KCSAN: data-race in drop_nlink / generic_fillattr (11)

Status: moderation: reported on 2026/08/01 12:00
Subsystems: fs
Labels: race:benign prio:low
[Documentation on labels]
Reported-by: syzbot+5ed997d7a0e87b2edabb@syzkaller.appspotmail.com
First crash: 4d11h, last: 4d11h
✨ AI Jobs (2)
ID Workflow Result Correct Bug Created Started Finished Revision
95bf59e0 assessment-security DenialOfService: ❌ Exploitable: ❌ FilesystemTrigger: ❌ NetworkTrigger: ❌ PeripheralTrigger: ❌ RemoteTrigger: ❌ Unprivileged: ✅ UserNamespace: ✅ VMGuestTrigger: ❌ VMHostTrigger: ❌ KCSAN: data-race in drop_nlink / generic_fillattr (11) 2026/08/03 00:54 2026/08/03 00:54 2026/08/03 01:24 e611ffe1
69ab6050 assessment-kcsan Benign: ✅ KCSAN: data-race in drop_nlink / generic_fillattr (11) 2026/08/01 11:59 2026/08/01 11:59 2026/08/01 12:30 e611ffe1
Similar bugs (10)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream KCSAN: data-race in drop_nlink / generic_fillattr (4) fs 6 2 1253d 1296d 0/29 auto-obsoleted due to no activity on 2023/04/11 17:00
upstream KCSAN: data-race in drop_nlink / generic_fillattr (6) fs 6 2 923d 929d 0/29 auto-obsoleted due to no activity on 2024/02/29 22:16
upstream KCSAN: data-race in drop_nlink / generic_fillattr (7) fs 6 2 881d 887d 0/29 auto-obsoleted due to no activity on 2024/04/11 18:19
upstream KCSAN: data-race in drop_nlink / generic_fillattr (5) fs 6 2 1000d 968d 0/29 auto-obsoleted due to no activity on 2023/12/25 00:01
upstream KCSAN: data-race in drop_nlink / generic_fillattr (10) fs prio:low 6 11 114d 242d 0/29 auto-obsoleted due to no activity on 2026/06/08 00:09
upstream KCSAN: data-race in drop_nlink / generic_fillattr (8) fs 6 1 655d 655d 0/29 auto-obsoleted due to no activity on 2024/11/23 13:06
upstream KCSAN: data-race in drop_nlink / generic_fillattr (3) fs 6 22 1758d 1969d 0/29 auto-closed as invalid on 2021/11/16 10:39
upstream KCSAN: data-race in drop_nlink / generic_fillattr fs 6 9 2148d 2224d 0/29 auto-closed as invalid on 2020/10/22 03:32
upstream KCSAN: data-race in drop_nlink / generic_fillattr (9) fs 6 7 425d 600d 0/29 auto-obsoleted due to no activity on 2025/08/01 02:38
upstream KCSAN: data-race in drop_nlink / generic_fillattr (2) fs 6 8 2022d 2067d 0/29 auto-closed as invalid on 2021/02/25 00:13

Sample crash report:
==================================================================
BUG: KCSAN: data-race in drop_nlink / generic_fillattr

write to 0xffff88818ce46f00 of 4 bytes by task 32681 on cpu 0:
 drop_nlink+0x3d/0xa0 fs/inode.c:409
 __simple_unlink fs/libfs.c:793 [inline]
 simple_unlink+0x60/0x80 fs/libfs.c:807
 shmem_unlink+0x12d/0x140 mm/shmem.c:3927
 shmem_rename2+0x185/0x310 mm/shmem.c:4008
 vfs_rename+0x963/0xac0 fs/namei.c:6074
 filename_renameat2+0x3a4/0x6a0 fs/namei.c:6192
 __do_sys_rename fs/namei.c:6236 [inline]
 __se_sys_rename+0x4a/0x1c0 fs/namei.c:6232
 __x64_sys_rename+0x31/0x40 fs/namei.c:6232
 x64_sys_call+0x2b3/0x3020 arch/x86/include/generated/asm/syscalls_64.h:83
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x136/0x3c0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff88818ce46f00 of 4 bytes by task 24648 on cpu 1:
 generic_fillattr+0xfc/0x340 fs/stat.c:91
 shmem_getattr+0x181/0x200 mm/shmem.c:1312
 vfs_getattr_nosec+0x146/0x1e0 fs/stat.c:213
 vfs_getattr fs/stat.c:262 [inline]
 vfs_fstat fs/stat.c:281 [inline]
 __do_sys_newfstat fs/stat.c:551 [inline]
 __se_sys_newfstat+0x96/0x460 fs/stat.c:546
 __x64_sys_newfstat+0x31/0x40 fs/stat.c:546
 x64_sys_call+0x2773/0x3020 arch/x86/include/generated/asm/syscalls_64.h:6
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x136/0x3c0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x00000001 -> 0x00000000

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 24648 Comm: udevd Tainted: G        W           syzkaller #0 PREEMPT(lazy) 
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
==================================================================
udevd[24648]: inotify_add_watch(7, /dev/loop9p23, 10) failed: No such file or directory

Crashes (1):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/08/01 11:59 upstream 0131b508c0e2 e611ffe1 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in drop_nlink / generic_fillattr
* Struck through repros no longer work on HEAD.