[syzbot] KASAN: use-after-free Read in io_poll_check_events

syzbot
2022-02-19T09:20:27Z

Hello,

syzbot found the following issue on:

HEAD commit: d567f5db412e Merge tag 'regulator-fix-v5.17-rc4' of git://..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=137545a4700000
kernel config: https://syzkaller.appspot.com/x/.config?x=c252f01504189189
dashboard link: https://syzkaller.appspot.com/bug?extid=edb9c7738ba8cbdbf197
compiler: Debian clang version 11.0.1-2, GNU ld (GNU Binutils for Debian) 2.35.2

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

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+edb9c7738ba8cbdbf197@syzkaller.appspotmail.com

==================================================================
BUG: KASAN: use-after-free in io_poll_check_events+0x994/0x9a0 fs/io_uring.c:5516
Read of size 4 at addr ffff88802452ba2c by task kworker/1:21/2630

CPU: 1 PID: 2630 Comm: kworker/1:21 Not tainted 5.17.0-rc4-syzkaller-00002-gd567f5db412e #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Workqueue: events io_fallback_req_func
Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:88 [inline]
dump_stack_lvl+0x1dc/0x2d8 lib/dump_stack.c:106
print_address_description+0x65/0x3a0 mm/kasan/report.c:255
__kasan_report mm/kasan/report.c:442 [inline]
kasan_report+0x19a/0x1f0 mm/kasan/report.c:459
io_poll_check_events+0x994/0x9a0 fs/io_uring.c:5516
io_apoll_task_func+0x4c/0xb10 fs/io_uring.c:5590
io_fallback_req_func+0x118/0x1fd fs/io_uring.c:1400
process_one_work+0x86c/0x1190 kernel/workqueue.c:2307
worker_thread+0xab1/0x1300 kernel/workqueue.c:2454
kthread+0x2a3/0x2d0 kernel/kthread.c:377
ret_from_fork+0x1f/0x30
</TASK>

Allocated by task 9351:
kasan_save_stack mm/kasan/common.c:38 [inline]
kasan_set_track mm/kasan/common.c:45 [inline]
set_alloc_info mm/kasan/common.c:436 [inline]
__kasan_slab_alloc+0xb2/0xe0 mm/kasan/common.c:469
kasan_slab_alloc include/linux/kasan.h:260 [inline]
slab_post_alloc_hook mm/slab.h:732 [inline]
slab_alloc_node mm/slub.c:3230 [inline]
kmem_cache_alloc_node+0x201/0x370 mm/slub.c:3266
alloc_task_struct_node kernel/fork.c:171 [inline]
dup_task_struct+0x52/0x9a0 kernel/fork.c:883
copy_process+0x64a/0x5aa0 kernel/fork.c:1998
kernel_clone+0x22a/0x7e0 kernel/fork.c:2555
__do_sys_clone kernel/fork.c:2672 [inline]
__se_sys_clone kernel/fork.c:2656 [inline]
__x64_sys_clone+0x245/0x2b0 kernel/fork.c:2656
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x44/0xd0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x44/0xae

Freed by task 2630:
kasan_save_stack mm/kasan/common.c:38 [inline]
kasan_set_track+0x4c/0x70 mm/kasan/common.c:45
kasan_set_free_info+0x1f/0x40 mm/kasan/generic.c:370
____kasan_slab_free+0x126/0x180 mm/kasan/common.c:366
kasan_slab_free include/linux/kasan.h:236 [inline]
slab_free_hook mm/slub.c:1728 [inline]
slab_free_freelist_hook+0x12e/0x1a0 mm/slub.c:1754
slab_free mm/slub.c:3509 [inline]
kmem_cache_free+0xb6/0x1c0 mm/slub.c:3526
__io_req_complete_post+0x25c/0x470 fs/io_uring.c:1960
io_req_complete_post fs/io_uring.c:1972 [inline]
io_req_complete_failed fs/io_uring.c:2003 [inline]
io_apoll_task_func+0x226/0xb10 fs/io_uring.c:5602
io_fallback_req_func+0x118/0x1fd fs/io_uring.c:1400
process_one_work+0x86c/0x1190 kernel/workqueue.c:2307
worker_thread+0xab1/0x1300 kernel/workqueue.c:2454
kthread+0x2a3/0x2d0 kernel/kthread.c:377
ret_from_fork+0x1f/0x30

