[syzbot] [fs?] [wireless?] general protection fault in simple_recursive_removal (5)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 89be9a83ccf1 Linux 6.16-rc7
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=11b42fd4580000
kernel config: https://syzkaller.appspot.com/x/.config?x=8adfe52da0de2761
dashboard link: https://syzkaller.appspot.com/bug?extid=d6ccd49ae046542a0641
compiler: Debian clang version 20.1.7 (++20250616065708+6146a88f6049-1~exp1~20250616065826.132), Debian LLD 20.1.7
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=134baf22580000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=16d5a4f0580000

Downloadable assets:
disk image (non-bootable): https://storage.googleapis.com/syzbot-assets/d900f083ada3/non_bootable_disk-89be9a83.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/a3f5f507f252/vmlinux-89be9a83.xz
kernel image: https://storage.googleapis.com/syzbot-assets/a8f9b92c57a6/bzImage-89be9a83.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+d6ccd4...@syzkaller.appspotmail.com

wlan1: send auth to aa:09:b7:99:c0:d7 (try 2/3)
wlan1: send auth to aa:09:b7:99:c0:d7 (try 3/3)
wlan1: authentication with aa:09:b7:99:c0:d7 timed out
Oops: general protection fault, probably for non-canonical address 0xdffffc0000000029: 0000 [#1] SMP KASAN NOPTI
KASAN: null-ptr-deref in range [0x0000000000000148-0x000000000000014f]
CPU: 0 UID: 0 PID: 171 Comm: kworker/u4:4 Not tainted 6.16.0-rc7-syzkaller #0 PREEMPT(full)
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014
Workqueue: events_unbound cfg80211_wiphy_work
RIP: 0010:kasan_byte_accessible+0x12/0x30 mm/kasan/generic.c:199
Code: 0f 1f 84 00 00 00 00 00 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 66 0f 1f 00 48 c1 ef 03 48 b8 00 00 00 00 00 fc ff df <0f> b6 04 07 3c 08 0f 92 c0 c3 cc cc cc cc cc 66 66 66 66 66 66 2e
RSP: 0018:ffffc90001977400 EFLAGS: 00010202
RAX: dffffc0000000000 RBX: ffffffff8b713286 RCX: ca5c1933e35f3700
RDX: 0000000000000000 RSI: ffffffff8b713286 RDI: 0000000000000029
RBP: ffffffff824067f0 R08: 0000000000000001 R09: 0000000000000000
R10: dffffc0000000000 R11: ffffed10085cf24c R12: 0000000000000000
R13: 0000000000000148 R14: 0000000000000148 R15: 0000000000000001
FS: 0000000000000000(0000) GS:ffff88808d218000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000001b2f55ffff CR3: 000000005030a000 CR4: 0000000000352ef0
Call Trace:
<TASK>
__kasan_check_byte+0x12/0x40 mm/kasan/common.c:556
kasan_check_byte include/linux/kasan.h:399 [inline]
lock_acquire+0x8d/0x360 kernel/locking/lockdep.c:5845
down_write+0x96/0x1f0 kernel/locking/rwsem.c:1577
inode_lock include/linux/fs.h:869 [inline]
simple_recursive_removal+0x90/0x690 fs/libfs.c:616
debugfs_remove+0x5b/0x70 fs/debugfs/inode.c:805
ieee80211_sta_debugfs_remove+0x40/0x70 net/mac80211/debugfs_sta.c:1279
__sta_info_destroy_part2+0x352/0x450 net/mac80211/sta_info.c:1501
__sta_info_destroy net/mac80211/sta_info.c:1517 [inline]
sta_info_destroy_addr+0xf5/0x140 net/mac80211/sta_info.c:1529
ieee80211_destroy_auth_data+0x12d/0x260 net/mac80211/mlme.c:4597
ieee80211_sta_work+0x11cf/0x3600 net/mac80211/mlme.c:8310
cfg80211_wiphy_work+0x2df/0x460 net/wireless/core.c:435
process_one_work kernel/workqueue.c:3238 [inline]
process_scheduled_works+0xae1/0x17b0 kernel/workqueue.c:3321
worker_thread+0x8a0/0xda0 kernel/workqueue.c:3402
kthread+0x70e/0x8a0 kernel/kthread.c:464
ret_from_fork+0x3fc/0x770 arch/x86/kernel/process.c:148
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
</TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:kasan_byte_accessible+0x12/0x30 mm/kasan/generic.c:199
Code: 0f 1f 84 00 00 00 00 00 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 66 0f 1f 00 48 c1 ef 03 48 b8 00 00 00 00 00 fc ff df <0f> b6 04 07 3c 08 0f 92 c0 c3 cc cc cc cc cc 66 66 66 66 66 66 2e
RSP: 0018:ffffc90001977400 EFLAGS: 00010202
RAX: dffffc0000000000 RBX: ffffffff8b713286 RCX: ca5c1933e35f3700
RDX: 0000000000000000 RSI: ffffffff8b713286 RDI: 0000000000000029
RBP: ffffffff824067f0 R08: 0000000000000001 R09: 0000000000000000
R10: dffffc0000000000 R11: ffffed10085cf24c R12: 0000000000000000
R13: 0000000000000148 R14: 0000000000000148 R15: 0000000000000001
FS: 0000000000000000(0000) GS:ffff88808d218000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000001b2f55ffff CR3: 0000000011601000 CR4: 0000000000352ef0
----------------
Code disassembly (best guess):
0: 0f 1f 84 00 00 00 00 nopl 0x0(%rax,%rax,1)
7: 00
8: 90 nop
9: 90 nop
a: 90 nop
b: 90 nop
c: 90 nop
d: 90 nop
e: 90 nop
f: 90 nop
10: 90 nop
11: 90 nop
12: 90 nop
13: 90 nop
14: 90 nop
15: 90 nop
16: 90 nop
17: 90 nop
18: 66 0f 1f 00 nopw (%rax)
1c: 48 c1 ef 03 shr $0x3,%rdi
20: 48 b8 00 00 00 00 00 movabs $0xdffffc0000000000,%rax
27: fc ff df
* 2a: 0f b6 04 07 movzbl (%rdi,%rax,1),%eax <-- trapping instruction
2e: 3c 08 cmp $0x8,%al
30: 0f 92 c0 setb %al
33: c3 ret
34: cc int3
35: cc int3
36: cc int3
37: cc int3
38: cc int3
39: 66 data16
3a: 66 data16
3b: 66 data16
3c: 66 data16
3d: 66 data16
3e: 66 data16
3f: 2e cs


