[syzbot] [wireless?] KASAN: slab-use-after-free Read in tasklet_action_common

[syzbot] [wireless?] KASAN: slab-use-after-free Read in tasklet_action_common

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit:    d24e8ac715de Merge tag 'net-7.3-rc6' of git://git.kernel.o..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=14361b15580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=9d4242cb1c54cdf7
dashboard link: https://syzkaller.appspot.com/bug?extid=e91dc13b1b37759b3d9f
compiler:       Debian clang version 22.1.8 (++20260613092233+e80beda6e255-1~exp1~20260613092250.77), Debian LLD 22.1.8
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=12361b15580000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=155bc725580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/4ccd4fb94f0b/disk-d24e8ac7.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/701ac3e3f73b/vmlinux-d24e8ac7.xz
kernel image: https://storage.googleapis.com/syzbot-assets/976b7d839ef2/bzImage-d24e8ac7.xz

The issue was bisected to:

commit 1af8dc9ca726cf53767f9c0661171396f95c146a
Author: Toke Høiland-Jørgensen <toke@redhat.com>
Date:   Tue Sep 8 17:05:18 2026 +0000

    wifi: ath9k: Clean up device initialisation guards

bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=145e5b15580000
final oops:     https://syzkaller.appspot.com/x/report.txt?x=165e5b15580000
console output: https://syzkaller.appspot.com/x/log.txt?x=125e5b15580000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+e91dc13b1b37759b3d9f@syzkaller.appspotmail.com
Fixes: 1af8dc9ca726 ("wifi: ath9k: Clean up device initialisation guards")

==================================================================
BUG: KASAN: slab-use-after-free in tasklet_action_common+0x103/0x490 kernel/softirq.c:954
Read of size 8 at addr ffff888035947158 by task syz-executor/5756

CPU: 0 UID: 0 PID: 5756 Comm: syz-executor Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
Call Trace:
 <IRQ>
 dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120
 print_address_description+0x55/0x1e0 mm/kasan/report.c:378
 print_report+0x58/0x70 mm/kasan/report.c:482
 kasan_report+0x117/0x150 mm/kasan/report.c:595
 tasklet_action_common+0x103/0x490 kernel/softirq.c:954
 handle_softirqs+0x226/0x860 kernel/softirq.c:645
 do_softirq+0x77/0xd0 kernel/softirq.c:546
 </IRQ>
 <TASK>
 __local_bh_enable_ip+0x100/0x140 kernel/softirq.c:473
 spin_unlock_bh include/linux/spinlock.h:407 [inline]
 tun_flow_delete_by_queue drivers/net/tun.c:379 [inline]
 __tun_detach+0xccc/0x1900 drivers/net/tun.c:614
 tun_detach drivers/net/tun.c:653 [inline]
 tun_chr_close+0x10a/0x1c0 drivers/net/tun.c:3587
 __fput+0x418/0xa50 fs/file_table.c:512
 task_work_run+0x1d9/0x270 kernel/task_work.c:233
 exit_task_work include/linux/task_work.h:40 [inline]
 do_exit+0x73a/0x2360 kernel/exit.c:986
 do_group_exit+0x22d/0x2f0 kernel/exit.c:1129
 __do_sys_exit_group kernel/exit.c:1140 [inline]
 __se_sys_exit_group kernel/exit.c:1138 [inline]
 __x64_sys_exit_group+0x3f/0x40 kernel/exit.c:1138
 x64_sys_call+0x18c6/0x18d0 arch/x86/include/generated/asm/syscalls_64.h:232
 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
 do_syscall_64+0x166/0x520 arch/x86/entry/syscall_64.c:84
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f558db9e159
Code: Unable to access opcode bytes at 0x7f558db9e12f.
RSP: 002b:00007ffc01d96c68 EFLAGS: 00000246 ORIG_RAX: 00000000000000e7
RAX: ffffffffffffffda RBX: 00007f558dc35fb3 RCX: 00007f558db9e159
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000043
RBP: 00007f558dc35fc5 R08: 0000000000000000 R09: 00000000000927c0
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000006
R13: 00000000000927c0 R14: 0000000000015771 R15: 00007ffc01d96e10
 </TASK>

