KCSAN: data-race in dentry_unlink_inode / step_into_slowpath

Status: moderation: reported C repro on 2025/12/02 06:25
Subsystems: fs
Labels: prio:low
[Documentation on labels]
Reported-by: syzbot+6b0be41ebcb0c7cd64a5@syzkaller.appspotmail.com
First crash: 333d, last: 16h37m
▶ ▼ ✨ AI Jobs (2)
ID Workflow Result Correct Bug Created Started Finished Revision
6587229b assessment-security DenialOfService: ❌ Exploitable: ❌ FilesystemTrigger: ❌ NetworkTrigger: ❌ PeripheralTrigger: ❌ RemoteTrigger: ❌ Unprivileged: ✅ UserNamespace: ✅ VMGuestTrigger: ❌ VMHostTrigger: ❌ ❓ KCSAN: data-race in dentry_unlink_inode / step_into_slowpath 2026/05/24 10:56 2026/05/24 10:56 2026/05/24 11:27 c69befb3
1fd06afa assessment-kcsan Benign: ✅ Confident: ✅ ❓ KCSAN: data-race in dentry_unlink_inode / step_into_slowpath 2026/01/15 12:17 2026/01/15 12:17 2026/01/15 12:20 a9d6a792

Sample crash report:
==================================================================
BUG: KCSAN: data-race in dentry_unlink_inode / step_into_slowpath

write to 0xffff888106ece870 of 8 bytes by task 3663 on cpu 0:
 __d_clear_type_and_inode fs/dcache.c:420 [inline]
 dentry_unlink_inode+0x65/0x260 fs/dcache.c:464
 d_delete+0x164/0x180 fs/dcache.c:2706
 d_delete_notify+0x32/0x100 include/linux/fsnotify.h:379
 vfs_unlink+0x287/0x490 fs/namei.c:5693
 filename_unlinkat+0x1dc/0x410 fs/namei.c:5748
 __do_sys_unlink fs/namei.c:5783 [inline]
 __se_sys_unlink+0x2b/0xe0 fs/namei.c:5780
 __x64_sys_unlink+0x1f/0x30 fs/namei.c:5780
 x64_sys_call+0x18ee/0x2550 arch/x86/include/generated/asm/syscalls_64.h:88
 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
 do_syscall_64+0x112/0x360 arch/x86/entry/syscall_64.c:84
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff888106ece870 of 8 bytes by task 3666 on cpu 1:
 step_into_slowpath+0x127/0x600 fs/namei.c:2134
 step_into fs/namei.c:2181 [inline]
 walk_component fs/namei.c:2317 [inline]
 lookup_last fs/namei.c:2818 [inline]
 path_lookupat+0x2eb/0x4c0 fs/namei.c:2842
 filename_lookup+0x18f/0x390 fs/namei.c:2871
 do_readlinkat+0x74/0x2f0 fs/stat.c:571
 __do_sys_readlink fs/stat.c:605 [inline]
 __se_sys_readlink fs/stat.c:602 [inline]
 __x64_sys_readlink+0x47/0x60 fs/stat.c:602
 x64_sys_call+0x1d41/0x2550 arch/x86/include/generated/asm/syscalls_64.h:90
 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
 do_syscall_64+0x112/0x360 arch/x86/entry/syscall_64.c:84
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0xffff8881004d1948 -> 0x0000000000000000

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 3666 Comm: syz-executor100 Not tainted syzkaller #0 PREEMPT(lazy) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/16/2026
==================================================================
==================================================================
BUG: KCSAN: data-race in __d_instantiate / lookup_fast