---
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If the report is already addressed, let syzbot know by replying with:
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#syz undup

[Hillf Danton]

> Date: Wed, 23 Jul 2025 10:19:28 -0700 [thread overview]

> Hello,
>
> syzbot found the following issue on:
>
> HEAD commit: 89be9a83ccf1 Linux 6.16-rc7
> git tree: upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=11b42fd4580000
> kernel config: https://syzkaller.appspot.com/x/.config?x=8adfe52da0de2761
> dashboard link: https://syzkaller.appspot.com/bug?extid=d6ccd49ae046542a0641

> syz repro: https://syzkaller.appspot.com/x/repro.syz?x=134baf22580000
> C reproducer: https://syzkaller.appspot.com/x/repro.c?x=16d5a4f0580000

#syz test

--- x/net/mac80211/debugfs_sta.c
+++ y/net/mac80211/debugfs_sta.c
@@ -1276,6 +1276,8 @@ void ieee80211_sta_debugfs_add(struct st

void ieee80211_sta_debugfs_remove(struct sta_info *sta)
{
+ if (!sta->debugfs_dir)
+ return;
debugfs_remove_recursive(sta->debugfs_dir);
sta->debugfs_dir = NULL;
}
--

[syzbot]

Hello,

syzbot has tested the proposed patch but the reproducer is still triggering an issue:
KASAN: slab-use-after-free Read in lockref_get

wlan1: send auth to aa:09:b7:99:c0:d7 (try 2/3)
wlan1: send auth to aa:09:b7:99:c0:d7 (try 3/3)
wlan1: authentication with aa:09:b7:99:c0:d7 timed out

==================================================================
BUG: KASAN: slab-use-after-free in __raw_spin_lock include/linux/spinlock_api_smp.h:133 [inline]
BUG: KASAN: slab-use-after-free in _raw_spin_lock+0x2e/0x40 kernel/locking/spinlock.c:154
Read of size 1 at addr ffff888042a47b40 by task kworker/u4:4/169

CPU: 0 UID: 0 PID: 169 Comm: kworker/u4:4 Not tainted 6.16.0-rc7-syzkaller-gf9af7b5d9349-dirty #0 PREEMPT(full)

Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014
Workqueue: events_unbound cfg80211_wiphy_work

Call Trace:
<TASK>
dump_stack_lvl+0x189/0x250 lib/dump_stack.c:120
print_address_description mm/kasan/report.c:378 [inline]
print_report+0xca/0x230 mm/kasan/report.c:480
kasan_report+0x118/0x150 mm/kasan/report.c:593
__kasan_check_byte+0x2a/0x40 mm/kasan/common.c:557

kasan_check_byte include/linux/kasan.h:399 [inline]
lock_acquire+0x8d/0x360 kernel/locking/lockdep.c:5845

__raw_spin_lock include/linux/spinlock_api_smp.h:133 [inline]
_raw_spin_lock+0x2e/0x40 kernel/locking/spinlock.c:154
spin_lock include/linux/spinlock.h:351 [inline]
lockref_get+0x15/0x60 lib/lockref.c:50
dget include/linux/dcache.h:345 [inline]
simple_recursive_removal+0x35/0x690 fs/libfs.c:611
debugfs_remove+0x5b/0x70 fs/debugfs/inode.c:805
ieee80211_sta_debugfs_remove+0x4f/0x80 net/mac80211/debugfs_sta.c:1281

__sta_info_destroy_part2+0x352/0x450 net/mac80211/sta_info.c:1501
__sta_info_destroy net/mac80211/sta_info.c:1517 [inline]
sta_info_destroy_addr+0xf5/0x140 net/mac80211/sta_info.c:1529
ieee80211_destroy_auth_data+0x12d/0x260 net/mac80211/mlme.c:4597
ieee80211_sta_work+0x11cf/0x3600 net/mac80211/mlme.c:8310

cfg80211_wiphy_work+0x2dc/0x460 net/wireless/core.c:435

process_one_work kernel/workqueue.c:3238 [inline]
process_scheduled_works+0xae1/0x17b0 kernel/workqueue.c:3321
worker_thread+0x8a0/0xda0 kernel/workqueue.c:3402
kthread+0x70e/0x8a0 kernel/kthread.c:464
ret_from_fork+0x3fc/0x770 arch/x86/kernel/process.c:148
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
</TASK>