Allocated by task 9:
 kasan_save_stack mm/kasan/common.c:57 [inline]
 kasan_save_track+0x3e/0x80 mm/kasan/common.c:78
 poison_kmalloc_redzone mm/kasan/common.c:409 [inline]
 __kasan_kmalloc+0x93/0xb0 mm/kasan/common.c:426
 kasan_kmalloc include/linux/kasan.h:263 [inline]
 __kmalloc_cache_noprof+0x321/0x600 mm/slub.c:5563
 _kmalloc_noprof include/linux/slab.h:991 [inline]
 _kzalloc_noprof include/linux/slab.h:1312 [inline]
 ath9k_init_wmi+0x4f/0x2b0 drivers/net/wireless/ath/ath9k/wmi.c:95
 ath9k_htc_probe_device+0x1e5/0x2370 drivers/net/wireless/ath/ath9k/htc_drv_init.c:956
 ath9k_htc_hw_init+0x32/0x70 drivers/net/wireless/ath/ath9k/htc_hst.c:532
 ath9k_hif_usb_firmware_cb+0x214/0x4b0 drivers/net/wireless/ath/ath9k/hif_usb.c:1255
 request_firmware_work_func+0xf7/0x2d0 drivers/base/firmware_loader/main.c:1164
 process_one_work kernel/workqueue.c:3396 [inline]
 process_scheduled_works+0xc3d/0x1630 kernel/workqueue.c:3479
 worker_thread+0xa47/0xfb0 kernel/workqueue.c:3560
 kthread+0x38b/0x480 kernel/kthread.c:436
 ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

Freed by task 9:
 kasan_save_stack mm/kasan/common.c:57 [inline]
 kasan_save_track+0x3e/0x80 mm/kasan/common.c:78
 kasan_save_free_info+0x40/0x50 mm/kasan/generic.c:584
 poison_slab_object mm/kasan/common.c:264 [inline]
 __kasan_slab_free+0x5c/0x80 mm/kasan/common.c:296
 kasan_slab_free include/linux/kasan.h:235 [inline]
 slab_free_hook mm/slub.c:2748 [inline]
 slab_free mm/slub.c:6508 [inline]
 kfree+0x1c5/0x650 mm/slub.c:6801
 ath9k_htc_probe_device+0x11a9/0x2370 drivers/net/wireless/ath/ath9k/htc_drv_init.c:978
 ath9k_htc_hw_init+0x32/0x70 drivers/net/wireless/ath/ath9k/htc_hst.c:532
 ath9k_hif_usb_firmware_cb+0x214/0x4b0 drivers/net/wireless/ath/ath9k/hif_usb.c:1255
 request_firmware_work_func+0xf7/0x2d0 drivers/base/firmware_loader/main.c:1164
 process_one_work kernel/workqueue.c:3396 [inline]
 process_scheduled_works+0xc3d/0x1630 kernel/workqueue.c:3479
 worker_thread+0xa47/0xfb0 kernel/workqueue.c:3560
 kthread+0x38b/0x480 kernel/kthread.c:436
 ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

The buggy address belongs to the object at ffff888035947000
 which belongs to the cache kmalloc-2k of size 2048
The buggy address is located 344 bytes inside of
 freed 2048-byte region [ffff888035947000, ffff888035947800)

