syzbot


KCSAN: data-race in __dentry_kill / step_into (9)

Status: moderation: reported on 2025/05/03 22:30
Subsystems: fs
[Documentation on labels]
Reported-by: syzbot+03eeb7a335f7bec13d0c@syzkaller.appspotmail.com
First crash: 140d, last: 4d16h
Similar bugs (8)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream KCSAN: data-race in __dentry_kill / step_into (6) fs 6 1 522d 522d 0/29 auto-obsoleted due to no activity on 2024/05/21 11:40
upstream KCSAN: data-race in __dentry_kill / step_into (8) fs 6 23 212d 446d 0/29 auto-obsoleted due to no activity on 2025/04/17 06:32
upstream KCSAN: data-race in __dentry_kill / step_into fs 6 1 1807d 1807d 0/29 auto-closed as invalid on 2020/11/14 02:21
upstream KCSAN: data-race in __dentry_kill / step_into (5) fs 6 106 568d 653d 0/29 auto-obsoleted due to no activity on 2024/04/05 18:21
upstream KCSAN: data-race in __dentry_kill / step_into (4) fs 6 1 1302d 1302d 0/29 auto-closed as invalid on 2022/04/03 02:19
upstream KCSAN: data-race in __dentry_kill / step_into (7) fs 6 2 483d 487d 0/29 auto-obsoleted due to no activity on 2024/06/29 19:22
upstream KCSAN: data-race in __dentry_kill / step_into (2) fs 6 3 1562d 1600d 0/29 auto-closed as invalid on 2021/07/16 10:59
upstream KCSAN: data-race in __dentry_kill / step_into (3) fs 6 5 1364d 1422d 0/29 auto-closed as invalid on 2022/01/30 10:25

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

read-write to 0xffff888100446480 of 4 bytes by task 3544 on cpu 0:
 dentry_unlist fs/dcache.c:614 [inline]
 __dentry_kill+0x230/0x4b0 fs/dcache.c:683
 dput+0x5e/0xd0 fs/dcache.c:911
 do_unlinkat+0x259/0x480 fs/namei.c:4653
 __do_sys_unlink fs/namei.c:4696 [inline]
 __se_sys_unlink fs/namei.c:4694 [inline]
 __x64_sys_unlink+0x2e/0x40 fs/namei.c:4694
 x64_sys_call+0x2dc0/0x2ff0 arch/x86/include/generated/asm/syscalls_64.h:88
 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 0xffff888100446480 of 4 bytes by task 2995 on cpu 1:
 __d_entry_type include/linux/dcache.h:411 [inline]
 d_is_symlink include/linux/dcache.h:441 [inline]
 step_into+0x12f/0x820 fs/namei.c:1972
 walk_component+0x162/0x220 fs/namei.c:2135
 lookup_last fs/namei.c:2630 [inline]
 path_lookupat+0xfe/0x2a0 fs/namei.c:2654
 filename_lookup+0x147/0x340 fs/namei.c:2683
 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+0x28da/0x2ff0 arch/x86/include/generated/asm/syscalls_64.h:90
 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: 0x00300080 -> 0x00004080

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 2995 Comm: udevd Not tainted syzkaller #0 PREEMPT(voluntary) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/18/2025
==================================================================

Crashes (7):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2025/09/16 11:43 upstream 46a51f4f5eda e2beed91 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in __dentry_kill / step_into
2025/08/17 03:03 upstream 90d970cade8e 1804e95e .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in __dentry_kill / step_into
2025/07/20 00:54 upstream bf61759db409 7117feec .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in __dentry_kill / step_into
2025/07/04 17:06 upstream 4c06e63b9203 d869b261 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in __dentry_kill / step_into
2025/05/28 15:03 upstream feacb1774bd5 874a1386 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in __dentry_kill / step_into
2025/05/15 05:48 upstream c94d59a126cb d6b2ee52 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in __dentry_kill / step_into
2025/05/03 22:29 upstream 2a239ffbebb5 b0714e37 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in __dentry_kill / step_into
* Struck through repros no longer work on HEAD.