KCSAN: data-race in __dentry_kill / lookup_fast (15)

Status: auto-obsoleted due to no activity on 2026/08/05 23:19
Subsystems: fs
Labels: race:benign prio:low
[Documentation on labels]
Reported-by: syzbot+a173cff1ec72cee3d0a2@syzkaller.appspotmail.com
First crash: 195d, last: 58d
▶ ▼ ✨ AI Jobs (2)
ID Workflow Result Correct Bug Created Started Finished Revision
34cf3b4e assessment-security DenialOfService: ❌ Exploitable: ❌ FilesystemTrigger: ❌ NetworkTrigger: ❌ PeripheralTrigger: ❌ RemoteTrigger: ❌ Unprivileged: ✅ UserNamespace: ✅ VMGuestTrigger: ❌ VMHostTrigger: ❌ ❓ KCSAN: data-race in __dentry_kill / lookup_fast (15) 2026/05/23 09:58 2026/05/23 09:58 2026/05/23 10:36 c69befb3
4d95dff6 assessment-kcsan Benign: ✅ Confident: ✅ ✅ KCSAN: data-race in __dentry_kill / lookup_fast (15) 2026/01/25 07:48 2026/01/25 07:48 2026/01/25 07:58 25283130
▶ ▼ Similar bugs (14)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream KCSAN: data-race in __dentry_kill / lookup_fast (5) fs 6 12 1894d 1967d 0/29 auto-closed as invalid on 2021/07/05 09:49
upstream KCSAN: data-race in __dentry_kill / lookup_fast (8) fs 6 8 1206d 1269d 0/29 auto-obsoleted due to no activity on 2023/05/25 00:07
upstream KCSAN: data-race in __dentry_kill / lookup_fast (13) fs 6 5 481d 529d 0/29 auto-obsoleted due to no activity on 2025/06/08 21:40
upstream KCSAN: data-race in __dentry_kill / lookup_fast (2) fs 6 5 2175d 2235d 0/29 auto-closed as invalid on 2020/09/27 09:27
upstream KCSAN: data-race in __dentry_kill / lookup_fast fs 6 10 2258d 2351d 0/29 closed as invalid on 2020/06/18 14:24
upstream KCSAN: data-race in __dentry_kill / lookup_fast (11) fs 6 1 749d 749d 0/29 auto-obsoleted due to no activity on 2024/08/23 20:28
upstream KCSAN: data-race in __dentry_kill / lookup_fast (10) fs 6 3 859d 897d 0/29 auto-obsoleted due to no activity on 2024/05/05 12:07
upstream KCSAN: data-race in __dentry_kill / lookup_fast (12) fs 6 3 585d 638d 0/29 auto-obsoleted due to no activity on 2025/02/24 08:27
upstream KCSAN: data-race in __dentry_kill / lookup_fast (14) fs 6 1 349d 349d 0/29 auto-obsoleted due to no activity on 2025/10/18 05:13
upstream KCSAN: data-race in __dentry_kill / lookup_fast (7) fs 6 27 1316d 1576d 0/29 auto-obsoleted due to no activity on 2023/02/12 11:35
upstream KCSAN: data-race in __dentry_kill / lookup_fast (6) fs 6 1 1722d 1722d 0/29 auto-closed as invalid on 2021/12/25 02:52
upstream KCSAN: data-race in __dentry_kill / lookup_fast (4) fs 6 3 2015d 2040d 0/29 auto-closed as invalid on 2021/03/06 20:57
upstream KCSAN: data-race in __dentry_kill / lookup_fast (3) fs 6 3 2077d 2069d 0/29 auto-closed as invalid on 2021/01/03 16:37
upstream KCSAN: data-race in __dentry_kill / lookup_fast (9) fs 6 31 937d 973d 0/29 auto-obsoleted due to no activity on 2024/02/17 10:11

Sample crash report:
==================================================================
BUG: KCSAN: data-race in __dentry_kill / lookup_fast

read-write to 0xffff888100774600 of 4 bytes by task 3291 on cpu 0:
 dentry_unlist fs/dcache.c:662 [inline]
 __dentry_kill+0x1ed/0x4d0 fs/dcache.c:732
 finish_dput+0x2b/0x200 fs/dcache.c:927
 dput+0x52/0x60 fs/dcache.c:976
 end_dirop fs/namei.c:2952 [inline]
 filename_unlinkat+0x217/0x410 fs/namei.c:5581
 __do_sys_unlink fs/namei.c:5613 [inline]
 __se_sys_unlink+0x2b/0xe0 fs/namei.c:5610
 __x64_sys_unlink+0x1f/0x30 fs/namei.c:5610
 x64_sys_call+0x2eb6/0x3020 arch/x86/include/generated/asm/syscalls_64.h:88
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x12c/0x3b0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff888100774600 of 4 bytes by task 2982 on cpu 1:
 d_revalidate fs/namei.c:1029 [inline]
 lookup_fast+0xf0/0x320 fs/namei.c:1863
 walk_component fs/namei.c:2274 [inline]
 lookup_last fs/namei.c:2785 [inline]
 path_lookupat+0x15c/0x500 fs/namei.c:2809
 filename_lookup+0x190/0x390 fs/namei.c:2838
 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+0x2b51/0x3020 arch/x86/include/generated/asm/syscalls_64.h:90
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x12c/0x3b0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x00300080 -> 0x00004080

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 2982 Comm: udevd Not tainted syzkaller #0 PREEMPT(lazy) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/09/2026
==================================================================

Crashes (15):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/06/10 23:19 upstream acb7500801e9 f79bac11 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in __dentry_kill / lookup_fast
2026/05/31 01:28 upstream 9d87d0fc8c8e 6b4a8443 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in __dentry_kill / lookup_fast
2026/05/01 19:56 upstream 6fe0be6dc7fa 753c55b9 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in __dentry_kill / lookup_fast
2026/04/16 17:04 upstream 1d51b370a0f8 4743f87d .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in __dentry_kill / lookup_fast
2026/04/03 15:55 upstream d8a9a4b11a13 4440e7c2 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in __dentry_kill / lookup_fast
2026/03/22 08:14 upstream 113ae7b4decc 5b92003d .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in __dentry_kill / lookup_fast
2026/03/22 00:54 upstream a0c83177734a 5b92003d .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in __dentry_kill / lookup_fast
2026/03/09 18:51 upstream 1f318b96cc84 176bead5 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in __dentry_kill / lookup_fast
2026/02/17 16:05 upstream 970296997869 06ec4f7b .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in __dentry_kill / lookup_fast
2026/02/12 12:41 upstream c22e26bd0906 76a109e2 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in __dentry_kill / lookup_fast
2026/02/07 01:45 upstream 2687c848e578 f20fc9f9 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in __dentry_kill / lookup_fast
2026/02/01 06:46 upstream ad9a728a3388 6b8752f2 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in __dentry_kill / lookup_fast
2026/01/31 15:26 upstream ad9a728a3388 afc0c4d4 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in __dentry_kill / lookup_fast
2026/01/31 15:26 upstream ad9a728a3388 afc0c4d4 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in __dentry_kill / lookup_fast
2026/01/25 03:23 upstream 5dbeeb268b63 40acda8a .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in __dentry_kill / lookup_fast
* Struck through repros no longer work on HEAD.