KCSAN: data-race in d_lru_del / dentry_kill

Status: moderation: reported on 2026/06/22 23:47
Subsystems: fs
Labels: race:benign prio:low
[Documentation on labels]
Reported-by: syzbot+f7859f6296c8de068452@syzkaller.appspotmail.com
First crash: 49d, last: 3d09h
✨ AI Jobs (2)
ID Workflow Result Correct Bug Created Started Finished Revision
6d8b3804 assessment-security DenialOfService: ❌ Exploitable: ❌ FilesystemTrigger: ❌ NetworkTrigger: ❌ PeripheralTrigger: ❌ RemoteTrigger: ❌ Unprivileged: ✅ UserNamespace: ✅ VMGuestTrigger: ❌ VMHostTrigger: ❌ KCSAN: data-race in d_lru_del / dentry_kill 2026/06/24 00:44 2026/06/24 00:44 2026/06/24 01:09 e30e5c89
65aeb01b assessment-kcsan Benign: ✅ KCSAN: data-race in d_lru_del / dentry_kill 2026/06/22 23:46 2026/06/22 23:46 2026/06/23 00:09 5a630be6

Sample crash report:
==================================================================
BUG: KCSAN: data-race in d_lru_del / dentry_kill

write to 0xffff88810778af00 of 4 bytes by task 2980 on cpu 1:
 d_lru_del+0x4c/0x100 fs/dcache.c:515
 dentry_kill+0x10a/0x500 fs/dcache.c:821
 finish_dput+0x16/0x1d0 fs/dcache.c:1001
 dput+0x48/0x50 fs/dcache.c:1042
 lookup_fast+0x29f/0x320 fs/namei.c:1886
 walk_component fs/namei.c:2278 [inline]
 lookup_last fs/namei.c:2789 [inline]
 path_lookupat+0x120/0x4c0 fs/namei.c:2813
 filename_lookup+0x18f/0x390 fs/namei.c:2842
 do_readlinkat+0x74/0x2f0 fs/stat.c:571
 __do_sys_readlink fs/stat.c:605 [inline]
 __se_sys_readlink fs/stat.c:602 [inline]
 __x64_sys_readlink+0x47/0x60 fs/stat.c:602
 x64_sys_call+0x2b51/0x3020 arch/x86/include/generated/asm/syscalls_64.h:90
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x136/0x3c0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff88810778af00 of 4 bytes by task 3289 on cpu 0:
 dentry_unlist fs/dcache.c:694 [inline]
 dentry_kill+0x2d3/0x500 fs/dcache.c:840
 finish_dput+0x16/0x1d0 fs/dcache.c:1001
 dput+0x48/0x50 fs/dcache.c:1042
 lookup_fast+0x29f/0x320 fs/namei.c:1886
 walk_component fs/namei.c:2278 [inline]
 link_path_walk+0x523/0xdd0 fs/namei.c:2656
 path_openat+0x1ac/0x2000 fs/namei.c:4859
 do_file_open+0x16c/0x290 fs/namei.c:4892
 do_sys_openat2+0xa0/0x130 fs/open.c:1368
 do_sys_open fs/open.c:1374 [inline]
 __do_sys_openat fs/open.c:1390 [inline]
 __se_sys_openat fs/open.c:1385 [inline]
 __x64_sys_openat+0xf2/0x120 fs/open.c:1385
 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+0x136/0x3c0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x00140004 -> 0x00000004

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 3289 Comm: udevd Not tainted syzkaller #0 PREEMPT(lazy) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
==================================================================

Crashes (3):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/08/08 11:02 upstream bcc44b6785f2 5d63f80b .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in d_lru_del / dentry_kill
2026/07/20 04:56 upstream 82a47586c0b9 72524a66 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in d_lru_del / dentry_kill
2026/06/22 23:46 upstream 1dc18801be29 5a630be6 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in d_lru_del / dentry_kill
* Struck through repros no longer work on HEAD.