Allocated by task 5860:
kasan_save_stack mm/kasan/common.c:47 [inline]
kasan_save_track+0x3e/0x80 mm/kasan/common.c:68
unpoison_slab_object mm/kasan/common.c:319 [inline]
__kasan_slab_alloc+0x6c/0x80 mm/kasan/common.c:345
kasan_slab_alloc include/linux/kasan.h:250 [inline]
slab_post_alloc_hook mm/slub.c:4148 [inline]
slab_alloc_node mm/slub.c:4197 [inline]
kmem_cache_alloc_lru_noprof+0x1c6/0x3d0 mm/slub.c:4216
__d_alloc+0x31/0x6f0 fs/dcache.c:1690
d_alloc fs/dcache.c:1769 [inline]
d_alloc_parallel+0xe0/0x14e0 fs/dcache.c:2533
__lookup_slow+0x116/0x3d0 fs/namei.c:1802
start_creating+0x22e/0x3c0 fs/debugfs/inode.c:391
debugfs_create_dir+0x28/0x420 fs/debugfs/inode.c:586
ieee80211_sta_debugfs_add+0x12c/0x850 net/mac80211/debugfs_sta.c:1254
sta_info_insert_finish net/mac80211/sta_info.c:892 [inline]
sta_info_insert_rcu+0xfac/0x1940 net/mac80211/sta_info.c:960
sta_info_insert+0x16/0xc0 net/mac80211/sta_info.c:965
ieee80211_prep_connection+0x10cd/0x1600 net/mac80211/mlme.c:8854
ieee80211_mgd_auth+0xee3/0x1770 net/mac80211/mlme.c:9119
rdev_auth net/wireless/rdev-ops.h:486 [inline]
cfg80211_mlme_auth+0x62f/0x9c0 net/wireless/mlme.c:291
cfg80211_conn_do_work+0x501/0xd10 net/wireless/sme.c:183
cfg80211_sme_connect net/wireless/sme.c:626 [inline]
cfg80211_connect+0x1862/0x21a0 net/wireless/sme.c:1525
nl80211_connect+0x17bc/0x1cd0 net/wireless/nl80211.c:12303
genl_family_rcv_msg_doit+0x215/0x300 net/netlink/genetlink.c:1115
genl_family_rcv_msg net/netlink/genetlink.c:1195 [inline]
genl_rcv_msg+0x60e/0x790 net/netlink/genetlink.c:1210
netlink_rcv_skb+0x205/0x470 net/netlink/af_netlink.c:2552
genl_rcv+0x28/0x40 net/netlink/genetlink.c:1219
netlink_unicast_kernel net/netlink/af_netlink.c:1320 [inline]
netlink_unicast+0x75c/0x8e0 net/netlink/af_netlink.c:1346
netlink_sendmsg+0x805/0xb30 net/netlink/af_netlink.c:1896
sock_sendmsg_nosec net/socket.c:712 [inline]
__sock_sendmsg+0x219/0x270 net/socket.c:727
____sys_sendmsg+0x505/0x830 net/socket.c:2566
___sys_sendmsg+0x21f/0x2a0 net/socket.c:2620
__sys_sendmsg net/socket.c:2652 [inline]
__do_sys_sendmsg net/socket.c:2657 [inline]
__se_sys_sendmsg net/socket.c:2655 [inline]
__x64_sys_sendmsg+0x19b/0x260 net/socket.c:2655
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xfa/0x3b0 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

Freed by task 15:
kasan_save_stack mm/kasan/common.c:47 [inline]
kasan_save_track+0x3e/0x80 mm/kasan/common.c:68
kasan_save_free_info+0x46/0x50 mm/kasan/generic.c:576
poison_slab_object mm/kasan/common.c:247 [inline]
__kasan_slab_free+0x62/0x70 mm/kasan/common.c:264
kasan_slab_free include/linux/kasan.h:233 [inline]
slab_free_hook mm/slub.c:2381 [inline]
slab_free mm/slub.c:4643 [inline]
kmem_cache_free+0x18f/0x400 mm/slub.c:4745
rcu_do_batch kernel/rcu/tree.c:2576 [inline]
rcu_core+0xca5/0x1710 kernel/rcu/tree.c:2832
handle_softirqs+0x286/0x870 kernel/softirq.c:579
run_ksoftirqd+0x9b/0x100 kernel/softirq.c:968
smpboot_thread_fn+0x53f/0xa60 kernel/smpboot.c:164

kthread+0x70e/0x8a0 kernel/kthread.c:464
ret_from_fork+0x3fc/0x770 arch/x86/kernel/process.c:148
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

Last potentially related work creation:
kasan_save_stack+0x3e/0x60 mm/kasan/common.c:47
kasan_record_aux_stack+0xbd/0xd0 mm/kasan/generic.c:548
__call_rcu_common kernel/rcu/tree.c:3094 [inline]
call_rcu+0x157/0x9c0 kernel/rcu/tree.c:3214
__dentry_kill+0x4d2/0x660 fs/dcache.c:688
dput+0x19f/0x2b0 fs/dcache.c:911
find_next_child+0x1e5/0x250 fs/libfs.c:603
simple_recursive_removal+0xf4/0x690 fs/libfs.c:619
debugfs_remove+0x5b/0x70 fs/debugfs/inode.c:805
ieee80211_debugfs_remove_netdev net/mac80211/debugfs_netdev.c:1021 [inline]
ieee80211_debugfs_recreate_netdev+0xbf/0x1460 net/mac80211/debugfs_netdev.c:1034
drv_remove_interface+0x1fa/0x590 net/mac80211/driver-ops.c:125
_ieee80211_change_mac net/mac80211/iface.c:277 [inline]
ieee80211_change_mac+0x912/0x12c0 net/mac80211/iface.c:309
netif_set_mac_address+0x2fc/0x4c0 net/core/dev.c:9688
do_setlink+0x88c/0x41c0 net/core/rtnetlink.c:3093
rtnl_changelink net/core/rtnetlink.c:3759 [inline]
__rtnl_newlink net/core/rtnetlink.c:3918 [inline]
rtnl_newlink+0x160b/0x1c70 net/core/rtnetlink.c:4055
rtnetlink_rcv_msg+0x7cc/0xb70 net/core/rtnetlink.c:6944
netlink_rcv_skb+0x205/0x470 net/netlink/af_netlink.c:2552
netlink_unicast_kernel net/netlink/af_netlink.c:1320 [inline]
netlink_unicast+0x75c/0x8e0 net/netlink/af_netlink.c:1346
netlink_sendmsg+0x805/0xb30 net/netlink/af_netlink.c:1896
sock_sendmsg_nosec net/socket.c:712 [inline]
__sock_sendmsg+0x219/0x270 net/socket.c:727
____sys_sendmsg+0x505/0x830 net/socket.c:2566
___sys_sendmsg+0x21f/0x2a0 net/socket.c:2620
__sys_sendmsg net/socket.c:2652 [inline]
__do_sys_sendmsg net/socket.c:2657 [inline]
__se_sys_sendmsg net/socket.c:2655 [inline]
__x64_sys_sendmsg+0x19b/0x260 net/socket.c:2655
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xfa/0x3b0 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