read-write to 0xffff888106ed06c0 of 4 bytes by task 3663 on cpu 0:
 fsnotify_update_flags include/linux/fsnotify_backend.h:-1 [inline]
 __d_instantiate+0x2a8/0x390 fs/dcache.c:2160
 d_instantiate_new+0x68/0xf0 fs/dcache.c:2206
 ext4_add_nondir+0x187/0x1b0 fs/ext4/namei.c:2796
 ext4_symlink+0x58f/0x660 fs/ext4/namei.c:3435
 vfs_symlink+0xfd/0x220 fs/namei.c:5823
 filename_symlinkat+0xe8/0x2b0 fs/namei.c:5848
 __do_sys_symlink fs/namei.c:5875 [inline]
 __se_sys_symlink+0x42/0x1b0 fs/namei.c:5871
 __x64_sys_symlink+0x31/0x40 fs/namei.c:5871
 x64_sys_call+0x211f/0x2550 arch/x86/include/generated/asm/syscalls_64.h:89
 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
 do_syscall_64+0x112/0x360 arch/x86/entry/syscall_64.c:84
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff888106ed06c0 of 4 bytes by task 3666 on cpu 1:
 d_revalidate fs/namei.c:1034 [inline]
 lookup_fast+0xf1/0x320 fs/namei.c:1868
 walk_component fs/namei.c:2307 [inline]
 lookup_last fs/namei.c:2818 [inline]
 path_lookupat+0x120/0x4c0 fs/namei.c:2842
 filename_lookup+0x18f/0x390 fs/namei.c:2871
 do_readlinkat+0x74/0x2f0 fs/stat.c:571
 __do_sys_readlink fs/stat.c:605 [inline]
 __se_sys_readlink fs/stat.c:602 [inline]
 __x64_sys_readlink+0x47/0x60 fs/stat.c:602
 x64_sys_call+0x1d41/0x2550 arch/x86/include/generated/asm/syscalls_64.h:90
 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
 do_syscall_64+0x112/0x360 arch/x86/entry/syscall_64.c:84
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x00040040 -> 0x00340040

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 3666 Comm: syz-executor100 Not tainted syzkaller #0 PREEMPT(lazy) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/16/2026
==================================================================
==================================================================
BUG: KCSAN: data-race in dont_mount / step_into_slowpath

read-write to 0xffff888106ed99c0 of 4 bytes by task 3663 on cpu 0:
 dont_mount+0x2a/0x40 include/linux/dcache.h:412
 vfs_unlink+0x202/0x490 fs/namei.c:5680
 filename_unlinkat+0x1dc/0x410 fs/namei.c:5748
 __do_sys_unlink fs/namei.c:5783 [inline]
 __se_sys_unlink+0x2b/0xe0 fs/namei.c:5780
 __x64_sys_unlink+0x1f/0x30 fs/namei.c:5780
 x64_sys_call+0x18ee/0x2550 arch/x86/include/generated/asm/syscalls_64.h:88
 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
 do_syscall_64+0x112/0x360 arch/x86/entry/syscall_64.c:84
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff888106ed99c0 of 4 bytes by task 3666 on cpu 1:
 d_managed include/linux/dcache.h:433 [inline]
 handle_mounts fs/namei.c:1738 [inline]
 step_into_slowpath+0xea/0x600 fs/namei.c:2131
 step_into fs/namei.c:2181 [inline]
 walk_component fs/namei.c:2317 [inline]
 lookup_last fs/namei.c:2818 [inline]
 path_lookupat+0x2eb/0x4c0 fs/namei.c:2842
 filename_lookup+0x18f/0x390 fs/namei.c:2871
 do_readlinkat+0x74/0x2f0 fs/stat.c:571
 __do_sys_readlink fs/stat.c:605 [inline]
 __se_sys_readlink fs/stat.c:602 [inline]
 __x64_sys_readlink+0x47/0x60 fs/stat.c:602
 x64_sys_call+0x1d41/0x2550 arch/x86/include/generated/asm/syscalls_64.h:90
 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
 do_syscall_64+0x112/0x360 arch/x86/entry/syscall_64.c:84
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x00340040 -> 0x00040040

