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: 51d, last: 6d05h
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 1062d 1105d 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 732d 739d 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 690d 696d 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 809d 778d 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 464d 464d 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 1567d 1778d 0/29 auto-closed as invalid on 2021/11/16 10:39
upstream KCSAN: data-race in drop_nlink / generic_fillattr fs 6 9 1958d 2033d 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 235d 409d 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 1832d 1876d 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 0xffff88811b532c60 of 4 bytes by task 3307 on cpu 1:
 drop_nlink+0x3d/0xa0 fs/inode.c:418
 __simple_unlink fs/libfs.c:792 [inline]
 simple_unlink+0x60/0x80 fs/libfs.c:806
 shmem_unlink+0x12d/0x140 mm/shmem.c:3991
 shmem_rename2+0x18e/0x310 mm/shmem.c:4072
 vfs_rename+0x97f/0xad0 fs/namei.c:5938
 do_renameat2+0x39a/0x850 fs/namei.c:6056
 __do_sys_rename fs/namei.c:6099 [inline]
 __se_sys_rename fs/namei.c:6097 [inline]
 __x64_sys_rename+0x58/0x70 fs/namei.c:6097
 x64_sys_call+0x24e/0x3000 arch/x86/include/generated/asm/syscalls_64.h:83
 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 0xffff88811b532c60 of 4 bytes by task 4862 on cpu 0:
 generic_fillattr+0xfb/0x340 fs/stat.c:91
 shmem_getattr+0x181/0x200 mm/shmem.c:1274
 vfs_getattr_nosec+0x146/0x1e0 fs/stat.c:213
 vfs_getattr fs/stat.c:262 [inline]
 vfs_statx_path fs/stat.c:299 [inline]
 vfs_statx+0x113/0x3b0 fs/stat.c:356
 vfs_fstatat+0x115/0x170 fs/stat.c:375
 __do_sys_newfstatat fs/stat.c:542 [inline]
 __se_sys_newfstatat+0x55/0x3e0 fs/stat.c:536
 __x64_sys_newfstatat+0x55/0x70 fs/stat.c:536
 x64_sys_call+0x111f/0x3000 arch/x86/include/generated/asm/syscalls_64.h:263
 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: 0x00000001 -> 0x00000000

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 4862 Comm: udevd Not tainted syzkaller #0 PREEMPT(voluntary) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
==================================================================

Crashes (4):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
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.