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

Status: moderation: reported on 2026/01/25 03:24
Subsystems: fs
Labels: race:benign
[Documentation on labels]
Reported-by: syzbot+a173cff1ec72cee3d0a2@syzkaller.appspotmail.com
First crash: 46d, last: 3d02h
▶ ▼ ✨ AI Jobs (1)
ID Workflow Result Correct Bug Created Started Finished Revision Error
4d95dff6-caac-4d4a-be77-d7e0d64dd6d5 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 252831309f92afe40cc8f6407200c6b12176b8f4
▶ ▼ 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 1746d 1818d 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 1057d 1121d 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 332d 381d 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 2027d 2087d 0/29 auto-closed as invalid on 2020/09/27 09:27
upstream KCSAN: data-race in __dentry_kill / lookup_fast fs 6 10 2109d 2203d 0/29 closed as invalid on 2020/06/18 14:24
upstream KCSAN: data-race in __dentry_kill / lookup_fast (11) fs 6 1 601d 601d 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 711d 749d 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 437d 490d 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 201d 201d 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 1168d 1428d 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 1573d 1573d 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 1867d 1892d 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 1929d 1921d 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 789d 824d 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

write to 0xffff88811bf98900 of 4 bytes by task 24593 on cpu 0:
 d_lru_del fs/dcache.c:504 [inline]
 __dentry_kill+0xa8/0x460 fs/dcache.c:665
 finish_dput+0x2b/0x200 fs/dcache.c:879
 dput+0x52/0x60 fs/dcache.c:928
 lookup_dcache fs/namei.c:1769 [inline]
 lookup_one_qstr_excl+0x233/0x250 fs/namei.c:1792
 __start_dirop fs/namei.c:2925 [inline]
 start_dirop fs/namei.c:2934 [inline]
 filename_create+0x155/0x220 fs/namei.c:4922
 filename_mknodat+0x13e/0x450 fs/namei.c:5130
 __do_sys_mknodat fs/namei.c:5173 [inline]
 __se_sys_mknodat+0x38/0xf0 fs/namei.c:5169
 __x64_sys_mknodat+0x55/0x70 fs/namei.c:5169
 x64_sys_call+0x312/0x3020 arch/x86/include/generated/asm/syscalls_64.h:260
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x12c/0x370 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff88811bf98900 of 4 bytes by task 24609 on cpu 1:
 d_revalidate fs/namei.c:1029 [inline]
 lookup_fast+0xf0/0x320 fs/namei.c:1864
 lookup_fast_for_open fs/namei.c:4520 [inline]
 open_last_lookups fs/namei.c:4554 [inline]
 path_openat+0x436/0x2050 fs/namei.c:4827
 do_file_open+0x16c/0x290 fs/namei.c:4859
 do_sys_openat2+0x94/0x130 fs/open.c:1366
 do_sys_open fs/open.c:1372 [inline]
 __do_sys_openat fs/open.c:1388 [inline]
 __se_sys_openat fs/open.c:1383 [inline]
 __x64_sys_openat+0xf2/0x120 fs/open.c:1383
 x64_sys_call+0x1e39/0x3020 arch/x86/include/generated/asm/syscalls_64.h:258
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x12c/0x370 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x00040007 -> 0x00004007

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 24609 Comm: syz.2.6296 Tainted: G        W           syzkaller #0 PREEMPT(full) 
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026
==================================================================

Crashes (8):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
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.