The buggy address belongs to the object at ffff888042a47a70
which belongs to the cache dentry of size 312
The buggy address is located 208 bytes inside of
freed 312-byte region [ffff888042a47a70, ffff888042a47ba8)

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x42a46
head: order:1 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0
memcg:ffff88803ff67101
flags: 0x4fff00000000040(head|node=1|zone=1|lastcpupid=0x7ff)
page_type: f5(slab)
raw: 04fff00000000040 ffff88801b6db780 dead000000000100 dead000000000122
raw: 0000000000000000 0000000000150015 00000000f5000000 ffff88803ff67101
head: 04fff00000000040 ffff88801b6db780 dead000000000100 dead000000000122
head: 0000000000000000 0000000000150015 00000000f5000000 ffff88803ff67101
head: 04fff00000000001 ffffea00010a9181 00000000ffffffff 00000000ffffffff
head: ffffffffffffffff 0000000000000000 00000000ffffffff 0000000000000002
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 1, migratetype Reclaimable, gfp_mask 0xd20d0(__GFP_RECLAIMABLE|__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 4739, tgid 4739 (udevd), ts 37957937697, free_ts 0
set_page_owner include/linux/page_owner.h:32 [inline]
post_alloc_hook+0x240/0x2a0 mm/page_alloc.c:1704
prep_new_page mm/page_alloc.c:1712 [inline]
get_page_from_freelist+0x21e4/0x22c0 mm/page_alloc.c:3669
__alloc_frozen_pages_noprof+0x181/0x370 mm/page_alloc.c:4959
alloc_pages_mpol+0x232/0x4a0 mm/mempolicy.c:2419
alloc_slab_page mm/slub.c:2451 [inline]
allocate_slab+0x8a/0x3b0 mm/slub.c:2619
new_slab mm/slub.c:2673 [inline]
___slab_alloc+0xbfc/0x1480 mm/slub.c:3859
__slab_alloc mm/slub.c:3949 [inline]
__slab_alloc_node mm/slub.c:4024 [inline]
slab_alloc_node mm/slub.c:4185 [inline]
kmem_cache_alloc_lru_noprof+0x288/0x3d0 mm/slub.c:4216
__d_alloc+0x31/0x6f0 fs/dcache.c:1690
d_alloc fs/dcache.c:1769 [inline]
d_alloc_parallel+0xe0/0x14e0 fs/dcache.c:2533
lookup_open fs/namei.c:3639 [inline]
open_last_lookups fs/namei.c:3816 [inline]
path_openat+0xa3b/0x3830 fs/namei.c:4052
do_filp_open+0x1fa/0x410 fs/namei.c:4082
do_sys_openat2+0x121/0x1c0 fs/open.c:1437
do_sys_open fs/open.c:1452 [inline]
__do_sys_openat fs/open.c:1468 [inline]
__se_sys_openat fs/open.c:1463 [inline]
__x64_sys_openat+0x138/0x170 fs/open.c:1463
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xfa/0x3b0 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
page_owner free stack trace missing

Memory state around the buggy address:
ffff888042a47a00: 00 00 00 00 00 00 fc fc fc fc fc fc fc fc fa fb
ffff888042a47a80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff888042a47b00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff888042a47b80: fb fb fb fb fb fc fc fc fc fc fc fc fc 00 00 00
ffff888042a47c00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
==================================================================


Tested on:

commit: f9af7b5d Merge tag 'for-linus' of git://git.kernel.org..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=174640a2580000

kernel config: https://syzkaller.appspot.com/x/.config?x=8adfe52da0de2761
dashboard link: https://syzkaller.appspot.com/bug?extid=d6ccd49ae046542a0641

compiler: Debian clang version 20.1.7 (++20250616065708+6146a88f6049-1~exp1~20250616065826.132), Debian LLD 20.1.7

patch: https://syzkaller.appspot.com/x/patch.diff?x=151a40a2580000

[Hillf Danton]

> Date: Wed, 23 Jul 2025 10:19:28 -0700 [thread overview]

> Hello,
>
> syzbot found the following issue on:
>
> HEAD commit: 89be9a83ccf1 Linux 6.16-rc7
> git tree: upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=11b42fd4580000
> kernel config: https://syzkaller.appspot.com/x/.config?x=8adfe52da0de2761
> dashboard link: https://syzkaller.appspot.com/bug?extid=d6ccd49ae046542a0641

> syz repro: https://syzkaller.appspot.com/x/repro.syz?x=134baf22580000
> C reproducer: https://syzkaller.appspot.com/x/repro.c?x=16d5a4f0580000

#syz test

--- x/net/mac80211/debugfs_sta.c
+++ y/net/mac80211/debugfs_sta.c

@@ -1276,6 +1276,12 @@ void ieee80211_sta_debugfs_add(struct st

void ieee80211_sta_debugfs_remove(struct sta_info *sta)
{
+ struct dentry *stations_dir = sta->sdata->debugfs.subdir_stations;
+
+ if (!stations_dir)
+ return;

[syzbot]

Hello,

syzbot has tested the proposed patch but the reproducer is still triggering an issue:
KASAN: slab-use-after-free Read in lockref_get

wlan1: send auth to aa:09:b7:99:c0:d7 (try 2/3)
wlan1: send auth to aa:09:b7:99:c0:d7 (try 3/3)
wlan1: authentication with aa:09:b7:99:c0:d7 timed out
==================================================================
BUG: KASAN: slab-use-after-free in __raw_spin_lock include/linux/spinlock_api_smp.h:133 [inline]
BUG: KASAN: slab-use-after-free in _raw_spin_lock+0x2e/0x40 kernel/locking/spinlock.c:154

Read of size 1 at addr ffff888042ff76d8 by task kworker/u4:0/12

CPU: 0 UID: 0 PID: 12 Comm: kworker/u4:0 Not tainted 6.16.0-rc7-syzkaller-g25fae0b93d1d-dirty #0 PREEMPT(full)

Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014
Workqueue: events_unbound cfg80211_wiphy_work
Call Trace:
<TASK>
dump_stack_lvl+0x189/0x250 lib/dump_stack.c:120
print_address_description mm/kasan/report.c:378 [inline]
print_report+0xca/0x230 mm/kasan/report.c:480
kasan_report+0x118/0x150 mm/kasan/report.c:593
__kasan_check_byte+0x2a/0x40 mm/kasan/common.c:557
kasan_check_byte include/linux/kasan.h:399 [inline]
lock_acquire+0x8d/0x360 kernel/locking/lockdep.c:5845
__raw_spin_lock include/linux/spinlock_api_smp.h:133 [inline]
_raw_spin_lock+0x2e/0x40 kernel/locking/spinlock.c:154
spin_lock include/linux/spinlock.h:351 [inline]
lockref_get+0x15/0x60 lib/lockref.c:50
dget include/linux/dcache.h:345 [inline]
simple_recursive_removal+0x35/0x690 fs/libfs.c:611
debugfs_remove+0x5b/0x70 fs/debugfs/inode.c:805

ieee80211_sta_debugfs_remove+0x8e/0xc0 net/mac80211/debugfs_sta.c:1285

__sta_info_destroy_part2+0x352/0x450 net/mac80211/sta_info.c:1501
__sta_info_destroy net/mac80211/sta_info.c:1517 [inline]
sta_info_destroy_addr+0xf5/0x140 net/mac80211/sta_info.c:1529
ieee80211_destroy_auth_data+0x12d/0x260 net/mac80211/mlme.c:4597
ieee80211_sta_work+0x11cf/0x3600 net/mac80211/mlme.c:8310

cfg80211_wiphy_work+0x2df/0x460 net/wireless/core.c:435

process_one_work kernel/workqueue.c:3238 [inline]
process_scheduled_works+0xae1/0x17b0 kernel/workqueue.c:3321
worker_thread+0x8a0/0xda0 kernel/workqueue.c:3402
kthread+0x70e/0x8a0 kernel/kthread.c:464
ret_from_fork+0x3fc/0x770 arch/x86/kernel/process.c:148
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
</TASK>

Allocated by task 5867:

kasan_save_stack mm/kasan/common.c:47 [inline]
kasan_save_track+0x3e/0x80 mm/kasan/common.c:68
unpoison_slab_object mm/kasan/common.c:319 [inline]
__kasan_slab_alloc+0x6c/0x80 mm/kasan/common.c:345
kasan_slab_alloc include/linux/kasan.h:250 [inline]
slab_post_alloc_hook mm/slub.c:4148 [inline]
slab_alloc_node mm/slub.c:4197 [inline]
kmem_cache_alloc_lru_noprof+0x1c6/0x3d0 mm/slub.c:4216
__d_alloc+0x31/0x6f0 fs/dcache.c:1690
d_alloc fs/dcache.c:1769 [inline]
d_alloc_parallel+0xe0/0x14e0 fs/dcache.c:2533
__lookup_slow+0x116/0x3d0 fs/namei.c:1802
start_creating+0x22e/0x3c0 fs/debugfs/inode.c:391
debugfs_create_dir+0x28/0x420 fs/debugfs/inode.c:586
ieee80211_sta_debugfs_add+0x12c/0x850 net/mac80211/debugfs_sta.c:1254
sta_info_insert_finish net/mac80211/sta_info.c:892 [inline]
sta_info_insert_rcu+0xfac/0x1940 net/mac80211/sta_info.c:960
sta_info_insert+0x16/0xc0 net/mac80211/sta_info.c:965
ieee80211_prep_connection+0x10cd/0x1600 net/mac80211/mlme.c:8854
ieee80211_mgd_auth+0xee3/0x1770 net/mac80211/mlme.c:9119
rdev_auth net/wireless/rdev-ops.h:486 [inline]

cfg80211_mlme_auth+0x632/0x9c0 net/wireless/mlme.c:291

cfg80211_conn_do_work+0x501/0xd10 net/wireless/sme.c:183
cfg80211_sme_connect net/wireless/sme.c:626 [inline]
cfg80211_connect+0x1862/0x21a0 net/wireless/sme.c:1525
nl80211_connect+0x17bc/0x1cd0 net/wireless/nl80211.c:12303

genl_family_rcv_msg_doit+0x212/0x300 net/netlink/genetlink.c:1115

genl_family_rcv_msg net/netlink/genetlink.c:1195 [inline]
genl_rcv_msg+0x60e/0x790 net/netlink/genetlink.c:1210

netlink_rcv_skb+0x208/0x470 net/netlink/af_netlink.c:2552

genl_rcv+0x28/0x40 net/netlink/genetlink.c:1219
netlink_unicast_kernel net/netlink/af_netlink.c:1320 [inline]

netlink_unicast+0x759/0x8e0 net/netlink/af_netlink.c:1346

netlink_sendmsg+0x805/0xb30 net/netlink/af_netlink.c:1896
sock_sendmsg_nosec net/socket.c:712 [inline]

__sock_sendmsg+0x21c/0x270 net/socket.c:727

netif_set_mac_address+0x2f9/0x4c0 net/core/dev.c:9688

do_setlink+0x88c/0x41c0 net/core/rtnetlink.c:3093
rtnl_changelink net/core/rtnetlink.c:3759 [inline]
__rtnl_newlink net/core/rtnetlink.c:3918 [inline]
rtnl_newlink+0x160b/0x1c70 net/core/rtnetlink.c:4055

rtnetlink_rcv_msg+0x7cf/0xb70 net/core/rtnetlink.c:6944
netlink_rcv_skb+0x208/0x470 net/netlink/af_netlink.c:2552
netlink_unicast_kernel net/netlink/af_netlink.c:1320 [inline]
netlink_unicast+0x759/0x8e0 net/netlink/af_netlink.c:1346

netlink_sendmsg+0x805/0xb30 net/netlink/af_netlink.c:1896
sock_sendmsg_nosec net/socket.c:712 [inline]

