syzbot


KCSAN: data-race in __dentry_kill / step_into_slowpath

Status: moderation: reported on 2026/02/02 05:05
Subsystems: fs
[Documentation on labels]
Reported-by: syzbot+45fdcad4024e88c724bf@syzkaller.appspotmail.com
First crash: 7d06h, last: 7d06h

Sample crash report:
==================================================================
BUG: KCSAN: data-race in __dentry_kill / step_into_slowpath

read-write to 0xffff88811a88ff00 of 4 bytes by task 5826 on cpu 1:
 dentry_unlist fs/dcache.c:615 [inline]
 __dentry_kill+0x1e2/0x460 fs/dcache.c:684
 finish_dput+0x2b/0x200 fs/dcache.c:879
 dput+0x52/0x60 fs/dcache.c:928
 end_dirop fs/namei.c:2898 [inline]
 do_unlinkat+0x217/0x4b0 fs/namei.c:5451
 __do_sys_unlink fs/namei.c:5483 [inline]
 __se_sys_unlink fs/namei.c:5481 [inline]
 __x64_sys_unlink+0x2e/0x40 fs/namei.c:5481
 x64_sys_call+0x2f48/0x3000 arch/x86/include/generated/asm/syscalls_64.h:88
 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 0xffff88811a88ff00 of 4 bytes by task 3002 on cpu 0:
 __d_entry_type include/linux/dcache.h:416 [inline]
 d_is_symlink include/linux/dcache.h:446 [inline]
 step_into_slowpath+0x139/0x4c0 fs/namei.c:2055
 step_into fs/namei.c:2099 [inline]
 walk_component fs/namei.c:2235 [inline]
 lookup_last fs/namei.c:2730 [inline]
 path_lookupat+0x330/0x500 fs/namei.c:2754
 filename_lookup+0x190/0x390 fs/namei.c:2783
 do_readlinkat+0x7d/0x340 fs/stat.c:576
 __do_sys_readlink fs/stat.c:613 [inline]
 __se_sys_readlink fs/stat.c:610 [inline]
 __x64_sys_readlink+0x47/0x60 fs/stat.c:610
 x64_sys_call+0x2af1/0x3000 arch/x86/include/generated/asm/syscalls_64.h:90
 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: 0x00300180 -> 0x00004080

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 3002 Comm: udevd Tainted: G        W           syzkaller #0 PREEMPT(voluntary) 
Tainted: [W]=WARN
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
2026/02/02 05:04 upstream 9f2693489ef8 6b8752f2 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in __dentry_kill / step_into_slowpath
* Struck through repros no longer work on HEAD.