syzbot


KCSAN: data-race in fill_mg_cmtime / simple_rename_timestamp (5)

Status: moderation: reported on 2026/04/29 08:30
Subsystems: fs
[Documentation on labels]
Reported-by: syzbot+7063dc5c0c5911eff5c6@syzkaller.appspotmail.com
First crash: 14h54m, last: 14h54m
✨ AI Jobs (1)
ID Workflow Result Correct Bug Created Started Finished Revision Error
25398232-5323-48e0-9b06-ac204c662f1b assessment-kcsan Benign: ✅  Confident: ✅  KCSAN: data-race in fill_mg_cmtime / simple_rename_timestamp (5) 2026/04/29 08:30 2026/04/29 08:30 2026/04/29 08:50 95008c030835c4879528388a94859e825cd16d84
Similar bugs (4)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream KCSAN: data-race in fill_mg_cmtime / simple_rename_timestamp (3) fs 6 1 213d 213d 0/29 auto-obsoleted due to no activity on 2025/11/23 12:31
upstream KCSAN: data-race in fill_mg_cmtime / simple_rename_timestamp fs 6 3 464d 488d 0/29 auto-obsoleted due to no activity on 2025/03/17 15:26
upstream KCSAN: data-race in fill_mg_cmtime / simple_rename_timestamp (2) fs 6 3 326d 401d 0/29 auto-obsoleted due to no activity on 2025/08/02 01:00
upstream KCSAN: data-race in fill_mg_cmtime / simple_rename_timestamp (4) fs 6 1 79d 79d 0/29 auto-obsoleted due to no activity on 2026/04/06 10:30

Sample crash report:
==================================================================
BUG: KCSAN: data-race in fill_mg_cmtime / simple_rename_timestamp

write to 0xffff8881043f714c of 4 bytes by task 3285 on cpu 1:
 inode_set_mtime_to_ts include/linux/fs.h:1660 [inline]
 simple_rename_timestamp+0x53/0xd0 fs/libfs.c:840
 shmem_rename2+0x2df/0x310 mm/shmem.c:4074
 vfs_rename+0x97f/0xad0 fs/namei.c:6054
 filename_renameat2+0x3b6/0x6e0 fs/namei.c:6172
 __do_sys_rename fs/namei.c:6216 [inline]
 __se_sys_rename+0x4a/0x1c0 fs/namei.c:6212
 __x64_sys_rename+0x31/0x40 fs/namei.c:6212
 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/0x3b0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff8881043f714c of 4 bytes by task 3890 on cpu 0:
 inode_get_mtime_nsec include/linux/fs.h:1646 [inline]
 inode_get_mtime include/linux/fs.h:1652 [inline]
 fill_mg_cmtime+0x5b/0x240 fs/stat.c:55
 generic_fillattr+0x24a/0x340 fs/stat.c:99
 shmem_getattr+0x181/0x200 mm/shmem.c:1302
 vfs_getattr_nosec+0x146/0x1e0 fs/stat.c:213
 vfs_getattr+0x48/0x60 fs/stat.c:262
 vfs_statx_path+0x28/0x140 fs/stat.c:299
 vfs_statx+0xc4/0x170 fs/stat.c:356
 vfs_fstatat+0x118/0x170 fs/stat.c:373
 __do_sys_newfstatat fs/stat.c:538 [inline]
 __se_sys_newfstatat+0x55/0x3e0 fs/stat.c:532
 __x64_sys_newfstatat+0x55/0x70 fs/stat.c:532
 x64_sys_call+0x2c64/0x3020 arch/x86/include/generated/asm/syscalls_64.h:263
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x12c/0x3b0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x02fd159a -> 0x036ca54d

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 3890 Comm: udevd Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/18/2026
==================================================================

Crashes (1):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/04/29 08:30 upstream dca922e019dd 7ca9e4d8 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in fill_mg_cmtime / simple_rename_timestamp
* Struck through repros no longer work on HEAD.