syzbot


KCSAN: data-race in drop_nlink / generic_fillattr (10)

Status: moderation: reported on 2025/12/06 20:26
Subsystems: fs
[Documentation on labels]
Reported-by: syzbot+d8fcddf719a374bbc9f2@syzkaller.appspotmail.com
First crash: 96d, last: 2d20h
✨ AI Jobs (1)
ID Workflow Result Correct Bug Created Started Finished Revision Error
55efe54c-df9f-414d-98a3-0c3c552398b6 assessment-kcsan Benign: ✅  Confident: ✅  KCSAN: data-race in drop_nlink / generic_fillattr (10) 2026/01/14 21:54 2026/01/14 21:54 2026/01/14 22:16 a9d6a79219801d2130df3b1a792c57f0e5428e9f
Similar bugs (9)
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 1107d 1150d 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 777d 784d 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 735d 741d 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 854d 823d 0/29 auto-obsoleted due to no activity on 2023/12/25 00:01
upstream KCSAN: data-race in drop_nlink / generic_fillattr (8) fs 6 1 509d 509d 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 1612d 1823d 0/29 auto-closed as invalid on 2021/11/16 10:39
upstream KCSAN: data-race in drop_nlink / generic_fillattr fs 6 9 2003d 2078d 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 280d 454d 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 1877d 1921d 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 0xffff88811de8ef48 of 4 bytes by task 4965 on cpu 0:
 drop_nlink+0x3d/0xa0 fs/inode.c:419
 __simple_unlink fs/libfs.c:794 [inline]
 simple_unlink+0x60/0x80 fs/libfs.c:808
 shmem_unlink+0x12d/0x140 mm/shmem.c:4005
 shmem_rename2+0x18e/0x310 mm/shmem.c:4086
 vfs_rename+0x97f/0xad0 fs/namei.c:6026
 filename_renameat2+0x3b6/0x6e0 fs/namei.c:6144
 __do_sys_rename fs/namei.c:6188 [inline]
 __se_sys_rename+0x4a/0x1c0 fs/namei.c:6184
 __x64_sys_rename+0x31/0x40 fs/namei.c:6184
 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+0x12c/0x370 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff88811de8ef48 of 4 bytes by task 3302 on cpu 1:
 generic_fillattr+0xfb/0x340 fs/stat.c:91
 shmem_getattr+0x181/0x200 mm/shmem.c:1302
 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+0x12c/0x370 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: 3302 Comm: udevd 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 (9):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/03/10 10:11 upstream 1f318b96cc84 6972f302 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in drop_nlink / generic_fillattr
2026/02/22 04:00 upstream fa5c82f4d2bb 6e7b5511 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in drop_nlink / generic_fillattr
2026/02/18 05:51 upstream 2961f841b025 39751c21 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in drop_nlink / generic_fillattr
2026/02/09 11:46 upstream 05f7e89ab973 df949cd9 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in drop_nlink / generic_fillattr
2026/02/08 19:15 upstream e98f34af6116 4c131dc4 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in drop_nlink / generic_fillattr
2026/01/20 23:31 upstream c03e9c42ae8f 06648d9c .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in drop_nlink / generic_fillattr
2026/01/16 14:24 upstream 983d014aafb1 d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in drop_nlink / generic_fillattr
2025/12/21 23:50 upstream 765b233a9b94 d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in drop_nlink / generic_fillattr
2025/12/06 20:26 upstream 416f99c3b16f d6526ea3 .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.