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KASAN: use-after-free Read in kernfs_get (2)

Status: premoderation: reported syz repro on 2024/07/15 05:15
Bug presence: origin:lts
[Documentation on labels]
Reported-by: syzbot+796f6b9dffdc6fa01dfc@syzkaller.appspotmail.com
First crash: 354d, last: 6d20h
▶ ▼ Bug presence (2)
Date Name Commit Repro Result
2025/06/19 lts (merge base) 1c700860e8bc C [report] KASAN: use-after-free Read in kernfs_get
2025/06/19 upstream (ToT) fb4d33ab452e C Didn't crash
▶ ▼ Similar bugs (9)
Kernel Title Repro Cause bisect Fix bisect Count Last Reported Patched Status
android-6-1 KASAN: use-after-free Write in kernfs_get syz 8 58d 226d 0/2 premoderation: reported syz repro on 2024/11/19 13:51
upstream KASAN: use-after-free Read in kernfs_get kernfs 8 1086d 1207d 0/29 auto-obsoleted due to no activity on 2022/11/11 09:18
upstream KASAN: use-after-free Read in kernfs_get (2) kernfs 2 868d 954d 0/29 auto-obsoleted due to no activity on 2023/06/16 19:32
android-5-15 KASAN: use-after-free Read in kernfs_get 3 865d 989d 0/2 auto-obsoleted due to no activity on 2023/05/20 22:47
android-6-1 KASAN: use-after-free Read in kernfs_get 2 325d 370d 0/2 auto-obsoleted due to no activity on 2024/11/11 11:50
linux-5.15 KASAN: use-after-free Read in kernfs_get 1 323d 323d 0/3 auto-obsoleted due to no activity on 2024/11/23 10:42
upstream KASAN: slab-use-after-free Read in kernfs_get kernfs 1 504d 504d 0/29 auto-obsoleted due to no activity on 2024/05/26 00:41
android-5-15 KASAN: use-after-free Write in kernfs_get 3 619d 707d 0/2 auto-obsoleted due to no activity on 2024/01/21 14:31
upstream KASAN: slab-use-after-free Read in kernfs_get (2) kernfs 2 221d 218d 0/29 auto-obsoleted due to no activity on 2025/03/04 15:25
▶ ▼ Last patch testing requests (1)
Created Duration User Patch Repo Result
2025/06/27 14:53 16m retest repro android13-5.15-lts report log

Sample crash report:
==================================================================
BUG: KASAN: use-after-free in instrument_atomic_read_write include/linux/instrumented.h:101 [inline]
BUG: KASAN: use-after-free in atomic_inc include/linux/atomic/atomic-instrumented.h:181 [inline]
BUG: KASAN: use-after-free in kernfs_get+0x5e/0x90 fs/kernfs/dir.c:505
Write of size 4 at addr ffff888122ad1640 by task kworker/0:0/6

CPU: 0 PID: 6 Comm: kworker/0:0 Not tainted 5.15.185-syzkaller-00339-ge678c93d43cc #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
Workqueue: events flush_stashed_error_work
Call Trace:
 <TASK>
 __dump_stack+0x21/0x30 lib/dump_stack.c:88
 dump_stack_lvl+0xee/0x150 lib/dump_stack.c:106
 print_address_description+0x7f/0x2c0 mm/kasan/report.c:248
 __kasan_report mm/kasan/report.c:427 [inline]
 kasan_report+0xf1/0x140 mm/kasan/report.c:444
 check_region_inline mm/kasan/generic.c:-1 [inline]
 kasan_check_range+0x280/0x290 mm/kasan/generic.c:189
 __kasan_check_write+0x14/0x20 mm/kasan/shadow.c:37
 instrument_atomic_read_write include/linux/instrumented.h:101 [inline]
 atomic_inc include/linux/atomic/atomic-instrumented.h:181 [inline]
 kernfs_get+0x5e/0x90 fs/kernfs/dir.c:505
 sysfs_notify+0x5a/0xd0 fs/sysfs/file.c:190
 ext4_notify_error_sysfs+0x25/0x30 fs/ext4/sysfs.c:516
 flush_stashed_error_work+0x2d5/0x2f0 fs/ext4/super.c:-1
 process_one_work+0x6be/0xba0 kernel/workqueue.c:2325
 worker_thread+0xa59/0x1200 kernel/workqueue.c:2472
 kthread+0x411/0x500 kernel/kthread.c:337
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:287
 </TASK>

