syzbot

R10: 0000000000000000 R11: 0000000000000246 R12: 00007ffcec9735e0
R13: 00007ff19f825f90 R14: 000055556b7154e8 R15: 00007ffcec9746b0
 </TASK>
---[ end trace 7e986cb685b40015 ]---
==================================================================
BUG: KASAN: use-after-free in fast_dput+0x1e9/0x290 fs/dcache.c:753
Read of size 4 at addr ffff888129928770 by task syz-executor/835

CPU: 0 PID: 835 Comm: syz-executor Tainted: G        W         syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026
Call Trace:
 <TASK>
 __dump_stack+0x21/0x30 lib/dump_stack.c:88
 dump_stack_lvl+0x110/0x170 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
 __asan_report_load4_noabort+0x14/0x20 mm/kasan/report_generic.c:308
 fast_dput+0x1e9/0x290 fs/dcache.c:753
 dput+0x26/0x90 fs/dcache.c:880
 incfs_free_mount_info+0x60/0x200 fs/incfs/data_mgmt.c:166
 incfs_kill_sb+0x1b8/0x220 fs/incfs/vfs.c:1997
 deactivate_locked_super+0xa0/0x100 fs/super.c:335
 deactivate_super+0xaf/0xe0 fs/super.c:366
 cleanup_mnt+0x45b/0x510 fs/namespace.c:1148
 __cleanup_mnt+0x19/0x20 fs/namespace.c:1155
 task_work_run+0x127/0x190 kernel/task_work.c:188
 exit_task_work include/linux/task_work.h:33 [inline]
 do_exit+0xa9e/0x27e0 kernel/exit.c:889
 do_group_exit+0x141/0x310 kernel/exit.c:1003
 __do_sys_exit_group kernel/exit.c:1014 [inline]
 __se_sys_exit_group kernel/exit.c:1012 [inline]
 __x64_sys_exit_group+0x3f/0x40 kernel/exit.c:1012
 x64_sys_call+0x832/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:232
 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
RIP: 0033:0x7ff19f790799
Code: Unable to access opcode bytes at RIP 0x7ff19f79076f.
RSP: 002b:00007ffcec972328 EFLAGS: 00000246 ORIG_RAX: 00000000000000e7
RAX: ffffffffffffffda RBX: 00007ff19f825ff0 RCX: 00007ff19f790799
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000001
RBP: 0000000000000009 R08: 0000000000000000 R09: 00007ff19f825f90
R10: 0000000000000000 R11: 0000000000000246 R12: 00007ffcec9735e0
R13: 00007ff19f825f90 R14: 000055556b7154e8 R15: 00007ffcec9746b0
 </TASK>

Allocated by task 1208:
 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:3245 [inline]
 slab_alloc mm/slub.c:3255 [inline]
 kmem_cache_alloc+0xf7/0x260 mm/slub.c:3260
 __d_alloc+0x2d/0x6a0 fs/dcache.c:1749
 d_alloc fs/dcache.c:1828 [inline]
 d_alloc_parallel+0xe2/0x1370 fs/dcache.c:2584
 __lookup_slow+0x14c/0x410 fs/namei.c:1656
 lookup_one_len+0x19d/0x2d0 fs/namei.c:2726
 incfs_lookup_dentry+0x60/0xb0 fs/incfs/data_mgmt.c:210
 open_or_create_special_dir+0x4f/0x1d0 fs/incfs/vfs.c:475
 incfs_mount_fs+0x42f/0x890 fs/incfs/vfs.c:1884
 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:3034
 path_mount+0x659/0xff0 fs/namespace.c:3364
 do_mount fs/namespace.c:3377 [inline]
 __do_sys_mount fs/namespace.c:3585 [inline]
 __se_sys_mount+0x320/0x390 fs/namespace.c:3562
 __x64_sys_mount+0xbf/0xd0 fs/namespace.c:3562
 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 13:
 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:1728 [inline]
 slab_free_freelist_hook+0xc2/0x190 mm/slub.c:1754
 slab_free mm/slub.c:3526 [inline]
 kmem_cache_free+0x100/0x320 mm/slub.c:3544
 __d_free+0x23/0x30 fs/dcache.c:273
 rcu_do_batch+0x532/0xbe0 kernel/rcu/tree.c:2523
 rcu_core+0x5ee/0xf80 kernel/rcu/tree.c:2763
 rcu_core_si+0x9/0x10 kernel/rcu/tree.c:2776
 handle_softirqs+0x250/0x560 kernel/softirq.c:583
 run_ksoftirqd+0x28/0x40 kernel/softirq.c:959
 smpboot_thread_fn+0x45a/0x8c0 kernel/smpboot.c:164
 kthread+0x411/0x500 kernel/kthread.c:337
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:287

