[v6.6] KASAN: slab-use-after-free Read in __io_req_complete_post
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syzbot
May 28, 2026, 11:47:27 PM (7 days ago) May 28
to syzkaller...@googlegroups.com
Hello,
syzbot found the following issue on:
HEAD commit: 0a40c6fbd105 Linux 6.6.141
git tree: linux-6.6.y
console output: https://syzkaller.appspot.com/x/log.txt?x=1631452e580000
kernel config: https://syzkaller.appspot.com/x/.config?x=90249d2d52c08134
dashboard link: https://syzkaller.appspot.com/bug?extid=9d5ba131e18eed0c503b
compiler: Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8
Unfortunately, I don't have any reproducer for this issue yet.
Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/f48d56604601/disk-0a40c6fb.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/cf126fb7ea87/vmlinux-0a40c6fb.xz
kernel image: https://storage.googleapis.com/syzbot-assets/8a5aa7959b43/bzImage-0a40c6fb.xz
IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+9d5ba1...@syzkaller.appspotmail.com
==================================================================
BUG: KASAN: slab-use-after-free in list_empty include/linux/list.h:373 [inline]
BUG: KASAN: slab-use-after-free in waitqueue_active include/linux/wait.h:129 [inline]
BUG: KASAN: slab-use-after-free in wq_has_sleeper include/linux/wait.h:163 [inline]
BUG: KASAN: slab-use-after-free in io_cqring_wake io_uring/io_uring.h:260 [inline]
BUG: KASAN: slab-use-after-free in io_cq_unlock_post io_uring/io_uring.c:647 [inline]
BUG: KASAN: slab-use-after-free in __io_req_complete_post+0x797/0x10a0 io_uring/io_uring.c:1012
Read of size 8 at addr ffff8880241322d8 by task kworker/1:0/23
CPU: 1 PID: 23 Comm: kworker/1:0 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/18/2026
Workqueue: events ublk_stop_work_fn
Call Trace:
<TASK>
dump_stack_lvl+0x18c/0x250 lib/dump_stack.c:106
print_address_description mm/kasan/report.c:364 [inline]
print_report+0xa8/0x210 mm/kasan/report.c:468
kasan_report+0x117/0x150 mm/kasan/report.c:581
list_empty include/linux/list.h:373 [inline]
waitqueue_active include/linux/wait.h:129 [inline]
wq_has_sleeper include/linux/wait.h:163 [inline]
io_cqring_wake io_uring/io_uring.h:260 [inline]
io_cq_unlock_post io_uring/io_uring.c:647 [inline]
__io_req_complete_post+0x797/0x10a0 io_uring/io_uring.c:1012
io_uring_cmd_done+0x247/0x370 io_uring/uring_cmd.c:72
ublk_cancel_queue drivers/block/ublk_drv.c:1564 [inline]
ublk_cancel_dev+0x1f5/0x3a0 drivers/block/ublk_drv.c:1577
ublk_stop_dev+0x36e/0x410 drivers/block/ublk_drv.c:1678
process_one_work kernel/workqueue.c:2653 [inline]
process_scheduled_works+0xa5d/0x15d0 kernel/workqueue.c:2730
worker_thread+0xa55/0xfc0 kernel/workqueue.c:2811
kthread+0x2fa/0x390 kernel/kthread.c:388
ret_from_fork+0x48/0x80 arch/x86/kernel/process.c:152
ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:293
</TASK>
Allocated by task 8080:
kasan_save_stack mm/kasan/common.c:46 [inline]
kasan_set_track+0x4e/0x70 mm/kasan/common.c:53
____kasan_kmalloc mm/kasan/common.c:375 [inline]
__kasan_kmalloc+0x8f/0xa0 mm/kasan/common.c:384
kmalloc include/linux/slab.h:600 [inline]
kzalloc include/linux/slab.h:721 [inline]
io_ring_ctx_alloc+0x54/0xc10 io_uring/io_uring.c:289
io_uring_create+0x2de/0x1320 io_uring/io_uring.c:3993
io_uring_setup io_uring/io_uring.c:4178 [inline]