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x35940
head: order:3 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0
flags: 0xfff00000000040(head|node=0|zone=1|lastcpupid=0x7ff)
page_type: f5(slab)
raw: 00fff00000000040 ffff88801b042000 dead000000000100 dead000000000122
raw: 0000000000000000 0000000000080008 00000000f5000000 0000000000000000
head: 00fff00000000040 ffff88801b042000 dead000000000100 dead000000000122
head: 0000000000000000 0000000000080008 00000000f5000000 0000000000000000
head: 00fff00000000003 fffffffffffffe01 00000000ffffffff 00000000ffffffff
head: ffffffffffffffff 0000000000000000 00000000ffffffff 0000000000000008
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 3, migratetype Unmovable, gfp_mask 0xd20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 1225, tgid 1225 (kworker/0:2), ts 87487181723
 set_page_owner include/linux/page_owner.h:33 [inline]
 post_alloc_hook+0x1f9/0x250 mm/page_alloc.c:1871
 prep_new_page mm/page_alloc.c:1879 [inline]
 get_page_from_freelist+0x2209/0x2280 mm/page_alloc.c:3943
 __alloc_frozen_pages_noprof+0x217/0x5a0 mm/page_alloc.c:5436
 alloc_slab_page mm/slub.c:3347 [inline]
 allocate_slab+0x7d/0x620 mm/slub.c:3462
 new_slab mm/slub.c:3513 [inline]
 refill_objects+0x2d5/0x350 mm/slub.c:7417
 refill_sheaf mm/slub.c:2885 [inline]
 __pcs_replace_empty_main+0x2c8/0x6c0 mm/slub.c:4774
 alloc_from_pcs mm/slub.c:4850 [inline]
 slab_alloc_node mm/slub.c:4984 [inline]
 __do_kmalloc_node mm/slub.c:5413 [inline]
 __kmalloc_node_track_caller_noprof+0x548/0x720 mm/slub.c:5545
 kmalloc_reserve net/core/skbuff.c:637 [inline]
 __alloc_skb+0x2c1/0x7a0 net/core/skbuff.c:715
 alloc_skb include/linux/skbuff.h:1384 [inline]
 mld_newpack+0x165/0xcb0 net/ipv6/mcast.c:1810
 add_grhead net/ipv6/mcast.c:1921 [inline]
 add_grec+0x119f/0x19d0 net/ipv6/mcast.c:2060
 mld_send_initial_cr+0x288/0x550 net/ipv6/mcast.c:2305
 mld_dad_work+0x3d/0x480 net/ipv6/mcast.c:2331
 process_one_work kernel/workqueue.c:3396 [inline]
 process_scheduled_works+0xc3d/0x1630 kernel/workqueue.c:3479
 worker_thread+0xa47/0xfb0 kernel/workqueue.c:3560
 kthread+0x38b/0x480 kernel/kthread.c:436
 ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158
page last free pid 5650 tgid 5650 ts 85122206691 stack trace:
 reset_page_owner include/linux/page_owner.h:26 [inline]
 __free_pages_prepare mm/page_alloc.c:1418 [inline]
 free_pages_prepare+0x9eb/0xaf0 mm/page_alloc.c:1463
 __free_contig_range_common+0x174/0x340 mm/page_alloc.c:7072
 __free_contig_range mm/page_alloc.c:7117 [inline]
 free_pages_bulk+0x48/0x120 mm/page_alloc.c:5322
 vm_area_free_pages mm/vmalloc.c:3461 [inline]
 vfree+0x231/0x490 mm/vmalloc.c:3510
 delayed_vfree_work+0x55/0x80 mm/vmalloc.c:3414
 process_one_work kernel/workqueue.c:3396 [inline]
 process_scheduled_works+0xc3d/0x1630 kernel/workqueue.c:3479
 worker_thread+0xa47/0xfb0 kernel/workqueue.c:3560
 kthread+0x38b/0x480 kernel/kthread.c:436
 ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

Memory state around the buggy address:
 ffff888035947000: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff888035947080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff888035947100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                                    ^
 ffff888035947180: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff888035947200: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================


---
This report is generated by a bot. It may contain errors.
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For information about bisection process see: https://goo.gl/tpsmEJ#bisection

If the report is already addressed, let syzbot know by replying with:
#syz fix: exact-commit-title

If you want syzbot to run the reproducer, reply with:
#syz test: git://repo/address.git branch-or-commit-hash
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Forwarded: [PATCH] wifi: ath9k: kill WMI event tasklet before freeing wmi

[syzbot]

For archival purposes, forwarding an incoming command email to
linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com.