Allocated by task 1006:
 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:433 [inline]
 __kasan_slab_alloc+0xbd/0xf0 mm/kasan/common.c:466
 kasan_slab_alloc include/linux/kasan.h:217 [inline]
 slab_post_alloc_hook+0x4f/0x2b0 mm/slab.h:550
 slab_alloc_node mm/slub.c:3240 [inline]
 slab_alloc mm/slub.c:3250 [inline]
 kmem_cache_alloc+0xf7/0x260 mm/slub.c:3255
 kmem_cache_zalloc include/linux/slab.h:737 [inline]
 __kernfs_new_node+0xdb/0x680 fs/kernfs/dir.c:593
 kernfs_new_node+0x150/0x260 fs/kernfs/dir.c:669
 kernfs_create_dir_ns+0x47/0x130 fs/kernfs/dir.c:1017
 sysfs_create_dir_ns+0x11c/0x280 fs/sysfs/dir.c:59
 create_dir lib/kobject.c:89 [inline]
 kobject_add_internal+0x755/0xda0 lib/kobject.c:263
 kobject_add_varg lib/kobject.c:398 [inline]
 kobject_init_and_add+0x122/0x190 lib/kobject.c:481
 ext4_register_sysfs+0xbb/0x2c0 fs/ext4/sysfs.c:529
 ext4_fill_super+0x863b/0x9030 fs/ext4/super.c:4941
 mount_bdev+0x2ae/0x3e0 fs/super.c:1400
 ext4_mount+0x34/0x40 fs/ext4/super.c:6618
 legacy_get_tree+0xed/0x190 fs/fs_context.c:611
 vfs_get_tree+0x89/0x260 fs/super.c:1530
 do_new_mount+0x25a/0xa20 fs/namespace.c:3010
 path_mount+0x675/0x1020 fs/namespace.c:3340
 do_mount fs/namespace.c:3353 [inline]
 __do_sys_mount fs/namespace.c:3561 [inline]
 __se_sys_mount+0x318/0x380 fs/namespace.c:3538
 __x64_sys_mount+0xbf/0xd0 fs/namespace.c:3538
 x64_sys_call+0x6bf/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:166
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x66/0xd0

Freed by task 1006:
 kasan_save_stack mm/kasan/common.c:38 [inline]
 kasan_set_track+0x4a/0x70 mm/kasan/common.c:45
 kasan_set_free_info+0x23/0x40 mm/kasan/generic.c:370
 ____kasan_slab_free+0x125/0x160 mm/kasan/common.c:365
 __kasan_slab_free+0x11/0x20 mm/kasan/common.c:373
 kasan_slab_free include/linux/kasan.h:193 [inline]
 slab_free_hook mm/slub.c:1723 [inline]
 slab_free_freelist_hook+0xc2/0x190 mm/slub.c:1749
 slab_free mm/slub.c:3521 [inline]
 kmem_cache_free+0x100/0x320 mm/slub.c:3539
 kernfs_put+0x310/0x480 fs/kernfs/dir.c:547
 sysfs_put include/linux/sysfs.h:641 [inline]
 __kobject_del+0xf8/0x2f0 lib/kobject.c:629
 kobject_del+0x45/0x60 lib/kobject.c:651
 ext4_unregister_sysfs+0x91/0xa0 fs/ext4/sysfs.c:563
 ext4_put_super+0x70/0xa70 fs/ext4/super.c:1183
 generic_shutdown_super+0x151/0x330 fs/super.c:475
 kill_block_super+0x7f/0xf0 fs/super.c:1427
 deactivate_locked_super+0xa0/0x100 fs/super.c:335
 deactivate_super+0xaf/0xe0 fs/super.c:366
 cleanup_mnt+0x446/0x500 fs/namespace.c:1139
 __cleanup_mnt+0x19/0x20 fs/namespace.c:1146
 task_work_run+0x127/0x190 kernel/task_work.c:188
 tracehook_notify_resume include/linux/tracehook.h:189 [inline]
 exit_to_user_mode_loop+0xd0/0xe0 kernel/entry/common.c:181
 exit_to_user_mode_prepare+0x5a/0xa0 kernel/entry/common.c:214
 __syscall_exit_to_user_mode_work kernel/entry/common.c:296 [inline]
 syscall_exit_to_user_mode+0x1a/0x30 kernel/entry/common.c:307
 do_syscall_64+0x58/0xa0 arch/x86/entry/common.c:86
 entry_SYSCALL_64_after_hwframe+0x66/0xd0

