syzbot


KCSAN: data-race in dentry_unlink_inode / path_openat

Status: moderation: reported on 2025/12/19 00:48
Subsystems: fs
[Documentation on labels]
Reported-by: syzbot+f8e6c6d437af7e678fd0@syzkaller.appspotmail.com
First crash: 1d13h, last: 1d13h

Sample crash report:
==================================================================
BUG: KCSAN: data-race in dentry_unlink_inode / path_openat

write to 0xffff88811b1944b0 of 8 bytes by task 3530 on cpu 0:
 __d_clear_type_and_inode fs/dcache.c:420 [inline]
 dentry_unlink_inode+0x65/0x260 fs/dcache.c:457
 __dentry_kill+0x18d/0x4b0 fs/dcache.c:670
 finish_dput+0x2b/0x200 fs/dcache.c:879
 dput+0x52/0x60 fs/dcache.c:928
 end_renaming fs/namei.c:4052 [inline]
 do_renameat2+0x44a/0x810 fs/namei.c:6049
 __do_sys_rename fs/namei.c:6090 [inline]
 __se_sys_rename fs/namei.c:6088 [inline]
 __x64_sys_rename+0x58/0x70 fs/namei.c:6088
 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+0xd8/0x2c0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff88811b1944b0 of 8 bytes by task 3008 on cpu 1:
 step_into fs/namei.c:2080 [inline]
 open_last_lookups fs/namei.c:4575 [inline]
 path_openat+0x677/0x23b0 fs/namei.c:4784
 do_filp_open+0x109/0x230 fs/namei.c:4814
 do_sys_openat2+0xa6/0x150 fs/open.c:1430
 do_sys_open fs/open.c:1436 [inline]
 __do_sys_openat fs/open.c:1452 [inline]
 __se_sys_openat fs/open.c:1447 [inline]
 __x64_sys_openat+0xf2/0x120 fs/open.c:1447
 x64_sys_call+0x2b07/0x3000 arch/x86/include/generated/asm/syscalls_64.h:258
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xd8/0x2c0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0xffff88812162f7b8 -> 0x0000000000000000

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 3008 Comm: udevd Not tainted syzkaller #0 PREEMPT(voluntary) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
==================================================================

Crashes (1):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2025/12/19 00:48 upstream 516471569089 d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in dentry_unlink_inode / path_openat
* Struck through repros no longer work on HEAD.