Re: [syzbot] KASAN: use-after-free Read in __post_watch_notification

syzbot
2022-07-28T02:46:22Z

Hello,

syzbot has tested the proposed patch but the reproducer is still triggering an issue:
KASAN: use-after-free Read in __post_watch_notification

==================================================================
BUG: KASAN: use-after-free in __post_watch_notification+0x1fe/0x900 kernel/watch_queue.c:221
Read of size 8 at addr ffff888021dc5410 by task syz-executor239/27731

CPU: 0 PID: 27731 Comm: syz-executor239 Not tainted 5.19.0-rc8-syzkaller-dirty #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 06/29/2022
Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:88 [inline]
dump_stack_lvl+0x1e3/0x2cb lib/dump_stack.c:106
print_address_description+0x65/0x4b0 mm/kasan/report.c:313
print_report+0xf4/0x210 mm/kasan/report.c:429
kasan_report+0xfb/0x130 mm/kasan/report.c:491
__post_watch_notification+0x1fe/0x900 kernel/watch_queue.c:221
post_watch_notification include/linux/watch_queue.h:109 [inline]
notify_key security/keys/internal.h:199 [inline]
__key_update+0x428/0x4e0 security/keys/key.c:775
key_create_or_update+0xa8f/0xd60 security/keys/key.c:979
__do_sys_add_key security/keys/keyctl.c:134 [inline]
__se_sys_add_key+0x338/0x480 security/keys/keyctl.c:74
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x2b/0x70 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x63/0xcd
RIP: 0033:0x7f503a6db9f9
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 11 15 00 00 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 73 01 c3 48 c7 c1 b8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f503a68d2f8 EFLAGS: 00000246 ORIG_RAX: 00000000000000f8
RAX: ffffffffffffffda RBX: 00007f503a763408 RCX: 00007f503a6db9f9
RDX: 00000000200000c0 RSI: 0000000020000080 RDI: 0000000020000040
RBP: 0000000000000000 R08: 00000000fffffffc R09: 0000000000000000
R10: 0000000000000048 R11: 0000000000000246 R12: 00007f503a763400
R13: 00007f503a76340c R14: 00007f503a731064 R15: 3a74707972637366
</TASK>

Allocated by task 27707:
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_kmalloc+0xdc/0x110 mm/kasan/common.c:515
kasan_kmalloc include/linux/kasan.h:234 [inline]
kmem_cache_alloc_trace+0x94/0x310 mm/slub.c:3284
kmalloc include/linux/slab.h:600 [inline]
kzalloc include/linux/slab.h:733 [inline]
watch_queue_init+0x4f/0x140 kernel/watch_queue.c:674
create_pipe_files+0x478/0x6e0 fs/pipe.c:921
__do_pipe_flags+0x46/0x200 fs/pipe.c:962
do_pipe2+0xd0/0x300 fs/pipe.c:1010
__do_sys_pipe2 fs/pipe.c:1028 [inline]
__se_sys_pipe2 fs/pipe.c:1026 [inline]
__x64_sys_pipe2+0x56/0x60 fs/pipe.c:1026
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x2b/0x70 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x63/0xcd

Freed by task 22:
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+0xd8/0x110 mm/kasan/common.c:366
kasan_slab_free include/linux/kasan.h:200 [inline]
slab_free_hook mm/slub.c:1754 [inline]
slab_free_freelist_hook+0x12e/0x1a0 mm/slub.c:1780
slab_free mm/slub.c:3536 [inline]
kmem_cache_free_bulk+0x105/0x1d0 mm/slub.c:3683
kfree_bulk include/linux/slab.h:456 [inline]
kfree_rcu_work+0x35b/0x7c0 kernel/rcu/tree.c:3370
process_one_work+0x81c/0xd10 kernel/workqueue.c:2289
worker_thread+0xb14/0x1330 kernel/workqueue.c:2436
kthread+0x266/0x300 kernel/kthread.c:376
ret_from_fork+0x1f/0x30

Last potentially related work creation:
kasan_save_stack+0x3b/0x60 mm/kasan/common.c:38
__kasan_record_aux_stack+0xaf/0xc0 mm/kasan/generic.c:348
kvfree_call_rcu+0x118/0x840 kernel/rcu/tree.c:3647
keyctl_watch_key+0x3d2/0x450 security/keys/keyctl.c:1839
__do_sys_keyctl security/keys/keyctl.c:2016 [inline]
__se_sys_keyctl+0x635/0xb60 security/keys/keyctl.c:1869
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x2b/0x70 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x63/0xcd

The buggy address belongs to the object at ffff888021dc5400
which belongs to the cache kmalloc-192 of size 192
The buggy address is located 16 bytes inside of
192-byte region [ffff888021dc5400, ffff888021dc54c0)