The buggy address belongs to the object at ffff888122ad1640
 which belongs to the cache kernfs_node_cache of size 136
The buggy address is located 0 bytes inside of
 136-byte region [ffff888122ad1640, ffff888122ad16c8)
The buggy address belongs to the page:
page:ffffea00048ab440 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x122ad1
flags: 0x4000000000000200(slab|zone=1)
raw: 4000000000000200 ffffea00048a8080 0000000900000004 ffff8881001c5500
raw: 0000000000000000 0000000000140014 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 312, ts 45073696707, free_ts 44104701809
 set_page_owner include/linux/page_owner.h:33 [inline]
 post_alloc_hook+0x192/0x1b0 mm/page_alloc.c:2605
 prep_new_page+0x1c/0x110 mm/page_alloc.c:2611
 get_page_from_freelist+0x2cc5/0x2d50 mm/page_alloc.c:4485
 __alloc_pages+0x18f/0x440 mm/page_alloc.c:5789
 alloc_slab_page mm/slub.c:-1 [inline]
 allocate_slab mm/slub.c:1932 [inline]
 new_slab+0xa1/0x4d0 mm/slub.c:1995
 ___slab_alloc+0x381/0x810 mm/slub.c:3028
 __slab_alloc+0x49/0x90 mm/slub.c:3115
 slab_alloc_node mm/slub.c:3206 [inline]
 slab_alloc mm/slub.c:3250 [inline]
 kmem_cache_alloc+0x138/0x260 mm/slub.c:3255
 kmem_cache_zalloc include/linux/slab.h:737 [inline]
 __kernfs_new_node+0xdb/0x680 fs/kernfs/dir.c:593
 kernfs_new_node+0x150/0x260 fs/kernfs/dir.c:669
 __kernfs_create_file+0x4e/0x270 fs/kernfs/file.c:987
 sysfs_add_file_mode_ns+0x29a/0x350 fs/sysfs/file.c:317
 create_files fs/sysfs/group.c:64 [inline]
 internal_create_group+0x489/0xcf0 fs/sysfs/group.c:149
 internal_create_groups fs/sysfs/group.c:189 [inline]
 sysfs_create_groups+0x58/0x120 fs/sysfs/group.c:215
 device_add_groups drivers/base/core.c:2501 [inline]
 device_add_attrs+0x155/0x700 drivers/base/core.c:2660
 device_add+0x5e3/0xed0 drivers/base/core.c:3373
page last free stack trace:
 reset_page_owner include/linux/page_owner.h:26 [inline]
 free_pages_prepare mm/page_alloc.c:1472 [inline]
 free_pcp_prepare mm/page_alloc.c:1544 [inline]
 free_unref_page_prepare+0x542/0x550 mm/page_alloc.c:3534
 free_unref_page+0xa2/0x550 mm/page_alloc.c:3616
 free_the_page mm/page_alloc.c:805 [inline]
 __free_pages+0x6c/0x100 mm/page_alloc.c:5865
 __vunmap+0x84d/0x9e0 mm/vmalloc.c:2652
 __vfree mm/vmalloc.c:2701 [inline]
 vfree+0x8b/0xc0 mm/vmalloc.c:2732
 kcov_put kernel/kcov.c:417 [inline]
 kcov_close+0x2b/0x50 kernel/kcov.c:519
 __fput+0x20b/0x8b0 fs/file_table.c:311
 ____fput+0x15/0x20 fs/file_table.c:339
 task_work_run+0x127/0x190 kernel/task_work.c:188
 tracehook_notify_resume include/linux/tracehook.h:189 [inline]
 exit_to_user_mode_loop+0xd0/0xe0 kernel/entry/common.c:181
 exit_to_user_mode_prepare+0x5a/0xa0 kernel/entry/common.c:214
 __syscall_exit_to_user_mode_work kernel/entry/common.c:296 [inline]
 syscall_exit_to_user_mode+0x1a/0x30 kernel/entry/common.c:307
 do_syscall_64+0x58/0xa0 arch/x86/entry/common.c:86
 entry_SYSCALL_64_after_hwframe+0x66/0xd0