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 3666 Comm: syz-executor100 Not tainted syzkaller #0 PREEMPT(lazy) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/16/2026
==================================================================
==================================================================
BUG: KCSAN: data-race in __d_instantiate / path_lookupat

read-write to 0xffff888105940540 of 4 bytes by task 3663 on cpu 0:
 fsnotify_update_flags include/linux/fsnotify_backend.h:-1 [inline]
 __d_instantiate+0x2a8/0x390 fs/dcache.c:2160
 d_instantiate_new+0x68/0xf0 fs/dcache.c:2206
 ext4_add_nondir+0x187/0x1b0 fs/ext4/namei.c:2796
 ext4_symlink+0x58f/0x660 fs/ext4/namei.c:3435
 vfs_symlink+0xfd/0x220 fs/namei.c:5823
 filename_symlinkat+0xe8/0x2b0 fs/namei.c:5848
 __do_sys_symlink fs/namei.c:5875 [inline]
 __se_sys_symlink+0x42/0x1b0 fs/namei.c:5871
 __x64_sys_symlink+0x31/0x40 fs/namei.c:5871
 x64_sys_call+0x211f/0x2550 arch/x86/include/generated/asm/syscalls_64.h:89
 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
 do_syscall_64+0x112/0x360 arch/x86/entry/syscall_64.c:84
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff888105940540 of 4 bytes by task 3666 on cpu 1:
 d_managed include/linux/dcache.h:433 [inline]
 step_into fs/namei.c:2169 [inline]
 walk_component fs/namei.c:2317 [inline]
 lookup_last fs/namei.c:2818 [inline]
 path_lookupat+0x19b/0x4c0 fs/namei.c:2842
 filename_lookup+0x18f/0x390 fs/namei.c:2871
 do_readlinkat+0x74/0x2f0 fs/stat.c:571
 __do_sys_readlink fs/stat.c:605 [inline]
 __se_sys_readlink fs/stat.c:602 [inline]
 __x64_sys_readlink+0x47/0x60 fs/stat.c:602
 x64_sys_call+0x1d41/0x2550 arch/x86/include/generated/asm/syscalls_64.h:90
 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
 do_syscall_64+0x112/0x360 arch/x86/entry/syscall_64.c:84
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x00040040 -> 0x00340040

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 3666 Comm: syz-executor100 Not tainted syzkaller #0 PREEMPT(lazy) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/16/2026
==================================================================