__do_sys_io_uring_setup io_uring/io_uring.c:4205 [inline]
__se_sys_io_uring_setup+0x29f/0x2b0 io_uring/io_uring.c:4199
do_syscall_x64 arch/x86/entry/common.c:46 [inline]
do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:76
entry_SYSCALL_64_after_hwframe+0x68/0xd2
Freed by task 6348:
kasan_save_stack mm/kasan/common.c:46 [inline]
kasan_set_track+0x4e/0x70 mm/kasan/common.c:53
kasan_save_free_info+0x2e/0x50 mm/kasan/generic.c:522
____kasan_slab_free+0x126/0x1e0 mm/kasan/common.c:237
kasan_slab_free include/linux/kasan.h:164 [inline]
slab_free_hook mm/slub.c:1811 [inline]
slab_free_freelist_hook+0x130/0x1a0 mm/slub.c:1837
slab_free mm/slub.c:3830 [inline]
__kmem_cache_free+0xba/0x1e0 mm/slub.c:3843
io_ring_exit_work+0x795/0x820 io_uring/io_uring.c:3264
process_one_work kernel/workqueue.c:2653 [inline]
process_scheduled_works+0xa5d/0x15d0 kernel/workqueue.c:2730
worker_thread+0xa55/0xfc0 kernel/workqueue.c:2811
kthread+0x2fa/0x390 kernel/kthread.c:388
ret_from_fork+0x48/0x80 arch/x86/kernel/process.c:152
ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:293
Last potentially related work creation:
kasan_save_stack+0x3e/0x60 mm/kasan/common.c:46
__kasan_record_aux_stack+0xaf/0xc0 mm/kasan/generic.c:492
insert_work+0x3d/0x310 kernel/workqueue.c:1670
__queue_work+0xc39/0x1020 kernel/workqueue.c:1819
queue_work_on+0x128/0x1f0 kernel/workqueue.c:1854
queue_work include/linux/workqueue.h:562 [inline]
io_ring_ctx_wait_and_kill+0x256/0x2b0 io_uring/io_uring.c:3296
io_uring_release+0x42/0x50 io_uring/io_uring.c:3304
__fput+0x234/0x970 fs/file_table.c:384
task_work_run+0x1d4/0x260 kernel/task_work.c:245
exit_task_work include/linux/task_work.h:43 [inline]
do_exit+0x95a/0x2460 kernel/exit.c:884
do_group_exit+0x21b/0x2d0 kernel/exit.c:1026
get_signal+0x12fc/0x13f0 kernel/signal.c:2902
arch_do_signal_or_restart+0xc2/0x800 arch/x86/kernel/signal.c:310
exit_to_user_mode_loop+0x70/0x110 kernel/entry/common.c:174
exit_to_user_mode_prepare+0xee/0x180 kernel/entry/common.c:210
__syscall_exit_to_user_mode_work kernel/entry/common.c:291 [inline]
syscall_exit_to_user_mode+0x1a/0x50 kernel/entry/common.c:302
do_syscall_64+0x61/0xb0 arch/x86/entry/common.c:82
entry_SYSCALL_64_after_hwframe+0x68/0xd2
The buggy address belongs to the object at ffff888024132000
which belongs to the cache kmalloc-4k of size 4096
The buggy address is located 728 bytes inside of
freed 4096-byte region [ffff888024132000, ffff888024133000)
The buggy address belongs to the physical page:
page:ffffea0000904c00 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x24130
head:ffffea0000904c00 order:3 entire_mapcount:0 nr_pages_mapped:0 pincount:0
anon flags: 0xfff00000000840(slab|head|node=0|zone=1|lastcpupid=0x7ff)
page_type: 0xffffffff()
raw: 00fff00000000840 ffff888017c42140 0000000000000000 dead000000000001
raw: 0000000000000000 0000000000040004 00000001ffffffff 0000000000000000
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 1, tgid 1 (swapper/0), ts 9583704758, free_ts 0
set_page_owner include/linux/page_owner.h:31 [inline]
post_alloc_hook+0x1c1/0x200 mm/page_alloc.c:1581
prep_new_page mm/page_alloc.c:1588 [inline]
get_page_from_freelist+0x1951/0x19e0 mm/page_alloc.c:3220
__alloc_pages+0x1f0/0x460 mm/page_alloc.c:4500
alloc_page_interleave+0x24/0x1e0 mm/mempolicy.c:2118
alloc_slab_page+0x5d/0x160 mm/slub.c:1881
allocate_slab mm/slub.c:2028 [inline]