Last potentially related work creation:
 kasan_save_stack+0x3a/0x60 mm/kasan/common.c:38
 __kasan_record_aux_stack+0xd2/0x100 mm/kasan/generic.c:348
 kasan_record_aux_stack_noalloc+0xb/0x10 mm/kasan/generic.c:358
 __call_rcu_common kernel/rcu/tree.c:3011 [inline]
 call_rcu+0x10b/0xf80 kernel/rcu/tree.c:3129
 dentry_free+0xbd/0x150 fs/dcache.c:-1
 __dentry_kill+0x50a/0x650 fs/dcache.c:600
 dentry_kill+0xc0/0x2a0 fs/dcache.c:-1
 dput+0x47/0x90 fs/dcache.c:893
 incfs_free_mount_info+0x60/0x200 fs/incfs/data_mgmt.c:166
 incfs_kill_sb+0x1b8/0x220 fs/incfs/vfs.c:1997
 deactivate_locked_super+0xa0/0x100 fs/super.c:335
 deactivate_super+0xaf/0xe0 fs/super.c:366
 cleanup_mnt+0x45b/0x510 fs/namespace.c:1148
 __cleanup_mnt+0x19/0x20 fs/namespace.c:1155
 task_work_run+0x127/0x190 kernel/task_work.c:188
 exit_task_work include/linux/task_work.h:33 [inline]
 do_exit+0xa9e/0x27e0 kernel/exit.c:889
 do_group_exit+0x141/0x310 kernel/exit.c:1003
 __do_sys_exit_group kernel/exit.c:1014 [inline]
 __se_sys_exit_group kernel/exit.c:1012 [inline]
 __x64_sys_exit_group+0x3f/0x40 kernel/exit.c:1012
 x64_sys_call+0x832/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:232
 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

Second to last potentially related work creation:
 kasan_save_stack+0x3a/0x60 mm/kasan/common.c:38
 __kasan_record_aux_stack+0xd2/0x100 mm/kasan/generic.c:348
 kasan_record_aux_stack_noalloc+0xb/0x10 mm/kasan/generic.c:358
 __call_rcu_common kernel/rcu/tree.c:3011 [inline]
 call_rcu+0x10b/0xf80 kernel/rcu/tree.c:3129
 dentry_free+0xbd/0x150 fs/dcache.c:-1
 __dentry_kill+0x50a/0x650 fs/dcache.c:600
 dentry_kill+0xc0/0x2a0 fs/dcache.c:-1
 dput+0x47/0x90 fs/dcache.c:893
 do_unlinkat+0x34a/0x6d0 fs/namei.c:4359
 __do_sys_unlink fs/namei.c:4404 [inline]
 __se_sys_unlink fs/namei.c:4402 [inline]
 __x64_sys_unlink+0x49/0x50 fs/namei.c:4402
 x64_sys_call+0x878/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:88
 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

The buggy address belongs to the object at ffff888129928770
 which belongs to the cache dentry of size 208
The buggy address is located 0 bytes inside of
 208-byte region [ffff888129928770, ffff888129928840)
The buggy address belongs to the page:
page:ffffea0004a64a00 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x129928
flags: 0x4000000000000200(slab|zone=1)
raw: 4000000000000200 0000000000000000 0000000100000001 ffff8881001c4780
raw: 0000000000000000 00000000000f000f 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 0, migratetype Reclaimable, gfp_mask 0x112cd0(GFP_USER|__GFP_NOWARN|__GFP_NORETRY|__GFP_RECLAIMABLE), pid 632, ts 35212089209, free_ts 34028532441
 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+0x2d3a/0x2dc0 mm/page_alloc.c:4485
 __alloc_pages+0x1a2/0x460 mm/page_alloc.c:5822
 alloc_slab_page mm/slub.c:-1 [inline]
 allocate_slab mm/slub.c:1937 [inline]
 new_slab+0xa1/0x4d0 mm/slub.c:2000
 ___slab_alloc+0x381/0x810 mm/slub.c:3033
 __slab_alloc+0x49/0x90 mm/slub.c:3120
 slab_alloc_node mm/slub.c:3211 [inline]
 slab_alloc mm/slub.c:3255 [inline]
 kmem_cache_alloc+0x138/0x260 mm/slub.c:3260
 __d_alloc+0x2d/0x6a0 fs/dcache.c:1749
 d_alloc fs/dcache.c:1828 [inline]
 d_alloc_parallel+0xe2/0x1370 fs/dcache.c:2584
 __lookup_slow+0x14c/0x410 fs/namei.c:1656
 lookup_one_len+0x19d/0x2d0 fs/namei.c:2726
 start_creating+0x167/0x2f0 fs/debugfs/inode.c:354
 __debugfs_create_file+0x78/0x530 fs/debugfs/inode.c:399
 debugfs_create_file+0x4a/0x60 fs/debugfs/inode.c:461
 bdi_debug_register mm/backing-dev.c:112 [inline]
 bdi_register_va+0x2a9/0x5f0 mm/backing-dev.c:891
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+0xae/0x540 mm/page_alloc.c:3616
 free_the_page mm/page_alloc.c:805 [inline]
 __free_pages+0x6c/0x100 mm/page_alloc.c:5898
 __free_slab+0xe8/0x1e0 mm/slub.c:2025
 free_slab mm/slub.c:2040 [inline]
 discard_slab mm/slub.c:2046 [inline]
 __unfreeze_partials+0x160/0x190 mm/slub.c:2532
 put_cpu_partial+0xc6/0x120 mm/slub.c:2612
 __slab_free+0x1d4/0x290 mm/slub.c:3395
 do_slab_free mm/slub.c:3514 [inline]
 ___cache_free+0x104/0x120 mm/slub.c:3535
 qlink_free+0x4d/0x90 mm/kasan/quarantine.c:157
 qlist_free_all+0x5f/0xb0 mm/kasan/quarantine.c:176
 kasan_quarantine_reduce+0x14a/0x170 mm/kasan/quarantine.c:283
 __kasan_slab_alloc+0x2f/0xf0 mm/kasan/common.c:443
 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:3245 [inline]
 slab_alloc mm/slub.c:3255 [inline]
 __kmalloc+0x120/0x2c0 mm/slub.c:4432
 __kmalloc_node include/linux/slab.h:487 [inline]
 kmalloc_node include/linux/slab.h:642 [inline]
 kvmalloc_node+0x211/0x320 mm/util.c:621
 kvmalloc include/linux/mm.h:862 [inline]
 seq_buf_alloc fs/seq_file.c:38 [inline]
 seq_read_iter+0x1fc/0xd30 fs/seq_file.c:210

