syzbot


KCSAN: data-race in __dentry_kill / d_make_discardable

Status: moderation: reported on 2026/01/04 16:39
Subsystems: fs
[Documentation on labels]
Reported-by: syzbot+dc4a60eb3b0f9477a856@syzkaller.appspotmail.com
First crash: 55d, last: 1d06h
✨ AI Jobs (1)
ID Workflow Result Correct Bug Created Started Finished Revision Error
9fdc541a-f419-4e98-ba7c-4f97a1eff072 assessment-kcsan Benign: ✅  Confident: ✅  KCSAN: data-race in __dentry_kill / d_make_discardable 2026/01/14 19:38 2026/01/14 19:38 2026/01/14 19:42 a9d6a79219801d2130df3b1a792c57f0e5428e9f

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

write to 0xffff888107b73cc0 of 4 bytes by task 3303 on cpu 0:
 d_make_discardable+0x4f/0xa0 fs/dcache.c:936
 simple_unlink+0x68/0x80 fs/libfs.c:809
 shmem_unlink+0x12d/0x140 mm/shmem.c:4005
 shmem_rename2+0x18e/0x310 mm/shmem.c:4086
 vfs_rename+0x97f/0xad0 fs/namei.c:6026
 filename_renameat2+0x3b6/0x6e0 fs/namei.c:6144
 __do_sys_rename fs/namei.c:6188 [inline]
 __se_sys_rename+0x4a/0x1c0 fs/namei.c:6184
 __x64_sys_rename+0x31/0x40 fs/namei.c:6184
 x64_sys_call+0x2b3/0x3020 arch/x86/include/generated/asm/syscalls_64.h:83
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x12c/0x370 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff888107b73cc0 of 4 bytes by task 3718 on cpu 1:
 dentry_unlist fs/dcache.c:640 [inline]
 __dentry_kill+0x25c/0x460 fs/dcache.c:684
 finish_dput+0x2b/0x200 fs/dcache.c:879
 dput+0x52/0x60 fs/dcache.c:928
 end_renaming fs/namei.c:4096 [inline]
 filename_renameat2+0x493/0x6e0 fs/namei.c:6146
 __do_sys_rename fs/namei.c:6188 [inline]
 __se_sys_rename+0x4a/0x1c0 fs/namei.c:6184
 __x64_sys_rename+0x31/0x40 fs/namei.c:6184
 x64_sys_call+0x2b3/0x3020 arch/x86/include/generated/asm/syscalls_64.h:83
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x12c/0x370 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x08200080 -> 0x00200180

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 3718 Comm: udevd Tainted: G        W           syzkaller #0 PREEMPT(full) 
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026
==================================================================

Crashes (17):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/02/28 04:16 upstream 4d349ee5c778 43249bac .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in __dentry_kill / d_make_discardable
2026/02/23 22:15 upstream 7dff99b35460 41d2fa6a .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in __dentry_kill / d_make_discardable
2026/02/23 10:20 upstream 6de23f81a5e0 6beca497 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in __dentry_kill / d_make_discardable
2026/02/20 07:15 upstream 8bf22c33e7a1 17d780d6 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in __dentry_kill / d_make_discardable
2026/02/18 15:34 upstream 2961f841b025 77d4d919 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in __dentry_kill / d_make_discardable
2026/02/06 11:13 upstream b7ff7151e653 f03c4191 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in __dentry_kill / d_make_discardable
2026/02/05 21:44 upstream 8fdb05de0e2d f03c4191 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in __dentry_kill / d_make_discardable
2026/02/03 22:28 upstream de0674d9bc69 42b01fab .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in __dentry_kill / d_make_discardable
2026/02/02 22:26 upstream dee65f79364c d78927dd .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in __dentry_kill / d_make_discardable
2026/01/29 11:01 upstream 8dfce8991b95 aeb6fdd5 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in __dentry_kill / d_make_discardable
2026/01/26 23:33 upstream fcb70a56f4d8 efb3e894 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in __dentry_kill / d_make_discardable
2026/01/26 11:47 upstream 63804fed149a a4c52dd6 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in __dentry_kill / d_make_discardable
2026/01/25 13:49 upstream d91a46d6805a 40acda8a .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in __dentry_kill / d_make_discardable
2026/01/23 23:12 upstream 5bde837031a3 4f25b9b4 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in __dentry_kill / d_make_discardable
2026/01/23 04:26 upstream c072629f05d7 82c9c083 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in __dentry_kill / d_make_discardable
2026/01/13 18:57 upstream b54345928fa1 d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in __dentry_kill / d_make_discardable
2026/01/04 16:38 upstream 54e82e93ca93 d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in __dentry_kill / d_make_discardable
* Struck through repros no longer work on HEAD.