__sock_sendmsg+0x21c/0x270 net/socket.c:727

____sys_sendmsg+0x505/0x830 net/socket.c:2566
___sys_sendmsg+0x21f/0x2a0 net/socket.c:2620
__sys_sendmsg net/socket.c:2652 [inline]
__do_sys_sendmsg net/socket.c:2657 [inline]
__se_sys_sendmsg net/socket.c:2655 [inline]
__x64_sys_sendmsg+0x19b/0x260 net/socket.c:2655
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xfa/0x3b0 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

The buggy address belongs to the object at ffff888042ff7608

which belongs to the cache dentry of size 312
The buggy address is located 208 bytes inside of

freed 312-byte region [ffff888042ff7608, ffff888042ff7740)

The buggy address belongs to the physical page:

page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x42ff6

head: order:1 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0

memcg:ffff88803440e501
ksm flags: 0x4fff00000000040(head|node=1|zone=1|lastcpupid=0x7ff)
page_type: f5(slab)
raw: 04fff00000000040 ffff888030413780 ffffea00010c1d00 dead000000000003
raw: 0000000000000000 0000000000150015 00000000f5000000 ffff88803440e501
head: 04fff00000000040 ffff888030413780 ffffea00010c1d00 dead000000000003
head: 0000000000000000 0000000000150015 00000000f5000000 ffff88803440e501
head: 04fff00000000001 ffffea00010bfd81 00000000ffffffff 00000000ffffffff

head: ffffffffffffffff 0000000000000000 00000000ffffffff 0000000000000002
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated

page last allocated via order 1, migratetype Reclaimable, gfp_mask 0xd20d0(__GFP_RECLAIMABLE|__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 4744, tgid 4744 (udevd), ts 37683151774, free_ts 0

ffff888042ff7580: fb fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc
ffff888042ff7600: fc fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff888042ff7680: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff888042ff7700: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
ffff888042ff7780: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================


Tested on:

commit: 25fae0b9 Merge tag 'drm-fixes-2025-07-24' of https://g..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1357dfd4580000

kernel config: https://syzkaller.appspot.com/x/.config?x=8adfe52da0de2761
dashboard link: https://syzkaller.appspot.com/bug?extid=d6ccd49ae046542a0641

compiler: Debian clang version 20.1.7 (++20250616065708+6146a88f6049-1~exp1~20250616065826.132), Debian LLD 20.1.7

patch: https://syzkaller.appspot.com/x/patch.diff?x=15c140a2580000

[Moon Hee Lee]

#syz test git://git.kernel.org/pub/scm/linux/kernel/git/wireless/wireless-next.git
main

[syzbot]

> #syz test git://git.kernel.org/pub/scm/linux/kernel/git/wireless/wireless-next.git

want either no args or 2 args (repo, branch), got 1

> main

[Moon Hee Lee]

[syzbot]

[Moon Hee Lee]

#syz test git://git.kernel.org/pub/scm/linux/kernel/git/wireless/wireless-next.git main

A NULL pointer dereference may occur in ieee80211_sta_debugfs_remove()
when debugfs_remove_recursive() is called on a dentry whose inode has
already been freed. This can happen due to a race between STA teardown
and debugfs cleanup.

Fix this by checking that both sta->debugfs_dir and its d_inode are
valid before invoking debugfs_remove_recursive().

This avoids the crash reported in syzbot bug:

wlan1: send auth to aa:09:b7:99:c0:d7 (try 2/3)
wlan1: send auth to aa:09:b7:99:c0:d7 (try 3/3)
wlan1: authentication with aa:09:b7:99:c0:d7 timed out

Oops: general protection fault, probably for non-canonical address 0xdffffc0000000029: 0000 [#1] SMP KASAN NOPTI
KASAN: null-ptr-deref in range [0x0000000000000148-0x000000000000014f]

CPU: 0 UID: 0 PID: 171 Comm: kworker/u4:4 Not tainted 6.16.0-rc7-syzkaller #0 PREEMPT(full)

Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014
Workqueue: events_unbound cfg80211_wiphy_work

RIP: 0010:kasan_byte_accessible+0x12/0x30 mm/kasan/generic.c:199
Code: 0f 1f 84 00 00 00 00 00 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 66 0f 1f 00 48 c1 ef 03 48 b8 00 00 00 00 00 fc ff df <0f> b6 04 07 3c 08 0f 92 c0 c3 cc cc cc cc cc 66 66 66 66 66 66 2e
RSP: 0018:ffffc90001977400 EFLAGS: 00010202
RAX: dffffc0000000000 RBX: ffffffff8b713286 RCX: ca5c1933e35f3700
RDX: 0000000000000000 RSI: ffffffff8b713286 RDI: 0000000000000029
RBP: ffffffff824067f0 R08: 0000000000000001 R09: 0000000000000000
R10: dffffc0000000000 R11: ffffed10085cf24c R12: 0000000000000000
R13: 0000000000000148 R14: 0000000000000148 R15: 0000000000000001
FS: 0000000000000000(0000) GS:ffff88808d218000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000001b2f55ffff CR3: 000000005030a000 CR4: 0000000000352ef0
Call Trace:
<TASK>
__kasan_check_byte+0x12/0x40 mm/kasan/common.c:556

kasan_check_byte include/linux/kasan.h:399 [inline]
lock_acquire+0x8d/0x360 kernel/locking/lockdep.c:5845

down_write+0x96/0x1f0 kernel/locking/rwsem.c:1577
inode_lock include/linux/fs.h:869 [inline]
simple_recursive_removal+0x90/0x690 fs/libfs.c:616
debugfs_remove+0x5b/0x70 fs/debugfs/inode.c:805
ieee80211_sta_debugfs_remove+0x40/0x70 net/mac80211/debugfs_sta.c:1279

