Re: [syzbot] KASAN: use-after-free Write in io_queue_worker_create

syzbot
2021-12-10T05:21:18Z

syzbot has found a reproducer for the following issue on:

HEAD commit: c741e49150db Merge tag 'for-linus' of git://git.kernel.org..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=125600bab00000
kernel config: https://syzkaller.appspot.com/x/.config?x=221ffc09e39ebbd1
dashboard link: https://syzkaller.appspot.com/bug?extid=b60c982cb0efc5e05a47
compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=1686906db00000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=1539a9b9b00000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+b60c982cb0efc5e05a47@syzkaller.appspotmail.com

==================================================================
BUG: KASAN: use-after-free in instrument_atomic_write include/linux/instrumented.h:86 [inline]
BUG: KASAN: use-after-free in clear_bit_unlock include/asm-generic/bitops/instrumented-lock.h:25 [inline]
BUG: KASAN: use-after-free in io_queue_worker_create+0x453/0x4e0 fs/io-wq.c:363
Write of size 8 at addr ffff88806e6920d8 by task kworker/1:1/25

CPU: 1 PID: 25 Comm: kworker/1:1 Not tainted 5.16.0-rc4-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Workqueue: events io_workqueue_create
Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:88 [inline]
dump_stack_lvl+0xcd/0x134 lib/dump_stack.c:106
print_address_description.constprop.0.cold+0x8d/0x320 mm/kasan/report.c:247
__kasan_report mm/kasan/report.c:433 [inline]
kasan_report.cold+0x83/0xdf mm/kasan/report.c:450
check_region_inline mm/kasan/generic.c:183 [inline]
kasan_check_range+0x13d/0x180 mm/kasan/generic.c:189
instrument_atomic_write include/linux/instrumented.h:86 [inline]
clear_bit_unlock include/asm-generic/bitops/instrumented-lock.h:25 [inline]
io_queue_worker_create+0x453/0x4e0 fs/io-wq.c:363
io_workqueue_create+0x9e/0xe0 fs/io-wq.c:780
process_one_work+0x9b2/0x1690 kernel/workqueue.c:2298
worker_thread+0x658/0x11f0 kernel/workqueue.c:2445
kthread+0x405/0x4f0 kernel/kthread.c:327
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295
</TASK>

Allocated by task 4385:
kasan_save_stack+0x1e/0x50 mm/kasan/common.c:38
kasan_set_track mm/kasan/common.c:46 [inline]
set_alloc_info mm/kasan/common.c:434 [inline]
____kasan_kmalloc mm/kasan/common.c:513 [inline]
____kasan_kmalloc mm/kasan/common.c:472 [inline]
__kasan_kmalloc+0xa9/0xd0 mm/kasan/common.c:522
kmalloc_node include/linux/slab.h:608 [inline]
kzalloc_node include/linux/slab.h:735 [inline]
create_io_worker+0x108/0x630 fs/io-wq.c:792
create_worker_cb+0x202/0x270 fs/io-wq.c:329
task_work_run+0xdd/0x1a0 kernel/task_work.c:164
tracehook_notify_signal include/linux/tracehook.h:214 [inline]
handle_signal_work kernel/entry/common.c:146 [inline]
exit_to_user_mode_loop kernel/entry/common.c:172 [inline]
exit_to_user_mode_prepare+0x256/0x290 kernel/entry/common.c:207
__syscall_exit_to_user_mode_work kernel/entry/common.c:289 [inline]
syscall_exit_to_user_mode+0x19/0x60 kernel/entry/common.c:300
do_syscall_64+0x42/0xb0 arch/x86/entry/common.c:86
entry_SYSCALL_64_after_hwframe+0x44/0xae

Freed by task 4385:
kasan_save_stack+0x1e/0x50 mm/kasan/common.c:38
kasan_set_track+0x21/0x30 mm/kasan/common.c:46
kasan_set_free_info+0x20/0x30 mm/kasan/generic.c:370
____kasan_slab_free mm/kasan/common.c:366 [inline]
____kasan_slab_free mm/kasan/common.c:328 [inline]
__kasan_slab_free+0xff/0x130 mm/kasan/common.c:374
kasan_slab_free include/linux/kasan.h:235 [inline]
slab_free_hook mm/slub.c:1723 [inline]
slab_free_freelist_hook+0x8b/0x1c0 mm/slub.c:1749
slab_free mm/slub.c:3513 [inline]
kfree+0xf6/0x560 mm/slub.c:4561
create_worker_cont+0x3fb/0x550 fs/io-wq.c:766
task_work_run+0xdd/0x1a0 kernel/task_work.c:164
tracehook_notify_signal include/linux/tracehook.h:214 [inline]
handle_signal_work kernel/entry/common.c:146 [inline]
exit_to_user_mode_loop kernel/entry/common.c:172 [inline]
exit_to_user_mode_prepare+0x256/0x290 kernel/entry/common.c:207
__syscall_exit_to_user_mode_work kernel/entry/common.c:289 [inline]
syscall_exit_to_user_mode+0x19/0x60 kernel/entry/common.c:300
do_syscall_64+0x42/0xb0 arch/x86/entry/common.c:86
entry_SYSCALL_64_after_hwframe+0x44/0xae