Memory state around the buggy address:
 ffff888129928600: fb fb fb fb fc fc fc fc fc fc fc fc fa fb fb fb
 ffff888129928680: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff888129928700: fb fb fb fb fb fb fc fc fc fc fc fc fc fc fa fb
                                                             ^
 ffff888129928780: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff888129928800: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
==================================================================
------------[ cut here ]------------
WARNING: CPU: 0 PID: 835 at fs/dcache.c:769 fast_dput+0x210/0x290 fs/dcache.c:769
Modules linked in:
CPU: 0 PID: 835 Comm: syz-executor Tainted: G    B   W         syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026
RIP: 0010:fast_dput+0x210/0x290 fs/dcache.c:769
Code: e5 f2 ff e9 46 fe ff ff 89 d9 80 e1 07 80 c1 03 38 c1 0f 8c 99 fe ff ff 48 89 df e8 ea e4 f2 ff e9 8c fe ff ff e8 50 b6 b3 ff <0f> 0b e9 0b ff ff ff 89 d9 80 e1 07 80 c1 03 38 c1 0f 8c e4 fe ff
RSP: 0018:ffffc90000aa7b40 EFLAGS: 00010293
RAX: ffffffff81b61090 RBX: ffff888129928770 RCX: ffff88811a262780
RDX: 0000000000000000 RSI: 00000000ffffff80 RDI: 0000000000000001
RBP: ffffc90000aa7b70 R08: 0000000000000003 R09: 0000000000000004
R10: dffffc0000000000 R11: fffff52000154f58 R12: 00000000ffffff80
R13: dffffc0000000000 R14: ffff8881299287c8 R15: 1ffff110253250f9
FS:  0000000000000000(0000) GS:ffff8881f7000000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f5763890000 CR3: 000000013a83a000 CR4: 00000000003506b0
Call Trace:
 <TASK>
 dput+0x26/0x90 fs/dcache.c:880
 incfs_free_mount_info+0x60/0x200 fs/incfs/data_mgmt.c:166
 incfs_kill_sb+0x1b8/0x220 fs/incfs/vfs.c:1997
 deactivate_locked_super+0xa0/0x100 fs/super.c:335
 deactivate_super+0xaf/0xe0 fs/super.c:366
 cleanup_mnt+0x45b/0x510 fs/namespace.c:1148
 __cleanup_mnt+0x19/0x20 fs/namespace.c:1155
 task_work_run+0x127/0x190 kernel/task_work.c:188
 exit_task_work include/linux/task_work.h:33 [inline]
 do_exit+0xa9e/0x27e0 kernel/exit.c:889
 do_group_exit+0x141/0x310 kernel/exit.c:1003
 __do_sys_exit_group kernel/exit.c:1014 [inline]
 __se_sys_exit_group kernel/exit.c:1012 [inline]
 __x64_sys_exit_group+0x3f/0x40 kernel/exit.c:1012
 x64_sys_call+0x832/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:232
 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
RIP: 0033:0x7ff19f790799
Code: Unable to access opcode bytes at RIP 0x7ff19f79076f.
RSP: 002b:00007ffcec972328 EFLAGS: 00000246 ORIG_RAX: 00000000000000e7
RAX: ffffffffffffffda RBX: 00007ff19f825ff0 RCX: 00007ff19f790799
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000001
RBP: 0000000000000009 R08: 0000000000000000 R09: 00007ff19f825f90
R10: 0000000000000000 R11: 0000000000000246 R12: 00007ffcec9735e0
R13: 00007ff19f825f90 R14: 000055556b7154e8 R15: 00007ffcec9746b0
 </TASK>
---[ end trace 7e986cb685b40016 ]---