syzbot

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WARNING: CPU: 1 PID: 384 at fs/inode.c:340 drop_nlink+0xce/0x110 fs/inode.c:340
Modules linked in:
CPU: 1 UID: 0 PID: 384 Comm: syz.2.17 Not tainted syzkaller #0 001c7e68fa735976e9f6b7ad125989e1d2b10b0e
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
RIP: 0010:drop_nlink+0xce/0x110 fs/inode.c:340
Code: 04 00 00 be 08 00 00 00 e8 bf 25 ee ff f0 48 ff 83 b8 04 00 00 5b 41 5c 41 5d 41 5e 41 5f 5d c3 cc cc cc cc cc e8 e2 5b 96 ff <0f> 0b eb 81 44 89 f1 80 e1 07 80 c1 03 38 c1 0f 8c 59 ff ff ff 4c
RSP: 0018:ffffc900007ef820 EFLAGS: 00010293
RAX: ffffffff81f1412e RBX: ffff888112c516c0 RCX: ffff8881158b3900
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: ffffc900007ef848 R08: 0000000000000003 R09: 0000000000000004
R10: dffffc0000000000 R11: fffff520000fdefc R12: dffffc0000000000
R13: 1ffff1102258a2e1 R14: ffff888112c51708 R15: 0000000000000000
FS:  0000000000000000(0000) GS:ffff8881f6f00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000000c0076af000 CR3: 0000000102764000 CR4: 00000000003526b0
Call Trace:
 <TASK>
 simple_rmdir+0x153/0x260 fs/libfs.c:773
 vfs_rmdir+0x3e0/0x560 fs/namei.c:4348
 incfs_kill_sb+0x109/0x230 fs/incfs/vfs.c:1968
 deactivate_locked_super+0xd8/0x2a0 fs/super.c:476
 deactivate_super+0xb8/0xe0 fs/super.c:509
 cleanup_mnt+0x406/0x4a0 fs/namespace.c:1380
 __cleanup_mnt+0x1d/0x40 fs/namespace.c:1387
 task_work_run+0x1e5/0x260 kernel/task_work.c:246
 exit_task_work include/linux/task_work.h:43 [inline]
 do_exit+0x9e3/0x2650 kernel/exit.c:953
 do_group_exit+0x229/0x2f0 kernel/exit.c:1095
 get_signal+0x1398/0x14e0 kernel/signal.c:2933
 arch_do_signal_or_restart+0xbc/0x760 arch/x86/kernel/signal.c:337
 exit_to_user_mode_loop kernel/entry/common.c:111 [inline]
 exit_to_user_mode_prepare include/linux/entry-common.h:328 [inline]
 irqentry_exit_to_user_mode+0x4d/0xb0 kernel/entry/common.c:231
 irqentry_exit+0x16/0x60 kernel/entry/common.c:334
 exc_page_fault+0x65/0xc0 arch/x86/mm/fault.c:1542
 asm_exc_page_fault+0x2b/0x30 arch/x86/include/asm/idtentry.h:623
RIP: 0033:0x7fa0bea514f7
Code: Unable to access opcode bytes at 0x7fa0bea514cd.
RSP: 002b:00007ffde1beb660 EFLAGS: 00010206
RAX: 0000000000000000 RBX: 000000000000000b RCX: 00007fa0beb9aeb9
RDX: 00007ffde1beb680 RSI: 00007ffde1beb7b0 RDI: 000000000000000b
RBP: 00007fa0bec08c1f R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000206 R12: 0000000000000000
R13: 00007fa0bee15fac R14: 00007fa0bee15fa0 R15: 00007fa0bee15fa0
 </TASK>
---[ end trace 0000000000000000 ]---
==================================================================
BUG: KASAN: null-ptr-deref in instrument_atomic_read_write include/linux/instrumented.h:96 [inline]
BUG: KASAN: null-ptr-deref in atomic_inc_return include/linux/atomic/atomic-instrumented.h:453 [inline]
BUG: KASAN: null-ptr-deref in ihold+0x24/0x70 fs/inode.c:452
Write of size 4 at addr 0000000000000168 by task syz.2.17/384

CPU: 1 UID: 0 PID: 384 Comm: syz.2.17 Tainted: G        W          syzkaller #0 001c7e68fa735976e9f6b7ad125989e1d2b10b0e
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
Call Trace:
 <TASK>
 __dump_stack+0x21/0x30 lib/dump_stack.c:94
 dump_stack_lvl+0x140/0x1c0 lib/dump_stack.c:120
 print_report+0x3d/0x70 mm/kasan/report.c:484
 kasan_report+0x162/0x1a0 mm/kasan/report.c:594
 check_region_inline mm/kasan/generic.c:-1 [inline]
