syzbot


KCSAN: data-race in d_delete / step_into_slowpath

Status: moderation: reported on 2025/12/04 05:22
Subsystems: fs
[Documentation on labels]
Reported-by: syzbot+b33915cb4c9e1c5692ec@syzkaller.appspotmail.com
First crash: 2d07h, last: 13h10m

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

read-write to 0xffff888106e99000 of 4 bytes by task 3306 on cpu 1:
 d_delete+0x15a/0x180 fs/dcache.c:2478
 d_delete_notify+0x32/0x100 include/linux/fsnotify.h:375
 vfs_unlink+0x32c/0x440 fs/namei.c:5384
 do_unlinkat+0x1cd/0x4b0 fs/namei.c:5439
 __do_sys_unlink fs/namei.c:5474 [inline]
 __se_sys_unlink fs/namei.c:5472 [inline]
 __x64_sys_unlink+0x2e/0x40 fs/namei.c:5472
 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+0xd8/0x2a0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff888106e99000 of 4 bytes by task 3004 on cpu 0:
 __d_entry_type include/linux/dcache.h:414 [inline]
 d_is_symlink include/linux/dcache.h:444 [inline]
 step_into_slowpath+0x120/0x480 fs/namei.c:2047
 step_into fs/namei.c:2091 [inline]
 walk_component fs/namei.c:2227 [inline]
 lookup_last fs/namei.c:2722 [inline]
 path_lookupat+0x330/0x500 fs/namei.c:2746
 filename_lookup+0x147/0x340 fs/namei.c:2775
 do_readlinkat+0x7d/0x320 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+0xd8/0x2a0 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: 3004 Comm: udevd Not tainted syzkaller #0 PREEMPT(voluntary) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
==================================================================

Crashes (2):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2025/12/06 00:06 upstream d1d36025a617 d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in d_delete / step_into_slowpath
2025/12/04 05:21 upstream 8f7aa3d3c732 d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in d_delete / step_into_slowpath
* Struck through repros no longer work on HEAD.