syzbot


KCSAN: data-race in fill_mg_cmtime / inode_set_ctime_current (2)

Status: moderation: reported on 2026/01/26 11:47
Subsystems: fs
[Documentation on labels]
Reported-by: syzbot+6da2951b1409c3ab0d6f@syzkaller.appspotmail.com
First crash: 69d, last: 1d23h
✨ AI Jobs (2)
ID Workflow Result Correct Bug Created Started Finished Revision Error
36bbe25f-d1ae-4efb-9b19-bc9e2b62dfa9 repro KCSAN: data-race in fill_mg_cmtime / inode_set_ctime_current (2) 2026/03/08 14:09 2026/03/08 14:09 2026/03/08 14:16 31e9c887f7dc24e04b3ca70d0d54fc34141844b0
a5ba41ad-d030-416f-8c90-39f924d83fc6 assessment-kcsan Benign: ✅  Confident: ✅  KCSAN: data-race in fill_mg_cmtime / inode_set_ctime_current (2) 2026/01/26 23:20 2026/01/26 23:20 2026/01/26 23:22 efb3e894dd7e30475c92970989c58e5aad3d5e7b
Similar bugs (1)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream KCSAN: data-race in fill_mg_cmtime / inode_set_ctime_current fs 6 2 138d 163d 0/29 auto-obsoleted due to no activity on 2026/01/14 01:59

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

write to 0xffff888103fcbb08 of 8 bytes by task 3636 on cpu 1:
 inode_set_ctime_current+0x5f2/0x960 fs/inode.c:2874
 shmem_mknod+0x127/0x170 mm/shmem.c:3902
 shmem_create+0x34/0x50 mm/shmem.c:3957
 lookup_open fs/namei.c:4489 [inline]
 open_last_lookups fs/namei.c:4589 [inline]
 path_openat+0xd75/0x2050 fs/namei.c:4833
 do_file_open+0x16c/0x290 fs/namei.c:4865
 do_sys_openat2+0x94/0x130 fs/open.c:1366
 do_sys_open fs/open.c:1372 [inline]
 __do_sys_openat fs/open.c:1388 [inline]
 __se_sys_openat fs/open.c:1383 [inline]
 __x64_sys_openat+0xf2/0x120 fs/open.c:1383
 x64_sys_call+0x1e39/0x3020 arch/x86/include/generated/asm/syscalls_64.h:258
 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 0xffff888103fcbb08 of 8 bytes by task 6999 on cpu 0:
 fill_mg_cmtime+0x86/0x270 fs/stat.c:56
 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/0x370 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x0000000069d30bdd -> 0x0000000069d30bde

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 6999 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 (3):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/04/04 10:46 upstream 631919fb12fe 4440e7c2 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in fill_mg_cmtime / inode_set_ctime_current
2026/02/23 10:07 upstream 6de23f81a5e0 6beca497 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in fill_mg_cmtime / inode_set_ctime_current
2026/01/26 11:46 upstream 63804fed149a a4c52dd6 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in fill_mg_cmtime / inode_set_ctime_current
* Struck through repros no longer work on HEAD.