Last potentially related work creation:
kasan_save_stack+0x1e/0x50 mm/kasan/common.c:38
__kasan_record_aux_stack+0xf5/0x120 mm/kasan/generic.c:348
task_work_add+0x3a/0x190 kernel/task_work.c:38
io_queue_worker_create+0x3ee/0x4e0 fs/io-wq.c:362
io_workqueue_create+0x9e/0xe0 fs/io-wq.c:780
process_one_work+0x9b2/0x1690 kernel/workqueue.c:2298
worker_thread+0x658/0x11f0 kernel/workqueue.c:2445
kthread+0x405/0x4f0 kernel/kthread.c:327
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295

Second to last potentially related work creation:
kasan_save_stack+0x1e/0x50 mm/kasan/common.c:38
__kasan_record_aux_stack+0xf5/0x120 mm/kasan/generic.c:348
insert_work+0x48/0x370 kernel/workqueue.c:1354
__queue_work+0x5ca/0xee0 kernel/workqueue.c:1520
queue_work_on+0xee/0x110 kernel/workqueue.c:1547
queue_work include/linux/workqueue.h:502 [inline]
schedule_work include/linux/workqueue.h:563 [inline]
create_worker_cont+0x44b/0x550 fs/io-wq.c:772
task_work_run+0xdd/0x1a0 kernel/task_work.c:164
tracehook_notify_signal include/linux/tracehook.h:214 [inline]
handle_signal_work kernel/entry/common.c:146 [inline]
exit_to_user_mode_loop kernel/entry/common.c:172 [inline]
exit_to_user_mode_prepare+0x256/0x290 kernel/entry/common.c:207
__syscall_exit_to_user_mode_work kernel/entry/common.c:289 [inline]
syscall_exit_to_user_mode+0x19/0x60 kernel/entry/common.c:300
do_syscall_64+0x42/0xb0 arch/x86/entry/common.c:86
entry_SYSCALL_64_after_hwframe+0x44/0xae

The buggy address belongs to the object at ffff88806e692000
which belongs to the cache kmalloc-512 of size 512
The buggy address is located 216 bytes inside of
512-byte region [ffff88806e692000, ffff88806e692200)
The buggy address belongs to the page:
page:ffffea0001b9a400 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x6e690
head:ffffea0001b9a400 order:2 compound_mapcount:0 compound_pincount:0
flags: 0xfff00000010200(slab|head|node=0|zone=1|lastcpupid=0x7ff)
raw: 00fff00000010200 0000000000000000 dead000000000122 ffff888010c41c80
raw: 0000000000000000 0000000000100010 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 2, migratetype Unmovable, gfp_mask 0x1d20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC|__GFP_HARDWALL), pid 4385, ts 49566988561, free_ts 10514971018
prep_new_page mm/page_alloc.c:2418 [inline]
get_page_from_freelist+0xa72/0x2f50 mm/page_alloc.c:4149
__alloc_pages+0x1b2/0x500 mm/page_alloc.c:5369
__alloc_pages_node include/linux/gfp.h:570 [inline]
alloc_slab_page mm/slub.c:1795 [inline]
allocate_slab mm/slub.c:1930 [inline]
new_slab+0xab/0x4a0 mm/slub.c:1993
___slab_alloc+0x918/0xfe0 mm/slub.c:3022
__slab_alloc.constprop.0+0x4d/0xa0 mm/slub.c:3109
slab_alloc_node mm/slub.c:3200 [inline]
kmem_cache_alloc_node_trace+0x116/0x310 mm/slub.c:3284
kmalloc_node include/linux/slab.h:608 [inline]
kzalloc_node include/linux/slab.h:735 [inline]
create_io_worker+0x108/0x630 fs/io-wq.c:792
create_worker_cb+0x202/0x270 fs/io-wq.c:329
task_work_run+0xdd/0x1a0 kernel/task_work.c:164
tracehook_notify_signal include/linux/tracehook.h:214 [inline]
handle_signal_work kernel/entry/common.c:146 [inline]
exit_to_user_mode_loop kernel/entry/common.c:172 [inline]
exit_to_user_mode_prepare+0x256/0x290 kernel/entry/common.c:207
__syscall_exit_to_user_mode_work kernel/entry/common.c:289 [inline]
syscall_exit_to_user_mode+0x19/0x60 kernel/entry/common.c:300
do_syscall_64+0x42/0xb0 arch/x86/entry/common.c:86
entry_SYSCALL_64_after_hwframe+0x44/0xae
page last free stack trace:
reset_page_owner include/linux/page_owner.h:24 [inline]
free_pages_prepare mm/page_alloc.c:1338 [inline]
free_pcp_prepare+0x374/0x870 mm/page_alloc.c:1389
free_unref_page_prepare mm/page_alloc.c:3309 [inline]
free_unref_page+0x19/0x690 mm/page_alloc.c:3388
free_contig_range+0xa8/0xf0 mm/page_alloc.c:9271
destroy_args+0xa8/0x646 mm/debug_vm_pgtable.c:1016
debug_vm_pgtable+0x2984/0x2a16 mm/debug_vm_pgtable.c:1330
do_one_initcall+0x103/0x650 init/main.c:1297
do_initcall_level init/main.c:1370 [inline]
do_initcalls init/main.c:1386 [inline]
do_basic_setup init/main.c:1405 [inline]
kernel_init_freeable+0x6b1/0x73a init/main.c:1610
kernel_init+0x1a/0x1d0 init/main.c:1499
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295

Memory state around the buggy address:
ffff88806e691f80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff88806e692000: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff88806e692080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff88806e692100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff88806e692180: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================