Memory state around the buggy address:
 ffff888122ad1500: fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc fa
 ffff888122ad1580: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff888122ad1600: fc fc fc fc fc fc fc fc fa fb fb fb fb fb fb fb
                                           ^
 ffff888122ad1680: fb fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc
 ffff888122ad1700: fc fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================
general protection fault, probably for non-canonical address 0xf2a3fc29e0000087: 0000 [#1] PREEMPT SMP KASAN
KASAN: maybe wild-memory-access in range [0x9520014f00000438-0x9520014f0000043f]
CPU: 0 PID: 6 Comm: kworker/0:0 Tainted: G    B             5.15.185-syzkaller-00339-ge678c93d43cc #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
Workqueue: events flush_stashed_error_work
RIP: 0010:kernfs_root fs/kernfs/kernfs-internal.h:50 [inline]
RIP: 0010:kernfs_find_and_get_ns+0x54/0x110 fs/kernfs/dir.c:884
Code: 48 89 f8 48 c1 e8 03 42 80 3c 28 00 74 05 e8 73 a3 d8 ff 49 8b 5c 24 08 48 85 db 49 0f 44 dc 48 83 c3 50 48 89 d8 48 c1 e8 03 <42> 80 3c 28 00 74 08 48 89 df e8 4d a3 d8 ff 48 8b 1b 48 83 c3 68
RSP: 0018:ffffc90000067c60 EFLAGS: 00010a07
RAX: 12a40029e0000087 RBX: 9520014f0000043e RCX: ffffffff81ce74ed
RDX: 0000000000000000 RSI: 0000000000000008 RDI: ffff888122ad1648
RBP: ffffc90000067c88 R08: 0000000000000004 R09: 0000000000000003
R10: fffffbfff0e17a4c R11: 1ffffffff0e17a4c R12: ffff888122ad1640
R13: dffffc0000000000 R14: 0000000000000000 R15: ffffffff854f0360
FS:  0000000000000000(0000) GS:ffff8881f7000000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f9c0032c000 CR3: 0000000107ddf000 CR4: 00000000003506b0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 kernfs_find_and_get include/linux/kernfs.h:574 [inline]
 sysfs_notify+0x71/0xd0 fs/sysfs/file.c:193
 ext4_notify_error_sysfs+0x25/0x30 fs/ext4/sysfs.c:516
 flush_stashed_error_work+0x2d5/0x2f0 fs/ext4/super.c:-1
 process_one_work+0x6be/0xba0 kernel/workqueue.c:2325
 worker_thread+0xa59/0x1200 kernel/workqueue.c:2472
 kthread+0x411/0x500 kernel/kthread.c:337
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:287
 </TASK>
Modules linked in:
---[ end trace 53ff12f503bedc29 ]---
RIP: 0010:kernfs_root fs/kernfs/kernfs-internal.h:50 [inline]
RIP: 0010:kernfs_find_and_get_ns+0x54/0x110 fs/kernfs/dir.c:884
Code: 48 89 f8 48 c1 e8 03 42 80 3c 28 00 74 05 e8 73 a3 d8 ff 49 8b 5c 24 08 48 85 db 49 0f 44 dc 48 83 c3 50 48 89 d8 48 c1 e8 03 <42> 80 3c 28 00 74 08 48 89 df e8 4d a3 d8 ff 48 8b 1b 48 83 c3 68
RSP: 0018:ffffc90000067c60 EFLAGS: 00010a07