The buggy address belongs to the physical page:
page:ffffea0000877140 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x21dc5
flags: 0xfff00000000200(slab|node=0|zone=1|lastcpupid=0x7ff)
raw: 00fff00000000200 0000000000000000 dead000000000122 ffff888011c41a00
raw: 0000000000000000 0000000000100010 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 0, migratetype Unmovable, gfp_mask 0x112cc0(GFP_USER|__GFP_NOWARN|__GFP_NORETRY), pid 27704, tgid 27703 (syz-executor239), ts 435095125439, free_ts 435075154261
prep_new_page mm/page_alloc.c:2456 [inline]
get_page_from_freelist+0x72b/0x7a0 mm/page_alloc.c:4198
__alloc_pages+0x259/0x560 mm/page_alloc.c:5426
alloc_slab_page+0x70/0xf0 mm/slub.c:1824
allocate_slab+0x5e/0x520 mm/slub.c:1969
new_slab mm/slub.c:2029 [inline]
___slab_alloc+0x42e/0xce0 mm/slub.c:3031
__slab_alloc mm/slub.c:3118 [inline]
slab_alloc_node mm/slub.c:3209 [inline]
slab_alloc mm/slub.c:3251 [inline]
kmem_cache_alloc_trace+0x25c/0x310 mm/slub.c:3282
kmalloc include/linux/slab.h:600 [inline]
kzalloc include/linux/slab.h:733 [inline]
loopback_open+0x120/0xa20 sound/drivers/aloop.c:1192
snd_pcm_open_substream+0xd8b/0x1b70 sound/core/pcm_native.c:2739
snd_pcm_oss_open_file sound/core/oss/pcm_oss.c:2454 [inline]
snd_pcm_oss_open+0x1185/0x2060 sound/core/oss/pcm_oss.c:2535
chrdev_open+0x5fb/0x680 fs/char_dev.c:414
do_dentry_open+0x789/0x1040 fs/open.c:848
do_open fs/namei.c:3520 [inline]
path_openat+0x26c0/0x2ec0 fs/namei.c:3653
do_filp_open+0x277/0x4f0 fs/namei.c:3680
do_sys_openat2+0x13b/0x500 fs/open.c:1278
do_sys_open fs/open.c:1294 [inline]
__do_sys_openat fs/open.c:1310 [inline]
__se_sys_openat fs/open.c:1305 [inline]
__x64_sys_openat+0x243/0x290 fs/open.c:1305
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x2b/0x70 arch/x86/entry/common.c:80
page last free stack trace:
reset_page_owner include/linux/page_owner.h:24 [inline]
free_pages_prepare mm/page_alloc.c:1371 [inline]
free_pcp_prepare+0x812/0x900 mm/page_alloc.c:1421
free_unref_page_prepare mm/page_alloc.c:3343 [inline]
free_unref_page+0x7d/0x390 mm/page_alloc.c:3438
__vunmap+0x867/0x9d0 mm/vmalloc.c:2665
do_free_pages sound/core/pcm_memory.c:65 [inline]
snd_pcm_lib_free_pages+0x213/0x2e0 sound/core/pcm_memory.c:467
do_hw_free sound/core/pcm_native.c:876 [inline]
snd_pcm_release_substream+0x2cd/0x490 sound/core/pcm_native.c:2704
snd_pcm_oss_release_file sound/core/oss/pcm_oss.c:2413 [inline]
snd_pcm_oss_release+0x1a3/0x270 sound/core/oss/pcm_oss.c:2592
__fput+0x3b9/0x820 fs/file_table.c:317
task_work_run+0x146/0x1c0 kernel/task_work.c:177
resume_user_mode_work include/linux/resume_user_mode.h:49 [inline]
exit_to_user_mode_loop+0x134/0x160 kernel/entry/common.c:169
exit_to_user_mode_prepare+0xad/0x110 kernel/entry/common.c:201
__syscall_exit_to_user_mode_work kernel/entry/common.c:283 [inline]
syscall_exit_to_user_mode+0x2e/0x60 kernel/entry/common.c:294
entry_SYSCALL_64_after_hwframe+0x63/0xcd

Memory state around the buggy address:
ffff888021dc5300: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff888021dc5380: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
>ffff888021dc5400: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff888021dc5480: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
ffff888021dc5500: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================

Tested on:

commit: e0dccc3b Linux 5.19-rc8
git tree: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
console output: https://syzkaller.appspot.com/x/log.txt?x=123a0752080000
kernel config: https://syzkaller.appspot.com/x/.config?x=cfd2f9ae77f1f719
dashboard link: https://syzkaller.appspot.com/bug?extid=03d7b43290037d1f87ca
compiler: Debian clang version 13.0.1-++20220126092033+75e33f71c2da-1~exp1~20220126212112.63, GNU ld (GNU Binutils for Debian) 2.35.2
patch: https://syzkaller.appspot.com/x/patch.diff?x=17cb2102080000