wiphy_constructor include/net/cfg80211.h:6034 [inline]
#3: ffff8880216b0768 (&rdev->wiphy.mtx){+.+.}-{4:4}, at: ieee80211_remove_interfaces+0x129/0x700 net/mac80211/iface.c:2276

stack backtrace:
CPU: 1 UID: 0 PID: 3534 Comm: kworker/u8:6 Not tainted 6.13.0-rc7-syzkaller-01131-g8d20dcda404d #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 12/27/2024

Workqueue: netns cleanup_net
Call Trace:
<TASK>

__dump_stack lib/dump_stack.c:94 [inline]
dump_stack_lvl+0x241/0x360 lib/dump_stack.c:120
print_circular_bug+0x13a/0x1b0 kernel/locking/lockdep.c:2074
check_noncircular+0x36a/0x4a0 kernel/locking/lockdep.c:2206
check_prev_add kernel/locking/lockdep.c:3161 [inline]
check_prevs_add kernel/locking/lockdep.c:3280 [inline]
validate_chain+0x18ef/0x5920 kernel/locking/lockdep.c:3904
__lock_acquire+0x1397/0x2100 kernel/locking/lockdep.c:5226
lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5849
__mutex_lock_common kernel/locking/mutex.c:585 [inline]
__mutex_lock+0x1ac/0xee0 kernel/locking/mutex.c:735
rtnl_acquire_if_cleanup_net net/core/dev.c:10281 [inline]
unregister_netdevice_many_notify+0xac2/0x2030 net/core/dev.c:11783
unregister_netdevice_many net/core/dev.c:11866 [inline]
unregister_netdevice_queue+0x303/0x370 net/core/dev.c:11732
unregister_netdevice include/linux/netdevice.h:3320 [inline]
_cfg80211_unregister_wdev+0x163/0x590 net/wireless/core.c:1251
ieee80211_remove_interfaces+0x4ef/0x700 net/mac80211/iface.c:2301
ieee80211_unregister_hw+0x5d/0x2c0 net/mac80211/main.c:1676
mac80211_hwsim_del_radio+0x2c4/0x4c0 drivers/net/wireless/virtual/mac80211_hwsim.c:5664
hwsim_exit_net+0x5c1/0x670 drivers/net/wireless/virtual/mac80211_hwsim.c:6544
ops_exit_list net/core/net_namespace.c:172 [inline]
cleanup_net+0x812/0xd60 net/core/net_namespace.c:652
process_one_work kernel/workqueue.c:3236 [inline]
process_scheduled_works+0xa66/0x1840 kernel/workqueue.c:3317
worker_thread+0x870/0xd30 kernel/workqueue.c:3398
kthread+0x2f0/0x390 kernel/kthread.c:389
ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:147
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
</TASK>
hsr_slave_0: left promiscuous mode
hsr_slave_1: left promiscuous mode
batman_adv: batadv0: Interface deactivated: batadv_slave_0
batman_adv: batadv0: Removing interface: batadv_slave_0
batman_adv: batadv0: Interface deactivated: batadv_slave_1
batman_adv: batadv0: Removing interface: batadv_slave_1
veth1_macvtap: left promiscuous mode
veth0_macvtap: left promiscuous mode
veth1_vlan: left promiscuous mode
veth0_vlan: left promiscuous mode
team0 (unregistering): Port device team_slave_1 removed
team0 (unregistering): Port device team_slave_0 removed
bridge0: port 2(bridge_slave_1) entered blocking state
bridge0: port 2(bridge_slave_1) entered forwarding state
bridge0: port 1(bridge_slave_0) entered blocking state
bridge0: port 1(bridge_slave_0) entered forwarding state
bridge0: port 2(bridge_slave_1) entered blocking state
bridge0: port 2(bridge_slave_1) entered forwarding state


---
If you want syzbot to run the reproducer, reply with:
#syz test: git://repo/address.git branch-or-commit-hash
If you attach or paste a git patch, syzbot will apply it before testing.

[Eric Dumazet]

This repro is for another bug I think, caused by my recent commits in net-next:

83419b61d187ce22aa3da5ffdda850fca3a12600 net: reduce RTNL hold
duration in unregister_netdevice_many_notify() (part 2)
ae646f1a0bb97401bac0044bbe2a179a1e38b408 net: reduce RTNL hold
duration in unregister_netdevice_many_notify() (part 1)
cfa579f6665635b72d4a075fc91eb144c2b0f74e net: no longer hold RTNL
while calling flush_all_backlogs()

cleanup_net()
rtnl_lock();
mutex_lock(subsystem_mutex);

unregister_netdevice();

rtnl_unlock(); // LOCKDEP violation
rtnl_lock();

I will work today on a fix, auditing all unregister_netdevice() and
unregister_netdevice_many()
and select which of them can safely opt-in for a variant which _can_
temporarily release RTNL.