Last potentially related work creation:
kasan_save_stack+0x3b/0x60 mm/kasan/common.c:38
__kasan_record_aux_stack+0xb2/0xc0 mm/kasan/generic.c:348
__call_rcu kernel/rcu/tree.c:3026 [inline]
call_rcu+0x1c4/0xa70 kernel/rcu/tree.c:3106
context_switch kernel/sched/core.c:4990 [inline]
__schedule+0x92e/0x1080 kernel/sched/core.c:6296
preempt_schedule_common kernel/sched/core.c:6462 [inline]
preempt_schedule+0x14d/0x190 kernel/sched/core.c:6487
preempt_schedule_thunk+0x16/0x18
__raw_spin_unlock_irq include/linux/spinlock_api_smp.h:160 [inline]
_raw_spin_unlock_irq+0x3c/0x40 kernel/locking/spinlock.c:202
spin_unlock_irq include/linux/spinlock.h:399 [inline]
do_group_exit+0x29f/0x2b0 kernel/exit.c:932
__do_sys_exit_group+0x13/0x20 kernel/exit.c:946
__ia32_sys_exit_group+0x0/0x40 kernel/exit.c:944
__x64_sys_exit_group+0x37/0x40 kernel/exit.c:944
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x44/0xd0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x44/0xae

Second to last potentially related work creation:
kasan_save_stack+0x3b/0x60 mm/kasan/common.c:38
__kasan_record_aux_stack+0xb2/0xc0 mm/kasan/generic.c:348
__call_rcu kernel/rcu/tree.c:3026 [inline]
call_rcu+0x1c4/0xa70 kernel/rcu/tree.c:3106
put_task_struct_rcu_user kernel/exit.c:180 [inline]
release_task+0x133b/0x15d0 kernel/exit.c:226
wait_task_zombie kernel/exit.c:1121 [inline]
wait_consider_task+0x1995/0x3020 kernel/exit.c:1348
do_wait_thread kernel/exit.c:1411 [inline]
do_wait+0x291/0x9d0 kernel/exit.c:1528
kernel_wait4+0x2a3/0x3c0 kernel/exit.c:1691
__do_sys_wait4 kernel/exit.c:1719 [inline]
__se_sys_wait4 kernel/exit.c:1715 [inline]
__x64_sys_wait4+0x130/0x1e0 kernel/exit.c:1715
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x44/0xd0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x44/0xae

The buggy address belongs to the object at ffff88802452ba00
which belongs to the cache task_struct of size 7168
The buggy address is located 44 bytes inside of
7168-byte region [ffff88802452ba00, ffff88802452d600)
The buggy address belongs to the page:
page:ffffea0000914a00 refcount:1 mapcount:0 mapping:0000000000000000 index:0xffff888024528000 pfn:0x24528
head:ffffea0000914a00 order:3 compound_mapcount:0 compound_pincount:0
memcg:ffff88801b05ff01
flags: 0xfff00000010200(slab|head|node=0|zone=1|lastcpupid=0x7ff)
raw: 00fff00000010200 ffffea00008c1408 ffffea0001f56408 ffff888140006280
raw: ffff888024528000 0000000000040002 00000001ffffffff ffff88801b05ff01
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 2, ts 12556673292, free_ts 0
prep_new_page mm/page_alloc.c:2434 [inline]
get_page_from_freelist+0x729/0x9e0 mm/page_alloc.c:4165
__alloc_pages+0x255/0x580 mm/page_alloc.c:5389
alloc_slab_page mm/slub.c:1799 [inline]
allocate_slab+0xce/0x3f0 mm/slub.c:1944
new_slab mm/slub.c:2004 [inline]
___slab_alloc+0x3fe/0xc30 mm/slub.c:3018
__slab_alloc mm/slub.c:3105 [inline]
slab_alloc_node mm/slub.c:3196 [inline]
kmem_cache_alloc_node+0x2bb/0x370 mm/slub.c:3266
alloc_task_struct_node kernel/fork.c:171 [inline]
dup_task_struct+0x52/0x9a0 kernel/fork.c:883
copy_process+0x64a/0x5aa0 kernel/fork.c:1998
kernel_clone+0x22a/0x7e0 kernel/fork.c:2555
kernel_thread+0x155/0x1d0 kernel/fork.c:2607
create_kthread kernel/kthread.c:400 [inline]
kthreadd+0x5b5/0x7a0 kernel/kthread.c:746
ret_from_fork+0x1f/0x30
page_owner free stack trace missing

Memory state around the buggy address:
ffff88802452b900: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff88802452b980: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff88802452ba00: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff88802452ba80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff88802452bb00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================

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