__sta_info_destroy_part2+0x352/0x450 net/mac80211/sta_info.c:1501
__sta_info_destroy net/mac80211/sta_info.c:1517 [inline]
sta_info_destroy_addr+0xf5/0x140 net/mac80211/sta_info.c:1529
ieee80211_destroy_auth_data+0x12d/0x260 net/mac80211/mlme.c:4597
ieee80211_sta_work+0x11cf/0x3600 net/mac80211/mlme.c:8310
cfg80211_wiphy_work+0x2df/0x460 net/wireless/core.c:435
process_one_work kernel/workqueue.c:3238 [inline]
process_scheduled_works+0xae1/0x17b0 kernel/workqueue.c:3321
worker_thread+0x8a0/0xda0 kernel/workqueue.c:3402
kthread+0x70e/0x8a0 kernel/kthread.c:464
ret_from_fork+0x3fc/0x770 arch/x86/kernel/process.c:148
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
</TASK>

---
net/mac80211/debugfs_sta.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/net/mac80211/debugfs_sta.c b/net/mac80211/debugfs_sta.c
index 49061bd4151b..912b69abab52 100644
--- a/net/mac80211/debugfs_sta.c
+++ b/net/mac80211/debugfs_sta.c
@@ -1276,7 +1276,8 @@ void ieee80211_sta_debugfs_add(struct sta_info *sta)

void ieee80211_sta_debugfs_remove(struct sta_info *sta)
{
- debugfs_remove_recursive(sta->debugfs_dir);
+ if (sta->debugfs_dir && sta->debugfs_dir->d_inode)
+ debugfs_remove_recursive(sta->debugfs_dir);

sta->debugfs_dir = NULL;
}

--

2.43.0

[syzbot]

Hello,

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

Reported-by: syzbot+d6ccd4...@syzkaller.appspotmail.com
Tested-by: syzbot+d6ccd4...@syzkaller.appspotmail.com

Tested on:

commit: 3630f043 Merge tag 'iwlwifi-next-2025-07-23' of https:..
git tree: git://git.kernel.org/pub/scm/linux/kernel/git/wireless/wireless-next.git main
console output: https://syzkaller.appspot.com/x/log.txt?x=16a740a2580000
kernel config: https://syzkaller.appspot.com/x/.config?x=51ebcb9cd994f900

dashboard link: https://syzkaller.appspot.com/bug?extid=d6ccd49ae046542a0641
compiler: Debian clang version 20.1.7 (++20250616065708+6146a88f6049-1~exp1~20250616065826.132), Debian LLD 20.1.7

patch: https://syzkaller.appspot.com/x/patch.diff?x=1449d0a2580000

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

[Hillf Danton]

> Date: Wed, 23 Jul 2025 10:19:28 -0700 [thread overview]

> Hello,
>
> syzbot found the following issue on:
>
> HEAD commit: 89be9a83ccf1 Linux 6.16-rc7
> git tree: upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=11b42fd4580000
> kernel config: https://syzkaller.appspot.com/x/.config?x=8adfe52da0de2761
> dashboard link: https://syzkaller.appspot.com/bug?extid=d6ccd49ae046542a0641

> syz repro: https://syzkaller.appspot.com/x/repro.syz?x=134baf22580000
> C reproducer: https://syzkaller.appspot.com/x/repro.c?x=16d5a4f0580000

#syz test

--- x/net/mac80211/sta_info.h
+++ y/net/mac80211/sta_info.h
@@ -705,7 +705,7 @@ struct sta_info {
struct sta_ampdu_mlme ampdu_mlme;

#ifdef CONFIG_MAC80211_DEBUGFS
- struct dentry *debugfs_dir;
+ struct dentry *debugfs_dir, *pd;
#endif

u8 reserved_tid;
--- x/net/mac80211/debugfs_sta.c
+++ y/net/mac80211/debugfs_sta.c
@@ -1252,6 +1252,7 @@ void ieee80211_sta_debugfs_add(struct st
* dir might still be around.
*/
sta->debugfs_dir = debugfs_create_dir(mac, stations_dir);
+ sta->pd = stations_dir;

DEBUGFS_ADD(flags);
DEBUGFS_ADD(aid);
@@ -1276,7 +1277,14 @@ void ieee80211_sta_debugfs_add(struct st

void ieee80211_sta_debugfs_remove(struct sta_info *sta)
{
- debugfs_remove_recursive(sta->debugfs_dir);

+ struct dentry *stations_dir = sta->sdata->debugfs.subdir_stations;
+

+ if (!sta->debugfs_dir)
+ return;

+ if (!stations_dir)
+ return;

+ if (sta->pd == stations_dir)

[syzbot]

Hello,

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

Reported-by: syzbot+d6ccd4...@syzkaller.appspotmail.com
Tested-by: syzbot+d6ccd4...@syzkaller.appspotmail.com

Tested on:

commit: 25fae0b9 Merge tag 'drm-fixes-2025-07-24' of https://g..

git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=10f13fd4580000

kernel config: https://syzkaller.appspot.com/x/.config?x=8adfe52da0de2761
dashboard link: https://syzkaller.appspot.com/bug?extid=d6ccd49ae046542a0641

compiler: Debian clang version 20.1.7 (++20250616065708+6146a88f6049-1~exp1~20250616065826.132), Debian LLD 20.1.7

patch: https://syzkaller.appspot.com/x/patch.diff?x=12e13fd4580000

[Al Viro]

On Wed, Jul 23, 2025 at 11:40:52PM -0700, Moon Hee Lee wrote:
> #syz test git://git.kernel.org/pub/scm/linux/kernel/git/wireless/wireless-next.git main
>
> A NULL pointer dereference may occur in ieee80211_sta_debugfs_remove()
> when debugfs_remove_recursive() is called on a dentry whose inode has
> already been freed. This can happen due to a race between STA teardown
> and debugfs cleanup.
>
> Fix this by checking that both sta->debugfs_dir and its d_inode are
> valid before invoking debugfs_remove_recursive().