[syzbot]

syzbot has found a reproducer for the following issue on:

HEAD commit: 8d20dcda404d selftests: drv-net-hw: inject pp_alloc_fail e..
git tree: net-next

console output: https://syzkaller.appspot.com/x/log.txt?x=13ff9fc4580000
kernel config: https://syzkaller.appspot.com/x/.config?x=c30f048a4f12891
dashboard link: https://syzkaller.appspot.com/bug?extid=5b9196ecf74447172a9a
compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=17ff9fc4580000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=13ca3a18580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/5ce07c743ced/disk-8d20dcda.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/66f2a9a35d5e/vmlinux-8d20dcda.xz
kernel image: https://storage.googleapis.com/syzbot-assets/4c790c086a46/bzImage-8d20dcda.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+5b9196...@syzkaller.appspotmail.com

bond0 (unregistering): (slave bond_slave_0): Releasing backup interface
bond0 (unregistering): (slave bond_slave_1): Releasing backup interface
bond0 (unregistering): Released all slaves

======================================================
WARNING: possible circular locking dependency detected

6.13.0-rc7-syzkaller-01131-g8d20dcda404d #0 Not tainted
------------------------------------------------------

kworker/u8:6/1143 is trying to acquire lock:

ffffffff8fcb4a08 (rtnl_mutex){+.+.}-{4:4}, at: rtnl_acquire_if_cleanup_net net/core/dev.c:10281 [inline]
ffffffff8fcb4a08 (rtnl_mutex){+.+.}-{4:4}, at: unregister_netdevice_many_notify+0xac2/0x2030 net/core/dev.c:11783

but task is already holding lock:

ffff888027260768 (&rdev->wiphy.mtx){+.+.}-{4:4}, at: class_wiphy_constructor include/net/cfg80211.h:6034 [inline]
ffff888027260768 (&rdev->wiphy.mtx){+.+.}-{4:4}, at: ieee80211_remove_interfaces+0x129/0x700 net/mac80211/iface.c:2276

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #1 (&rdev->wiphy.mtx){+.+.}-{4:4}:
lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5849
__mutex_lock_common kernel/locking/mutex.c:585 [inline]
__mutex_lock+0x1ac/0xee0 kernel/locking/mutex.c:735
wiphy_lock include/net/cfg80211.h:6019 [inline]
wiphy_register+0x1a49/0x27b0 net/wireless/core.c:1006
ieee80211_register_hw+0x30fb/0x3e10 net/mac80211/main.c:1582
mac80211_hwsim_new_radio+0x2a9f/0x4a90 drivers/net/wireless/virtual/mac80211_hwsim.c:5558
init_mac80211_hwsim+0x87a/0xb00 drivers/net/wireless/virtual/mac80211_hwsim.c:6910
do_one_initcall+0x248/0x870 init/main.c:1266
do_initcall_level+0x157/0x210 init/main.c:1328
do_initcalls+0x3f/0x80 init/main.c:1344
kernel_init_freeable+0x435/0x5d0 init/main.c:1577
kernel_init+0x1d/0x2b0 init/main.c:1466

ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:147
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244

-> #0 (rtnl_mutex){+.+.}-{4:4}:
check_prev_add kernel/locking/lockdep.c:3161 [inline]
check_prevs_add kernel/locking/lockdep.c:3280 [inline]
validate_chain+0x18ef/0x5920 kernel/locking/lockdep.c:3904
__lock_acquire+0x1397/0x2100 kernel/locking/lockdep.c:5226
lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5849
__mutex_lock_common kernel/locking/mutex.c:585 [inline]
__mutex_lock+0x1ac/0xee0 kernel/locking/mutex.c:735
rtnl_acquire_if_cleanup_net net/core/dev.c:10281 [inline]
unregister_netdevice_many_notify+0xac2/0x2030 net/core/dev.c:11783
unregister_netdevice_many net/core/dev.c:11866 [inline]
unregister_netdevice_queue+0x303/0x370 net/core/dev.c:11732
unregister_netdevice include/linux/netdevice.h:3320 [inline]
_cfg80211_unregister_wdev+0x163/0x590 net/wireless/core.c:1251
ieee80211_remove_interfaces+0x4ef/0x700 net/mac80211/iface.c:2301
ieee80211_unregister_hw+0x5d/0x2c0 net/mac80211/main.c:1676
mac80211_hwsim_del_radio+0x2c4/0x4c0 drivers/net/wireless/virtual/mac80211_hwsim.c:5664
hwsim_exit_net+0x5c1/0x670 drivers/net/wireless/virtual/mac80211_hwsim.c:6544
ops_exit_list net/core/net_namespace.c:172 [inline]
cleanup_net+0x812/0xd60 net/core/net_namespace.c:652
process_one_work kernel/workqueue.c:3236 [inline]
process_scheduled_works+0xa66/0x1840 kernel/workqueue.c:3317
worker_thread+0x870/0xd30 kernel/workqueue.c:3398
kthread+0x2f0/0x390 kernel/kthread.c:389

ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:147

ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244

other info that might help us debug this:

Possible unsafe locking scenario:

CPU0 CPU1
---- ----
lock(&rdev->wiphy.mtx);
lock(rtnl_mutex);
lock(&rdev->wiphy.mtx);
lock(rtnl_mutex);

*** DEADLOCK ***

4 locks held by kworker/u8:6/1143:

#0: ffff88801baf5948 ((wq_completion)netns){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3211 [inline]