new_slab+0x87/0x2d0 mm/slub.c:2081
___slab_alloc+0xc5d/0x12f0 mm/slub.c:3253
__slab_alloc mm/slub.c:3339 [inline]
__slab_alloc_node mm/slub.c:3392 [inline]
slab_alloc_node mm/slub.c:3485 [inline]
__kmem_cache_alloc_node+0x19e/0x250 mm/slub.c:3534
kmalloc_trace+0x2a/0xe0 mm/slab_common.c:1098
kmalloc include/linux/slab.h:600 [inline]
kzalloc include/linux/slab.h:721 [inline]
kobject_uevent_env+0x274/0x8b0 lib/kobject_uevent.c:539
driver_register+0x2d4/0x310 drivers/base/driver.c:254
usb_register_driver+0x206/0x3d0 drivers/usb/core/driver.c:1062
ath9k_htc_init+0x10/0x50 drivers/net/wireless/ath/ath9k/htc_drv_init.c:1027
do_one_initcall+0x242/0x790 init/main.c:1249
do_initcall_level+0x137/0x1f0 init/main.c:1311
do_initcalls+0x69/0xd0 init/main.c:1327
page_owner free stack trace missing
Memory state around the buggy address:
ffff888024132180: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff888024132200: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff888024132280: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff888024132300: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff888024132380: 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.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzk...@googlegroups.com.
syzbot will keep track of this issue. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
If the report is already addressed, let syzbot know by replying with:
#syz fix: exact-commit-title
If you want to overwrite report's subsystems, reply with:
#syz set subsystems: new-subsystem
(See the list of subsystem names on the web dashboard)
If the report is a duplicate of another one, reply with:
#syz dup: exact-subject-of-another-report
If you want to undo deduplication, reply with:
#syz undup
syzbot found the following issue on:
HEAD commit: 0a40c6fbd105 Linux 6.6.141
git tree: linux-6.6.y
console output: https://syzkaller.appspot.com/x/log.txt?x=1631452e580000
kernel config: https://syzkaller.appspot.com/x/.config?x=90249d2d52c08134
dashboard link: https://syzkaller.appspot.com/bug?extid=9d5ba131e18eed0c503b
compiler: Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8
Unfortunately, I don't have any reproducer for this issue yet.
Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/f48d56604601/disk-0a40c6fb.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/cf126fb7ea87/vmlinux-0a40c6fb.xz
kernel image: https://storage.googleapis.com/syzbot-assets/8a5aa7959b43/bzImage-0a40c6fb.xz
IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+9d5ba1...@syzkaller.appspotmail.com
==================================================================
BUG: KASAN: slab-use-after-free in list_empty include/linux/list.h:373 [inline]
BUG: KASAN: slab-use-after-free in waitqueue_active include/linux/wait.h:129 [inline]
BUG: KASAN: slab-use-after-free in wq_has_sleeper include/linux/wait.h:163 [inline]
BUG: KASAN: slab-use-after-free in io_cqring_wake io_uring/io_uring.h:260 [inline]
BUG: KASAN: slab-use-after-free in io_cq_unlock_post io_uring/io_uring.c:647 [inline]
BUG: KASAN: slab-use-after-free in __io_req_complete_post+0x797/0x10a0 io_uring/io_uring.c:1012
Read of size 8 at addr ffff8880241322d8 by task kworker/1:0/23
CPU: 1 PID: 23 Comm: kworker/1:0 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/18/2026
Workqueue: events ublk_stop_work_fn
Call Trace:
<TASK>
dump_stack_lvl+0x18c/0x250 lib/dump_stack.c:106
print_address_description mm/kasan/report.c:364 [inline]
print_report+0xa8/0x210 mm/kasan/report.c:468
kasan_report+0x117/0x150 mm/kasan/report.c:581
list_empty include/linux/list.h:373 [inline]
waitqueue_active include/linux/wait.h:129 [inline]
wq_has_sleeper include/linux/wait.h:163 [inline]
io_cqring_wake io_uring/io_uring.h:260 [inline]
io_cq_unlock_post io_uring/io_uring.c:647 [inline]
__io_req_complete_post+0x797/0x10a0 io_uring/io_uring.c:1012
io_uring_cmd_done+0x247/0x370 io_uring/uring_cmd.c:72
ublk_cancel_queue drivers/block/ublk_drv.c:1564 [inline]
ublk_cancel_dev+0x1f5/0x3a0 drivers/block/ublk_drv.c:1577
ublk_stop_dev+0x36e/0x410 drivers/block/ublk_drv.c:1678
process_one_work kernel/workqueue.c:2653 [inline]
process_scheduled_works+0xa5d/0x15d0 kernel/workqueue.c:2730
worker_thread+0xa55/0xfc0 kernel/workqueue.c:2811
kthread+0x2fa/0x390 kernel/kthread.c:388
ret_from_fork+0x48/0x80 arch/x86/kernel/process.c:152
ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:293
</TASK>
Allocated by task 8080:
kasan_save_stack mm/kasan/common.c:46 [inline]
kasan_set_track+0x4e/0x70 mm/kasan/common.c:53
____kasan_kmalloc mm/kasan/common.c:375 [inline]
__kasan_kmalloc+0x8f/0xa0 mm/kasan/common.c:384
kmalloc include/linux/slab.h:600 [inline]
kzalloc include/linux/slab.h:721 [inline]
io_ring_ctx_alloc+0x54/0xc10 io_uring/io_uring.c:289
io_uring_create+0x2de/0x1320 io_uring/io_uring.c:3993
io_uring_setup io_uring/io_uring.c:4178 [inline]
__do_sys_io_uring_setup io_uring/io_uring.c:4205 [inline]
__se_sys_io_uring_setup+0x29f/0x2b0 io_uring/io_uring.c:4199
do_syscall_x64 arch/x86/entry/common.c:46 [inline]
do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:76
entry_SYSCALL_64_after_hwframe+0x68/0xd2
Freed by task 6348:
kasan_save_stack mm/kasan/common.c:46 [inline]
kasan_set_track+0x4e/0x70 mm/kasan/common.c:53
kasan_save_free_info+0x2e/0x50 mm/kasan/generic.c:522
____kasan_slab_free+0x126/0x1e0 mm/kasan/common.c:237
kasan_slab_free include/linux/kasan.h:164 [inline]
slab_free_hook mm/slub.c:1811 [inline]
slab_free_freelist_hook+0x130/0x1a0 mm/slub.c:1837
slab_free mm/slub.c:3830 [inline]
__kmem_cache_free+0xba/0x1e0 mm/slub.c:3843
io_ring_exit_work+0x795/0x820 io_uring/io_uring.c:3264
process_one_work kernel/workqueue.c:2653 [inline]
process_scheduled_works+0xa5d/0x15d0 kernel/workqueue.c:2730
worker_thread+0xa55/0xfc0 kernel/workqueue.c:2811
kthread+0x2fa/0x390 kernel/kthread.c:388
ret_from_fork+0x48/0x80 arch/x86/kernel/process.c:152
ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:293
Last potentially related work creation:
kasan_save_stack+0x3e/0x60 mm/kasan/common.c:46
__kasan_record_aux_stack+0xaf/0xc0 mm/kasan/generic.c:492
insert_work+0x3d/0x310 kernel/workqueue.c:1670
__queue_work+0xc39/0x1020 kernel/workqueue.c:1819
queue_work_on+0x128/0x1f0 kernel/workqueue.c:1854
queue_work include/linux/workqueue.h:562 [inline]
io_ring_ctx_wait_and_kill+0x256/0x2b0 io_uring/io_uring.c:3296
io_uring_release+0x42/0x50 io_uring/io_uring.c:3304
__fput+0x234/0x970 fs/file_table.c:384
task_work_run+0x1d4/0x260 kernel/task_work.c:245
exit_task_work include/linux/task_work.h:43 [inline]
do_exit+0x95a/0x2460 kernel/exit.c:884
do_group_exit+0x21b/0x2d0 kernel/exit.c:1026
get_signal+0x12fc/0x13f0 kernel/signal.c:2902