***

Subject: [PATCH] wifi: ath9k: kill WMI event tasklet before freeing wmi
Author: kartikey406@gmail.com

#syz test: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master


The device becomes visible to the HTC/WMI RX path before
ath9k_htc_probe_device() has finished. If probe fails, the error path
stops WMI and kills the RX URBs, but ath9k_destroy_wmi() then frees
struct wmi while wmi_event_tasklet may still be scheduled from an event
that arrived earlier. tasklet_action_common() later walks the softirq
list and reads the freed tasklet, causing a slab-use-after-free.

Call tasklet_kill() and purge wmi_event_queue before kfree(). Callers
already set wmi->stopped and kill the RX URBs first, so the tasklet
cannot be re-armed after this point.

Reported-by: syzbot+e91dc13b1b37759b3d9f@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=e91dc13b1b37759b3d9f
Signed-off-by: Deepanshu Kartikey <kartikey406@gmail.com>
---
 drivers/net/wireless/ath/ath9k/wmi.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/net/wireless/ath/ath9k/wmi.c b/drivers/net/wireless/ath/ath9k/wmi.c
index 4a08babb6d9d..a629de91015b 100644
--- a/drivers/net/wireless/ath/ath9k/wmi.c
+++ b/drivers/net/wireless/ath/ath9k/wmi.c
@@ -122,6 +122,9 @@ void ath9k_stop_wmi(struct ath9k_htc_priv *priv)
 
 void ath9k_destroy_wmi(struct ath9k_htc_priv *priv)
 {
+	struct wmi *wmi = priv->wmi;
+	tasklet_kill(&wmi->wmi_event_tasklet);
+	skb_queue_purge(&wmi->wmi_event_queue);
 	kfree(priv->wmi);
 }
 
-- 
2.43.0

Forwarded: [PATCH] wifi: ath9k: stop WMI event tasklet from rescheduling itself on probe failure

[syzbot]

For archival purposes, forwarding an incoming command email to
linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com.

***

Subject: [PATCH] wifi: ath9k: stop WMI event tasklet from rescheduling itself on probe failure
Author: kartikey406@gmail.com

#syz test: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master


Since the init guards were consolidated, ath9k_wmi_event_tasklet()
reschedules itself until priv->initialized is set. If
ath9k_init_device() fails, initialized is never set, so the tasklet
keeps rescheduling itself while the probe error path calls
ath9k_destroy_wmi() and frees struct wmi. tasklet_action_common() then
touches the freed tasklet, causing a slab-use-after-free.

Make the tasklet drop its queued events and stop rescheduling once
wmi->stopped is set, and call tasklet_kill() before freeing wmi in
ath9k_destroy_wmi(). The probe error path already sets stopped and
kills the RX URBs first, so the tasklet cannot be re-armed afterwards.

Fixes: 1af8dc9ca726 ("wifi: ath9k: Clean up device initialisation guards")
Reported-by: syzbot+e91dc13b1b37759b3d9f@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=e91dc13b1b37759b3d9f
Signed-off-by: Deepanshu Kartikey <kartikey406@gmail.com>
---
 drivers/net/wireless/ath/ath9k/wmi.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/drivers/net/wireless/ath/ath9k/wmi.c b/drivers/net/wireless/ath/ath9k/wmi.c
index 4a08babb6d9d..f8b174b0f209 100644
--- a/drivers/net/wireless/ath/ath9k/wmi.c
+++ b/drivers/net/wireless/ath/ath9k/wmi.c
@@ -122,6 +122,9 @@ void ath9k_stop_wmi(struct ath9k_htc_priv *priv)
 
 void ath9k_destroy_wmi(struct ath9k_htc_priv *priv)
 {
+	struct wmi *wmi = priv->wmi;
+	tasklet_kill(&wmi->wmi_event_tasklet);
+	skb_queue_purge(&wmi->wmi_event_queue);
 	kfree(priv->wmi);
 }
 
@@ -148,6 +151,10 @@ void ath9k_wmi_event_tasklet(struct tasklet_struct *t)
 
 	/* Check if ath9k_init_device() completed. */
 	if (!smp_load_acquire(&priv->initialized)) {
+		if (READ_ONCE(wmi->stopped)) {
+			skb_queue_purge(&wmi->wmi_event_queue);
+			return;
+		}
 		tasklet_schedule(t);
 		return;
 	}
-- 
2.43.0