> void ieee80211_sta_debugfs_remove(struct sta_info *sta)
> {
> - debugfs_remove_recursive(sta->debugfs_dir);
> + if (sta->debugfs_dir && sta->debugfs_dir->d_inode)
> + debugfs_remove_recursive(sta->debugfs_dir);
> sta->debugfs_dir = NULL;
> }

It might paper over the specific reproducer, but that's not a fix...
I'm not familiar with that code; will check the details, but in
this form it is obviously still racy.

NAK.

[Moon Hee Lee]

On Thu, Jul 24, 2025 at 8:58 AM Al Viro <vi...@zeniv.linux.org.uk> wrote:
> It might paper over the specific reproducer, but that's not a fix...
> I'm not familiar with that code; will check the details, but in
> this form it is obviously still racy.

Thanks for the feedback, Al.

Agreed, this only papers over the issue. I'm tracing the
sta_info_destroy() path to confirm the race and will follow up with a
proper fix if confirmed.

--
moon

[Hillf Danton]

A look at net/mac80211/debugfs_netdev.c:1021 [1] helps to prepare a proper fix.

[1] https://lore.kernel.org/lkml/6881aed3.a00a022...@google.com/

[Al Viro]

Note that if you have nested subtrees, you have to be very careful
about removals - after all, removal of the bigger one drops the
references we are holding to the roots of the smaller ones.

[Moon Hee Lee]

#syz test git://git.kernel.org/pub/scm/linux/kernel/git/wireless/wireless-next.git main

Thanks for the review and valuable feedback.

Upon investigation, I found the crash occurs when the netdev's debugfs
directory is removed while a station still holds a pointer
(sta->debugfs_dir) to a dentry within it. A subsequent call to
ieee80211_sta_debugfs_remove() may then dereference a freed dentry,
triggering a use-after-free.

To address this, I’m preparing a patch that clears sta->debugfs_dir for
all stations associated with the interface before calling
debugfs_remove_recursive(). This ensures any later station removal
becomes a no-op and avoids referencing a stale pointer.

This reply is intended for syz testing and to provide context for
review. A formal patch will follow.

Many thanks to Hillf Danton and Al Viro for their insights.

---
net/mac80211/debugfs_netdev.c | 15 +++++++++++++++
1 file changed, 15 insertions(+)

diff --git a/net/mac80211/debugfs_netdev.c b/net/mac80211/debugfs_netdev.c
index 1dac78271045..4d45bb4fe380 100644
--- a/net/mac80211/debugfs_netdev.c
+++ b/net/mac80211/debugfs_netdev.c
@@ -1015,9 +1015,24 @@ static void ieee80211_debugfs_add_netdev(struct ieee80211_sub_if_data *sdata,

void ieee80211_debugfs_remove_netdev(struct ieee80211_sub_if_data *sdata)
{
+ struct sta_info *sta;
+
if (!sdata->vif.debugfs_dir)
return;

+ /*
+ * Before we delete the netdev’s debugfs tree, clear sta->debugfs_dir
+ * for every station on this interface. This ensures any later call to
+ * ieee80211_sta_debugfs_remove() sees NULL and avoids touching a dentry
+ * that we are about to free.
+ */
+ rcu_read_lock();
+ list_for_each_entry_rcu(sta, &sdata->local->sta_list, list) {
+ if (sta->sdata == sdata)
+ sta->debugfs_dir = NULL;
+ }
+ rcu_read_unlock();
+
debugfs_remove_recursive(sdata->vif.debugfs_dir);
sdata->vif.debugfs_dir = NULL;
sdata->debugfs.subdir_stations = NULL;
--
2.43.0

[Al Viro]

On Thu, Jul 31, 2025 at 10:17:29AM -0700, Moon Hee Lee wrote:
> #syz test git://git.kernel.org/pub/scm/linux/kernel/git/wireless/wireless-next.git main
>
>
> Thanks for the review and valuable feedback.
>
> Upon investigation, I found the crash occurs when the netdev's debugfs
> directory is removed while a station still holds a pointer
> (sta->debugfs_dir) to a dentry within it. A subsequent call to
> ieee80211_sta_debugfs_remove() may then dereference a freed dentry,
> triggering a use-after-free.
>
> To address this, I’m preparing a patch that clears sta->debugfs_dir for
> all stations associated with the interface before calling
> debugfs_remove_recursive(). This ensures any later station removal
> becomes a no-op and avoids referencing a stale pointer.
>
> This reply is intended for syz testing and to provide context for
> review. A formal patch will follow.

> + /*
> + * Before we delete the netdev’s debugfs tree, clear sta->debugfs_dir
> + * for every station on this interface. This ensures any later call to
> + * ieee80211_sta_debugfs_remove() sees NULL and avoids touching a dentry
> + * that we are about to free.
> + */
> + rcu_read_lock();
> + list_for_each_entry_rcu(sta, &sdata->local->sta_list, list) {
> + if (sta->sdata == sdata)
> + sta->debugfs_dir = NULL;
> + }
> + rcu_read_unlock();

Umm... Is there any exclusion between that an ieee80211_sta_debugfs_remove()?
This looks fishy...

[syzbot]

Hello,

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

Reported-by: syzbot+d6ccd4...@syzkaller.appspotmail.com
Tested-by: syzbot+d6ccd4...@syzkaller.appspotmail.com

Tested on:

commit: 126d85fb Merge tag 'wireless-next-2025-07-24' of https..

git tree: git://git.kernel.org/pub/scm/linux/kernel/git/wireless/wireless-next.git main

console output: https://syzkaller.appspot.com/x/log.txt?x=1104acf0580000
kernel config: https://syzkaller.appspot.com/x/.config?x=4e0aa2ee2717f461

dashboard link: https://syzkaller.appspot.com/bug?extid=d6ccd49ae046542a0641
compiler: Debian clang version 20.1.7 (++20250616065708+6146a88f6049-1~exp1~20250616065826.132), Debian LLD 20.1.7

patch: https://syzkaller.appspot.com/x/patch.diff?x=128ee9bc580000

[syzbot]

Auto-closing this bug as obsolete.
No recent activity, existing reproducers are no longer triggering the issue.