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KCSAN: data-race in generic_fillattr / shmem_symlink (5)

Status: moderation: reported on 2025/10/13 22:26
Subsystems: mm
[Documentation on labels]
Reported-by: syzbot+2d0e5d2b4dbae91dc4fe@syzkaller.appspotmail.com
First crash: 47d, last: 19d
Similar bugs (4)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream KCSAN: data-race in generic_fillattr / shmem_symlink (2) mm 6 247 584d 723d 0/29 auto-obsoleted due to no activity on 2024/05/30 03:00
upstream KCSAN: data-race in generic_fillattr / shmem_symlink (3) mm 6 16 414d 520d 0/29 auto-obsoleted due to no activity on 2024/11/16 05:24
upstream KCSAN: data-race in generic_fillattr / shmem_symlink (4) mm 6 6 254d 355d 0/29 auto-obsoleted due to no activity on 2025/05/15 12:20
upstream KCSAN: data-race in generic_fillattr / shmem_symlink fs 6 30 1995d 2185d 0/29 closed as invalid on 2020/06/18 14:24

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

write to 0xffff88810324d54c of 4 bytes by task 3635 on cpu 1:
 inode_set_mtime_to_ts include/linux/fs.h:1839 [inline]
 shmem_symlink+0x387/0x3d0 mm/shmem.c:4131
 vfs_symlink+0xd4/0x1e0 fs/namei.c:4817
 do_symlinkat+0xc7/0x3c0 fs/namei.c:4843
 __do_sys_symlink fs/namei.c:4864 [inline]
 __se_sys_symlink fs/namei.c:4862 [inline]
 __x64_sys_symlink+0x50/0x60 fs/namei.c:4862
 x64_sys_call+0x23d0/0x3000 arch/x86/include/generated/asm/syscalls_64.h:89
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xd2/0x200 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff88810324d54c of 4 bytes by task 3544 on cpu 0:
 inode_get_mtime_nsec include/linux/fs.h:1825 [inline]
 inode_get_mtime include/linux/fs.h:1831 [inline]
 generic_fillattr+0x20e/0x340 fs/stat.c:102
 shmem_getattr+0x181/0x200 mm/shmem.c:1257
 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+0x113/0x390 fs/stat.c:356
 vfs_fstatat+0x115/0x170 fs/stat.c:375
 __do_sys_newfstatat fs/stat.c:542 [inline]
 __se_sys_newfstatat+0x55/0x260 fs/stat.c:536
 __x64_sys_newfstatat+0x55/0x70 fs/stat.c:536
 x64_sys_call+0x135a/0x3000 arch/x86/include/generated/asm/syscalls_64.h:263
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xd2/0x200 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x0790a785 -> 0x0788d7e7

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 3544 Comm: udevd Not tainted syzkaller #0 PREEMPT(voluntary) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/02/2025
==================================================================

Crashes (2):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2025/11/10 20:05 upstream 4ea7c1717f3f 4e1406b4 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in generic_fillattr / shmem_symlink
2025/10/13 22:26 upstream 3a8660878839 b6605ba8 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in generic_fillattr / shmem_symlink
* Struck through repros no longer work on HEAD.