arch_do_signal_or_restart+0xc2/0x800 arch/x86/kernel/signal.c:310
exit_to_user_mode_loop+0x70/0x110 kernel/entry/common.c:174
exit_to_user_mode_prepare+0xee/0x180 kernel/entry/common.c:210
__syscall_exit_to_user_mode_work kernel/entry/common.c:291 [inline]
syscall_exit_to_user_mode+0x1a/0x50 kernel/entry/common.c:302
do_syscall_64+0x61/0xb0 arch/x86/entry/common.c:82
entry_SYSCALL_64_after_hwframe+0x68/0xd2
The buggy address belongs to the object at ffff888024132000
which belongs to the cache kmalloc-4k of size 4096
The buggy address is located 728 bytes inside of
freed 4096-byte region [ffff888024132000, ffff888024133000)
The buggy address belongs to the physical page:
page:ffffea0000904c00 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x24130
head:ffffea0000904c00 order:3 entire_mapcount:0 nr_pages_mapped:0 pincount:0
anon flags: 0xfff00000000840(slab|head|node=0|zone=1|lastcpupid=0x7ff)
page_type: 0xffffffff()
raw: 00fff00000000840 ffff888017c42140 0000000000000000 dead000000000001
raw: 0000000000000000 0000000000040004 00000001ffffffff 0000000000000000
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 1, tgid 1 (swapper/0), ts 9583704758, free_ts 0
set_page_owner include/linux/page_owner.h:31 [inline]
post_alloc_hook+0x1c1/0x200 mm/page_alloc.c:1581
prep_new_page mm/page_alloc.c:1588 [inline]
get_page_from_freelist+0x1951/0x19e0 mm/page_alloc.c:3220
__alloc_pages+0x1f0/0x460 mm/page_alloc.c:4500
alloc_page_interleave+0x24/0x1e0 mm/mempolicy.c:2118
alloc_slab_page+0x5d/0x160 mm/slub.c:1881
allocate_slab mm/slub.c:2028 [inline]
new_slab+0x87/0x2d0 mm/slub.c:2081
___slab_alloc+0xc5d/0x12f0 mm/slub.c:3253
__slab_alloc mm/slub.c:3339 [inline]
__slab_alloc_node mm/slub.c:3392 [inline]
slab_alloc_node mm/slub.c:3485 [inline]
__kmem_cache_alloc_node+0x19e/0x250 mm/slub.c:3534
kmalloc_trace+0x2a/0xe0 mm/slab_common.c:1098
kmalloc include/linux/slab.h:600 [inline]
kzalloc include/linux/slab.h:721 [inline]
kobject_uevent_env+0x274/0x8b0 lib/kobject_uevent.c:539
driver_register+0x2d4/0x310 drivers/base/driver.c:254
usb_register_driver+0x206/0x3d0 drivers/usb/core/driver.c:1062
ath9k_htc_init+0x10/0x50 drivers/net/wireless/ath/ath9k/htc_drv_init.c:1027
do_one_initcall+0x242/0x790 init/main.c:1249
do_initcall_level+0x137/0x1f0 init/main.c:1311
do_initcalls+0x69/0xd0 init/main.c:1327
page_owner free stack trace missing
Memory state around the buggy address:
ffff888024132180: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff888024132200: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff888024132280: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff888024132300: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff888024132380: 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.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzk...@googlegroups.com.
syzbot will keep track of this issue. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
If the report is already addressed, let syzbot know by replying with:
#syz fix: exact-commit-title
If you want to overwrite report's subsystems, reply with:
#syz set subsystems: new-subsystem
(See the list of subsystem names on the web dashboard)
If the report is a duplicate of another one, reply with:
#syz dup: exact-subject-of-another-report
If you want to undo deduplication, reply with:
#syz undup
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