KASAN: use-after-free Read in io_async_task

KASAN: use-after-free Read in io_async_task_func
Status: fixed on 2020/09/16 22:51
Reported-by: syzbot+9b260fc33297966f5a8e@syzkaller.appspotmail.com
Fix commit: 6d816e08 io_uring: hold 'ctx' reference around task_work queue + execute
First crash: 42d, last: 42d

Cause bisection: failed (bisect log)

duplicates (2):
Title	Repro	Bisected	Count	Last	Reported	Patched	Status
KASAN: use-after-free Read in idr_for_each	C		4	21d	39d	0/17	closed as dup on 2020/08/13 18:43
KASAN: use-after-free Read in __io_req_task_submit	C	cause	1	41d	41d	0/17	closed as dup on 2020/08/12 02:44

Sample crash report:

==================================================================
BUG: KASAN: use-after-free in instrument_atomic_read include/linux/instrumented.h:56 [inline]
BUG: KASAN: use-after-free in atomic64_read include/asm-generic/atomic-instrumented.h:837 [inline]
BUG: KASAN: use-after-free in atomic_long_read include/asm-generic/atomic-long.h:29 [inline]
BUG: KASAN: use-after-free in __mutex_unlock_slowpath+0x88/0x590 kernel/locking/mutex.c:1237
Read of size 8 at addr ffff8880952503c0 by task syz-executor.1/23201

CPU: 0 PID: 23201 Comm: syz-executor.1 Not tainted 5.8.0-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0x1f0/0x31e lib/dump_stack.c:118
 print_address_description+0x66/0x620 mm/kasan/report.c:383
 __kasan_report mm/kasan/report.c:513 [inline]
 kasan_report+0x132/0x1d0 mm/kasan/report.c:530
 check_memory_region_inline mm/kasan/generic.c:183 [inline]
 check_memory_region+0x2b5/0x2f0 mm/kasan/generic.c:192
 instrument_atomic_read include/linux/instrumented.h:56 [inline]
 atomic64_read include/asm-generic/atomic-instrumented.h:837 [inline]
 atomic_long_read include/asm-generic/atomic-long.h:29 [inline]
 __mutex_unlock_slowpath+0x88/0x590 kernel/locking/mutex.c:1237
 io_async_task_func+0x485/0x610 fs/io_uring.c:4689
 task_work_run+0x137/0x1c0 kernel/task_work.c:135
 tracehook_notify_resume include/linux/tracehook.h:188 [inline]
 exit_to_user_mode_loop kernel/entry/common.c:139 [inline]
 exit_to_user_mode_prepare+0xfa/0x1c0 kernel/entry/common.c:166
 syscall_exit_to_user_mode+0x5e/0x1a0 kernel/entry/common.c:241
 entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x45ce69
Code: 2d b6 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 0f 83 fb b5 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007f6719775c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000037
RAX: fffffffffffffffe RBX: 0000000000004f40 RCX: 000000000045ce69
RDX: 0000000000000043 RSI: 0000000000000000 RDI: 0000000000000006
RBP: 000000000118c010 R08: 0000000020000140 R09: 0000000000000000
R10: 0000000020000000 R11: 0000000000000246 R12: 000000000118bfcc
R13: 00007fff62cc118f R14: 00007f67197769c0 R15: 000000000118bfcc

Allocated by task 23153:
 kasan_save_stack mm/kasan/common.c:48 [inline]
 kasan_set_track mm/kasan/common.c:56 [inline]
 __kasan_kmalloc+0x100/0x130 mm/kasan/common.c:461
 kmem_cache_alloc_trace+0x1f6/0x2f0 mm/slab.c:3550
 kmalloc include/linux/slab.h:554 [inline]
 kzalloc include/linux/slab.h:666 [inline]
 io_ring_ctx_alloc fs/io_uring.c:1030 [inline]
 io_uring_create fs/io_uring.c:8308 [inline]
 io_uring_setup fs/io_uring.c:8401 [inline]
 __do_sys_io_uring_setup fs/io_uring.c:8407 [inline]
 __se_sys_io_uring_setup+0x5ce/0x2c70 fs/io_uring.c:8404
 do_syscall_64+0x31/0x70 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Freed by task 5:
 kasan_save_stack mm/kasan/common.c:48 [inline]
 kasan_set_track+0x3d/0x70 mm/kasan/common.c:56
 kasan_set_free_info+0x17/0x30 mm/kasan/generic.c:355
 __kasan_slab_free+0xdd/0x110 mm/kasan/common.c:422
 __cache_free mm/slab.c:3418 [inline]
 kfree+0x10a/0x220 mm/slab.c:3756
 process_one_work+0x789/0xfc0 kernel/workqueue.c:2269
 worker_thread+0xaa4/0x1460 kernel/workqueue.c:2415
 kthread+0x37e/0x3a0 drivers/block/aoe/aoecmd.c:1234
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:294