 kasan_check_range+0x25a/0x2b0 mm/kasan/generic.c:189
 __kasan_check_write+0x18/0x20 mm/kasan/shadow.c:37
 instrument_atomic_read_write include/linux/instrumented.h:96 [inline]
 atomic_inc_return include/linux/atomic/atomic-instrumented.h:453 [inline]
 ihold+0x24/0x70 fs/inode.c:452
 d_delete_notify include/linux/fsnotify.h:357 [inline]
 vfs_rmdir+0x26a/0x560 fs/namei.c:4361
 incfs_kill_sb+0x109/0x230 fs/incfs/vfs.c:1968
 deactivate_locked_super+0xd8/0x2a0 fs/super.c:476
 deactivate_super+0xb8/0xe0 fs/super.c:509
 cleanup_mnt+0x406/0x4a0 fs/namespace.c:1380
 __cleanup_mnt+0x1d/0x40 fs/namespace.c:1387
 task_work_run+0x1e5/0x260 kernel/task_work.c:246
 exit_task_work include/linux/task_work.h:43 [inline]
 do_exit+0x9e3/0x2650 kernel/exit.c:953
 do_group_exit+0x229/0x2f0 kernel/exit.c:1095
 get_signal+0x1398/0x14e0 kernel/signal.c:2933
 arch_do_signal_or_restart+0xbc/0x760 arch/x86/kernel/signal.c:337
 exit_to_user_mode_loop kernel/entry/common.c:111 [inline]
 exit_to_user_mode_prepare include/linux/entry-common.h:328 [inline]
 irqentry_exit_to_user_mode+0x4d/0xb0 kernel/entry/common.c:231
 irqentry_exit+0x16/0x60 kernel/entry/common.c:334
 exc_page_fault+0x65/0xc0 arch/x86/mm/fault.c:1542
 asm_exc_page_fault+0x2b/0x30 arch/x86/include/asm/idtentry.h:623
RIP: 0033:0x7fa0bea514f7
Code: Unable to access opcode bytes at 0x7fa0bea514cd.
RSP: 002b:00007ffde1beb660 EFLAGS: 00010206
RAX: 0000000000000000 RBX: 000000000000000b RCX: 00007fa0beb9aeb9
RDX: 00007ffde1beb680 RSI: 00007ffde1beb7b0 RDI: 000000000000000b
RBP: 00007fa0bec08c1f R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000206 R12: 0000000000000000
R13: 00007fa0bee15fac R14: 00007fa0bee15fa0 R15: 00007fa0bee15fa0
 </TASK>
==================================================================
BUG: kernel NULL pointer dereference, address: 0000000000000168
#PF: supervisor write access in kernel mode
#PF: error_code(0x0002) - not-present page
PGD 0 P4D 0 
Oops: Oops: 0002 [#1] PREEMPT SMP KASAN PTI
CPU: 0 UID: 0 PID: 384 Comm: syz.2.17 Tainted: G    B   W          syzkaller #0 001c7e68fa735976e9f6b7ad125989e1d2b10b0e
Tainted: [B]=BAD_PAGE, [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
RIP: 0010:arch_atomic_add_return arch/x86/include/asm/atomic.h:85 [inline]
RIP: 0010:raw_atomic_add_return include/linux/atomic/atomic-arch-fallback.h:564 [inline]
RIP: 0010:raw_atomic_inc_return include/linux/atomic/atomic-arch-fallback.h:1020 [inline]
RIP: 0010:atomic_inc_return include/linux/atomic/atomic-instrumented.h:454 [inline]
RIP: 0010:ihold+0x2a/0x70 fs/inode.c:452
Code: f3 0f 1e fa 55 48 89 e5 41 56 53 48 89 fb e8 cd 52 96 ff 48 8d bb 68 01 00 00 be 04 00 00 00 e8 7c 1c ee ff 41 be 01 00 00 00 <f0> 44 0f c1 b3 68 01 00 00 41 ff c6 bf 02 00 00 00 44 89 f6 e8 dd
RSP: 0018:ffffc900007ef880 EFLAGS: 00010246
RAX: ffff8881158b3900 RBX: 0000000000000000 RCX: ffff8881158b3900
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: ffffc900007ef890 R08: ffffffff88b8b947 R09: 1ffffffff1171728
R10: dffffc0000000000 R11: fffffbfff1171729 R12: ffff888112c516cc
R13: 0000000000000000 R14: 0000000000000001 R15: 0000000000000000
FS:  0000000000000000(0000) GS:ffff8881f6e00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000168 CR3: 000000010bf90000 CR4: 00000000003526b0
Call Trace:
 <TASK>
 d_delete_notify include/linux/fsnotify.h:357 [inline]
