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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: 22h52m, last: 22h52m
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 1700d 1773d 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 1012d 1075d 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 287d 335d 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 1981d 2041d 0/29 auto-closed as invalid on 2020/09/27 09:27
upstream KCSAN: data-race in __dentry_kill / lookup_fast fs 6 10 2064d 2157d 0/29 closed as invalid on 2020/06/18 14:24
upstream KCSAN: data-race in __dentry_kill / lookup_fast (11) fs 6 1 555d 555d 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 665d 703d 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 391d 444d 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 155d 155d 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 1122d 1382d 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 1527d 1527d 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 1821d 1846d 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 1883d 1875d 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 743d 779d 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 0xffff8881004980c0 of 4 bytes by task 3313 on cpu 0:
 dentry_unlist fs/dcache.c:615 [inline]
 __dentry_kill+0x230/0x4b0 fs/dcache.c:684
 finish_dput+0x2b/0x200 fs/dcache.c:879
 dput+0x52/0x60 fs/dcache.c:928
 __fput+0x444/0x650 fs/file_table.c:476
 fput_close_sync+0xad/0x190 fs/file_table.c:573
 __do_sys_close fs/open.c:1573 [inline]
 __se_sys_close fs/open.c:1558 [inline]
 __x64_sys_close+0x55/0xf0 fs/open.c:1558
 x64_sys_call+0x2c25/0x3000 arch/x86/include/generated/asm/syscalls_64.h:4
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xc0/0x2a0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff8881004980c0 of 4 bytes by task 4860 on cpu 1:
 d_revalidate fs/namei.c:976 [inline]
 lookup_fast+0xf0/0x320 fs/namei.c:1814
 lookup_fast_for_open fs/namei.c:4486 [inline]
 open_last_lookups fs/namei.c:4520 [inline]
 path_openat+0x415/0x23c0 fs/namei.c:4793
 do_filp_open+0x15d/0x280 fs/namei.c:4823
 do_sys_openat2+0xa6/0x150 fs/open.c:1430
 do_sys_open fs/open.c:1436 [inline]
 __do_sys_openat fs/open.c:1452 [inline]
 __se_sys_openat fs/open.c:1447 [inline]
 __x64_sys_openat+0xf2/0x120 fs/open.c:1447
 x64_sys_call+0x2b07/0x3000 arch/x86/include/generated/asm/syscalls_64.h:258
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xc0/0x2a0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x00200080 -> 0x00004080

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 4860 Comm: syz-executor Not tainted syzkaller #0 PREEMPT(voluntary) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
==================================================================

Crashes (1):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
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.