Last call_rcu():
 kasan_save_stack+0x27/0x50 mm/kasan/common.c:48
 kasan_record_aux_stack+0x7b/0xb0 mm/kasan/generic.c:346
 __call_rcu kernel/rcu/tree.c:2894 [inline]
 call_rcu+0x139/0x840 kernel/rcu/tree.c:2968
 __percpu_ref_switch_to_atomic lib/percpu-refcount.c:192 [inline]
 __percpu_ref_switch_mode+0x2c1/0x4f0 lib/percpu-refcount.c:237
 percpu_ref_kill_and_confirm+0x8f/0x130 lib/percpu-refcount.c:350
 percpu_ref_kill include/linux/percpu-refcount.h:136 [inline]
 io_ring_ctx_wait_and_kill+0x3c/0x570 fs/io_uring.c:7797
 io_uring_release+0x59/0x70 fs/io_uring.c:7829
 __fput+0x34f/0x7b0 fs/file_table.c:281
 task_work_run+0x137/0x1c0 kernel/task_work.c:135
 tracehook_notify_resume include/linux/tracehook.h:188 [inline]
 exit_to_user_mode_loop kernel/entry/common.c:139 [inline]
 exit_to_user_mode_prepare+0xfa/0x1c0 kernel/entry/common.c:166
 syscall_exit_to_user_mode+0x5e/0x1a0 kernel/entry/common.c:241
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Second to last call_rcu():
 kasan_save_stack+0x27/0x50 mm/kasan/common.c:48
 kasan_record_aux_stack+0x7b/0xb0 mm/kasan/generic.c:346
 __call_rcu kernel/rcu/tree.c:2894 [inline]
 call_rcu+0x139/0x840 kernel/rcu/tree.c:2968
 __percpu_ref_switch_to_atomic lib/percpu-refcount.c:192 [inline]
 __percpu_ref_switch_mode+0x2c1/0x4f0 lib/percpu-refcount.c:237
 percpu_ref_kill_and_confirm+0x8f/0x130 lib/percpu-refcount.c:350
 percpu_ref_kill include/linux/percpu-refcount.h:136 [inline]
 io_ring_ctx_wait_and_kill+0x3c/0x570 fs/io_uring.c:7797
 io_uring_release+0x59/0x70 fs/io_uring.c:7829
 __fput+0x34f/0x7b0 fs/file_table.c:281
 task_work_run+0x137/0x1c0 kernel/task_work.c:135
 tracehook_notify_resume include/linux/tracehook.h:188 [inline]
 exit_to_user_mode_loop kernel/entry/common.c:139 [inline]
 exit_to_user_mode_prepare+0xfa/0x1c0 kernel/entry/common.c:166
 syscall_exit_to_user_mode+0x5e/0x1a0 kernel/entry/common.c:241
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

The buggy address belongs to the object at ffff888095250000
 which belongs to the cache kmalloc-2k of size 2048
The buggy address is located 960 bytes inside of
 2048-byte region [ffff888095250000, ffff888095250800)
The buggy address belongs to the page:
page:000000005a2c89d9 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x95250
flags: 0xfffe0000000200(slab)
raw: 00fffe0000000200 ffffea00024ca6c8 ffffea00024d8c48 ffff8880aa440800
raw: 0000000000000000 ffff888095250000 0000000100000001 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff888095250280: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff888095250300: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff888095250380: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                           ^
 ffff888095250400: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff888095250480: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================

Crashes (1):
Manager	Time	Kernel	Commit	Syzkaller	Config	Log	Report	Syz repro	C repro	VM info	Maintainers
ci-upstream-kasan-gce-smack-root	2020/08/11 03:01	upstream	fc80c51f	7adc7b65	.config	log	report	syz			axboe@kernel.dk, io-uring@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, viro@zeniv.linux.org.uk