 vfs_rmdir+0x26a/0x560 fs/namei.c:4361
 incfs_kill_sb+0x109/0x230 fs/incfs/vfs.c:1968
 deactivate_locked_super+0xd8/0x2a0 fs/super.c:476
 deactivate_super+0xb8/0xe0 fs/super.c:509
 cleanup_mnt+0x406/0x4a0 fs/namespace.c:1380
 __cleanup_mnt+0x1d/0x40 fs/namespace.c:1387
 task_work_run+0x1e5/0x260 kernel/task_work.c:246
 exit_task_work include/linux/task_work.h:43 [inline]
 do_exit+0x9e3/0x2650 kernel/exit.c:953
 do_group_exit+0x229/0x2f0 kernel/exit.c:1095
 get_signal+0x1398/0x14e0 kernel/signal.c:2933
 arch_do_signal_or_restart+0xbc/0x760 arch/x86/kernel/signal.c:337
 exit_to_user_mode_loop kernel/entry/common.c:111 [inline]
 exit_to_user_mode_prepare include/linux/entry-common.h:328 [inline]
 irqentry_exit_to_user_mode+0x4d/0xb0 kernel/entry/common.c:231
 irqentry_exit+0x16/0x60 kernel/entry/common.c:334
 exc_page_fault+0x65/0xc0 arch/x86/mm/fault.c:1542
 asm_exc_page_fault+0x2b/0x30 arch/x86/include/asm/idtentry.h:623
RIP: 0033:0x7fa0bea514f7
Code: Unable to access opcode bytes at 0x7fa0bea514cd.
RSP: 002b:00007ffde1beb660 EFLAGS: 00010206
RAX: 0000000000000000 RBX: 000000000000000b RCX: 00007fa0beb9aeb9
RDX: 00007ffde1beb680 RSI: 00007ffde1beb7b0 RDI: 000000000000000b
RBP: 00007fa0bec08c1f R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000206 R12: 0000000000000000
R13: 00007fa0bee15fac R14: 00007fa0bee15fa0 R15: 00007fa0bee15fa0
 </TASK>
Modules linked in:
CR2: 0000000000000168
---[ end trace 0000000000000000 ]---
RIP: 0010:arch_atomic_add_return arch/x86/include/asm/atomic.h:85 [inline]
RIP: 0010:raw_atomic_add_return include/linux/atomic/atomic-arch-fallback.h:564 [inline]
RIP: 0010:raw_atomic_inc_return include/linux/atomic/atomic-arch-fallback.h:1020 [inline]
RIP: 0010:atomic_inc_return include/linux/atomic/atomic-instrumented.h:454 [inline]
RIP: 0010:ihold+0x2a/0x70 fs/inode.c:452
Code: f3 0f 1e fa 55 48 89 e5 41 56 53 48 89 fb e8 cd 52 96 ff 48 8d bb 68 01 00 00 be 04 00 00 00 e8 7c 1c ee ff 41 be 01 00 00 00 <f0> 44 0f c1 b3 68 01 00 00 41 ff c6 bf 02 00 00 00 44 89 f6 e8 dd
RSP: 0018:ffffc900007ef880 EFLAGS: 00010246
RAX: ffff8881158b3900 RBX: 0000000000000000 RCX: ffff8881158b3900
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: ffffc900007ef890 R08: ffffffff88b8b947 R09: 1ffffffff1171728
R10: dffffc0000000000 R11: fffffbfff1171729 R12: ffff888112c516cc
R13: 0000000000000000 R14: 0000000000000001 R15: 0000000000000000
FS:  0000000000000000(0000) GS:ffff8881f6e00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000168 CR3: 000000010bf90000 CR4: 00000000003526b0
----------------
Code disassembly (best guess):
   0:	f3 0f 1e fa          	endbr64
   4:	55                   	push   %rbp
   5:	48 89 e5             	mov    %rsp,%rbp
   8:	41 56                	push   %r14
   a:	53                   	push   %rbx
   b:	48 89 fb             	mov    %rdi,%rbx
   e:	e8 cd 52 96 ff       	call   0xff9652e0
  13:	48 8d bb 68 01 00 00 	lea    0x168(%rbx),%rdi
  1a:	be 04 00 00 00       	mov    $0x4,%esi
  1f:	e8 7c 1c ee ff       	call   0xffee1ca0
  24:	41 be 01 00 00 00    	mov    $0x1,%r14d
* 2a:	f0 44 0f c1 b3 68 01 	lock xadd %r14d,0x168(%rbx) <-- trapping instruction
  31:	00 00
  33:	41 ff c6             	inc    %r14d
  36:	bf 02 00 00 00       	mov    $0x2,%edi
  3b:	44 89 f6             	mov    %r14d,%esi
  3e:	e8                   	.byte 0xe8
  3f:	dd                   	.byte 0xdd