#0: ffff88801baf5948 ((wq_completion)netns){+.+.}-{0:0}, at: process_scheduled_works+0x93b/0x1840 kernel/workqueue.c:3317
#1: ffffc900041ffd00 (net_cleanup_work){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3212 [inline]
#1: ffffc900041ffd00 (net_cleanup_work){+.+.}-{0:0}, at: process_scheduled_works+0x976/0x1840 kernel/workqueue.c:3317

#2: ffffffff8fca8290 (pernet_ops_rwsem){++++}-{4:4}, at: cleanup_net+0x17a/0xd60 net/core/net_namespace.c:606

#3: ffff888027260768 (&rdev->wiphy.mtx){+.+.}-{4:4}, at: class_wiphy_constructor include/net/cfg80211.h:6034 [inline]
#3: ffff888027260768 (&rdev->wiphy.mtx){+.+.}-{4:4}, at: ieee80211_remove_interfaces+0x129/0x700 net/mac80211/iface.c:2276

stack backtrace:
CPU: 0 UID: 0 PID: 1143 Comm: kworker/u8:6 Not tainted 6.13.0-rc7-syzkaller-01131-g8d20dcda404d #0

Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 12/27/2024

Workqueue: netns cleanup_net
Call Trace:
<TASK>

ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:147

ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
</TASK>


---

[Hillf Danton]

On Fri, 17 Jan 2025 11:07:25 -0800

> syzbot has found a reproducer for the following issue on:
>
> HEAD commit: 8d20dcda404d selftests: drv-net-hw: inject pp_alloc_fail e..
> git tree: net-next

> C reproducer: https://syzkaller.appspot.com/x/repro.c?x=13ca3a18580000

#syz test

diff -pur p/include/linux/netdevice.h q/include/linux/netdevice.h
--- p/include/linux/netdevice.h 2025-01-19 14:23:21.962713400 +0800
+++ q/include/linux/netdevice.h 2025-01-19 14:44:32.303599900 +0800
@@ -2047,6 +2047,7 @@ enum netdev_reg_state {
* FIXME: cleanup struct net_device such that network protocol info
* moves out.
*/
+extern unsigned long extra_netdev_locks;

struct net_device {
/* Cacheline organization can be found documented in
diff -pur p/net/core/dev.c q/net/core/dev.c
--- p/net/core/dev.c 2025-01-19 14:26:04.863348200 +0800
+++ q/net/core/dev.c 2025-01-19 14:35:42.722041700 +0800
@@ -10269,14 +10269,19 @@ static bool from_cleanup_net(void)
#endif
}

+unsigned long extra_netdev_locks = 0;
static void rtnl_drop_if_cleanup_net(void)
{
+ if (extra_netdev_locks)
+ return;
if (from_cleanup_net())
__rtnl_unlock();
}

static void rtnl_acquire_if_cleanup_net(void)
{
+ if (extra_netdev_locks)
+ return;
if (from_cleanup_net())
rtnl_lock();
}
diff -pur p/net/wireless/core.c q/net/wireless/core.c
--- p/net/wireless/core.c 2025-01-19 14:29:30.497265000 +0800
+++ q/net/wireless/core.c 2025-01-19 14:40:07.687903000 +0800
@@ -1247,8 +1247,11 @@ static void _cfg80211_unregister_wdev(st

if (wdev->netdev) {
sysfs_remove_link(&wdev->netdev->dev.kobj, "phy80211");
- if (unregister_netdev)
+ if (unregister_netdev) {
+ extra_netdev_locks++;
unregister_netdevice(wdev->netdev);
+ extra_netdev_locks--;
+ }
}

list_del_rcu(&wdev->list);
--

[syzbot]

Hello,

syzbot has tested the proposed patch and the reproducer did not trigger any issue:

Reported-by: syzbot+5b9196...@syzkaller.appspotmail.com
Tested-by: syzbot+5b9196...@syzkaller.appspotmail.com

Tested on:

commit: 59372af6 Merge tag 'batadv-next-pullrequest-20250117' ..
git tree: net-next
console output: https://syzkaller.appspot.com/x/log.txt?x=137b6164580000

kernel config: https://syzkaller.appspot.com/x/.config?x=c30f048a4f12891
dashboard link: https://syzkaller.appspot.com/bug?extid=5b9196ecf74447172a9a
compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40

patch: https://syzkaller.appspot.com/x/patch.diff?x=17f2e2b0580000

Note: testing is done by a robot and is best-effort only.

[Aleksandr Nogikh]

Hi Eric,

Could you please share what's the current situation with the fix?
The bug unfortunately keeps on stalling the fuzzing on syzbot by
causing 70+% of all daily crashes.

--
Aleksandr

[Eric Dumazet]

On Tue, Jan 28, 2025 at 7:13 PM Aleksandr Nogikh <nog...@google.com> wrote:
>
> Hi Eric,

>
>
> Could you please share what's the current situation with the fix?
> The bug unfortunately keeps on stalling the fuzzing on syzbot by
> causing 70+% of all daily crashes.

I think I am going to send a revert for the net tree, and revisit this
stuff for the next cycle.