Crashes (612):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/10/12 02:22 git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git b88c841d1164 4f92358f .config console log report C ci2-upstream-kcsan-gce KCSAN: data-race in dentry_unlink_inode / step_into_slowpath
2026/10/30 17:46 upstream d89e1d186ec9 0ec395f8 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in dentry_unlink_inode / step_into_slowpath
2026/10/30 11:04 upstream d89e1d186ec9 b498adee .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in dentry_unlink_inode / step_into_slowpath
2026/10/29 21:22 upstream 4dd16e31135e b498adee .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in dentry_unlink_inode / step_into_slowpath
2026/10/29 08:20 upstream c339f4010dea b1d00f76 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in dentry_unlink_inode / step_into_slowpath
2026/10/28 12:38 upstream 65ba8f34ec88 858db2ec .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in dentry_unlink_inode / step_into_slowpath
2026/10/27 20:50 upstream 62c457528529 96923c60 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in dentry_unlink_inode / step_into_slowpath
2026/10/27 12:15 upstream d135ab453a74 168cb7a2 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in dentry_unlink_inode / step_into_slowpath
2026/10/26 23:17 upstream 6b4b543fa187 168cb7a2 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in dentry_unlink_inode / step_into_slowpath
2026/10/26 00:12 upstream 21a7f44fd076 1d9ca40b .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in dentry_unlink_inode / step_into_slowpath
2026/10/25 08:31 upstream 6fba331225f5 1d9ca40b .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in dentry_unlink_inode / step_into_slowpath
2026/10/24 12:07 upstream 5b0764a53235 1d9ca40b .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in dentry_unlink_inode / step_into_slowpath
2026/10/24 04:25 upstream 734bef548a96 1d9ca40b .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in dentry_unlink_inode / step_into_slowpath
2026/10/23 04:27 upstream a1c2b1da93f5 d566bfda .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in dentry_unlink_inode / step_into_slowpath
2026/10/22 14:53 upstream 7be4bc52fd9e b55fad29 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in dentry_unlink_inode / step_into_slowpath
2026/10/21 21:43 upstream a804c5742bff 4ba27f85 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in dentry_unlink_inode / step_into_slowpath
2026/10/21 05:23 upstream 4cbdd58dfa7a 61c200c7 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in dentry_unlink_inode / step_into_slowpath
2026/10/20 22:59 upstream f47d223627f8 df8746fb .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in dentry_unlink_inode / step_into_slowpath
2026/10/19 18:37 upstream c03c1a14507d 72cdc28d .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in dentry_unlink_inode / step_into_slowpath
2026/10/19 08:54 upstream c03c1a14507d 432c0077 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in dentry_unlink_inode / step_into_slowpath
2026/10/18 23:33 upstream a0ff06b3a7bd 432c0077 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in dentry_unlink_inode / step_into_slowpath
2026/10/18 07:51 upstream 32c52ec87d62 432c0077 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in dentry_unlink_inode / step_into_slowpath
2026/10/17 17:48 upstream 58161ead29e5 432c0077 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in dentry_unlink_inode / step_into_slowpath
2026/10/17 03:53 upstream 70dd4ee72eb2 432c0077 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in dentry_unlink_inode / step_into_slowpath
2026/10/16 19:14 upstream 2f2f7eeef8b0 4c840a2f .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in dentry_unlink_inode / step_into_slowpath
2026/10/16 09:15 upstream 9aa622dbaab8 3f2522c6 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in dentry_unlink_inode / step_into_slowpath
2026/10/15 02:43 upstream 0fcb05b72344 8fb0ae89 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in dentry_unlink_inode / step_into_slowpath
2026/10/14 21:13 upstream 4056b3c9d3c9 1a71827b .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in dentry_unlink_inode / step_into_slowpath
2026/10/14 11:14 upstream ca3e345926b0 7321cd29 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in dentry_unlink_inode / step_into_slowpath
2026/10/13 07:20 upstream 24a19b953e2a 5a1eeac4 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in dentry_unlink_inode / step_into_slowpath
2026/10/12 16:05 upstream 24a19b953e2a 745a967f .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in dentry_unlink_inode / step_into_slowpath
2026/10/12 05:22 upstream 24a19b953e2a 4f92358f .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in dentry_unlink_inode / step_into_slowpath
2026/10/11 11:23 upstream a5ebb76233b7 4f92358f .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in dentry_unlink_inode / step_into_slowpath
2026/10/10 14:48 upstream 3857c2fe5449 4f92358f .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in dentry_unlink_inode / step_into_slowpath
2026/10/10 08:31 upstream fc1c25014ff8 4f92358f .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in dentry_unlink_inode / step_into_slowpath
2026/10/08 18:06 upstream 6c377d19d4a5 b2734a59 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in dentry_unlink_inode / step_into_slowpath
2026/10/08 06:26 upstream 7b63ef2d55f2 4f6a9fcf .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in dentry_unlink_inode / step_into_slowpath
2026/10/08 00:17 upstream 7b63ef2d55f2 6520ecdb .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in dentry_unlink_inode / step_into_slowpath
2026/10/07 19:38 upstream 602042bf29f6 6520ecdb .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in dentry_unlink_inode / step_into_slowpath
2026/10/06 19:32 upstream 69f80fef3153 f7710056 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in dentry_unlink_inode / step_into_slowpath
2026/10/06 11:38 upstream 2c3418fffa9d f7710056 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in dentry_unlink_inode / step_into_slowpath
2026/10/05 17:29 upstream 67f0943b394d af63e995 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in dentry_unlink_inode / step_into_slowpath
2026/10/05 11:38 upstream a90ee4305c4a af63e995 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in dentry_unlink_inode / step_into_slowpath
2026/10/05 03:55 upstream a90ee4305c4a 57bbd979 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in dentry_unlink_inode / step_into_slowpath
2026/05/24 06:24 upstream 4cbfe4502e3d c69befb3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in dentry_unlink_inode / step_into_slowpath
2026/03/10 13:40 upstream 1f318b96cc84 4683d576 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in dentry_unlink_inode / step_into_slowpath
2026/01/15 00:07 upstream e0d4140e8043 d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in dentry_unlink_inode / step_into_slowpath
2025/12/02 06:25 upstream 1d18101a644e d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in dentry_unlink_inode / step_into_slowpath
* Struck through repros no longer work on HEAD.