RAX: 12a40029e0000087 RBX: 9520014f0000043e RCX: ffffffff81ce74ed
RDX: 0000000000000000 RSI: 0000000000000008 RDI: ffff888122ad1648
RBP: ffffc90000067c88 R08: 0000000000000004 R09: 0000000000000003
R10: fffffbfff0e17a4c R11: 1ffffffff0e17a4c R12: ffff888122ad1640
R13: dffffc0000000000 R14: 0000000000000000 R15: ffffffff854f0360
FS:  0000000000000000(0000) GS:ffff8881f7000000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f6792532000 CR3: 000000010c739000 CR4: 00000000003506b0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
----------------
Code disassembly (best guess):
   0:	48 89 f8             	mov    %rdi,%rax
   3:	48 c1 e8 03          	shr    $0x3,%rax
   7:	42 80 3c 28 00       	cmpb   $0x0,(%rax,%r13,1)
   c:	74 05                	je     0x13
   e:	e8 73 a3 d8 ff       	call   0xffd8a386
  13:	49 8b 5c 24 08       	mov    0x8(%r12),%rbx
  18:	48 85 db             	test   %rbx,%rbx
  1b:	49 0f 44 dc          	cmove  %r12,%rbx
  1f:	48 83 c3 50          	add    $0x50,%rbx
  23:	48 89 d8             	mov    %rbx,%rax
  26:	48 c1 e8 03          	shr    $0x3,%rax
* 2a:	42 80 3c 28 00       	cmpb   $0x0,(%rax,%r13,1) <-- trapping instruction
  2f:	74 08                	je     0x39
  31:	48 89 df             	mov    %rbx,%rdi
  34:	e8 4d a3 d8 ff       	call   0xffd8a386
  39:	48 8b 1b             	mov    (%rbx),%rbx
  3c:	48 83 c3 68          	add    $0x68,%rbx

Crashes (20):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2025/06/12 17:27 android13-5.15-lts e678c93d43cc 98683f8f .config console log report syz / log [disk image] [vmlinux] [kernel image] [mounted in repro (corrupt fs)] ci2-android-5-15 KASAN: use-after-free Write in kernfs_get
2025/06/12 14:51 android13-5.15-lts e678c93d43cc 98683f8f .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-15 KASAN: use-after-free Read in kernfs_get
2025/06/10 01:25 android13-5.15-lts e678c93d43cc 4826c28e .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-15 KASAN: use-after-free Read in kernfs_get
2025/05/04 13:28 android13-5.15-lts 88c4075c39ed b0714e37 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-15 KASAN: use-after-free Read in kernfs_get
2025/03/19 14:44 android13-5.15-lts 7d1f9b5c2ff5 8d0a2921 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-15 KASAN: use-after-free Read in kernfs_get
2025/02/10 20:11 android13-5.15-lts 058abb720bd1 43f51a00 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-15 KASAN: use-after-free Read in kernfs_get
2025/01/09 05:03 android13-5.15-lts 19092c8155b4 f3558dbf .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-15 KASAN: use-after-free Read in kernfs_get
2024/11/10 08:08 android13-5.15-lts 5e4635681cf1 6b856513 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-15 KASAN: use-after-free Read in kernfs_get
2024/09/12 06:58 android13-5.15-lts e6fb3b0fa87f d94c83d8 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-15 KASAN: use-after-free Read in kernfs_get
2024/09/10 04:33 android13-5.15-lts c53388f01037 784df80e .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-15 KASAN: use-after-free Read in kernfs_get
2024/08/30 22:23 android13-5.15-lts 29d153aabd54 1eda0d14 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-15 KASAN: use-after-free Read in kernfs_get
2024/07/15 05:14 android13-5.15-lts db06c48ab67e eaeb5c15 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-15 KASAN: use-after-free Read in kernfs_get
2025/05/22 16:31 android13-5.15-lts 56993594bfa4 0919b50b .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-15 KASAN: use-after-free Write in kernfs_get
2025/03/19 14:41 android13-5.15-lts 7d1f9b5c2ff5 8d0a2921 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-15 KASAN: use-after-free Write in kernfs_get
2025/01/21 03:35 android13-5.15-lts 829d9f138569 6e87cfa2 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-15 KASAN: use-after-free Write in kernfs_get
2025/01/17 08:23 android13-5.15-lts 829d9f138569 f9e07a6e .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-15 KASAN: use-after-free Write in kernfs_get
2025/01/14 10:09 android13-5.15-lts 829d9f138569 b1f1cd88 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-15 KASAN: use-after-free Write in kernfs_get
2024/12/03 22:26 android13-5.15-lts fa1d8b6c5d4d b50eb251 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-15 KASAN: use-after-free Write in kernfs_get
2024/10/15 17:27 android13-5.15-lts 5e4635681cf1 7eb57b4a .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-15 KASAN: use-after-free Write in kernfs_get
2024/08/31 05:26 android13-5.15-lts 29d153aabd54 1eda0d14 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-15 KASAN: use-after-free Write in kernfs_get
* Struck through repros no longer work on HEAD.