KCSAN: data-race in __se_sys_inotify_add_watch / fsnotify_handle_inode_event

Status: upstream: reported C repro on 2026/09/25 14:42
Labels: prio:low race:harmful
[Documentation on labels]
Reported-by: syzbot+181b8b439f5207144b16@syzkaller.appspotmail.com
First crash: 4h44m, last: 4h44m
▶ ▼ ✨ AI Jobs (2)
ID Workflow Result Correct Bug Created Started Finished Revision
c6311923 assessment-security DenialOfService: ❌ Exploitable: ❌ FilesystemTrigger: ❌ NetworkTrigger: ❌ PeripheralTrigger: ❌ RemoteTrigger: ❌ Unprivileged: ✅ UserNamespace: ✅ VMGuestTrigger: ❌ VMHostTrigger: ❌ ❓ KCSAN: data-race in __se_sys_inotify_add_watch / fsnotify_handle_inode_event 2026/09/25 14:30 2026/09/25 14:30 2026/09/25 14:32 f281d9d2
22dd8903 assessment-kcsan Benign: ❌ ❓ KCSAN: data-race in __se_sys_inotify_add_watch / fsnotify_handle_inode_event 2026/09/25 14:06 2026/09/25 14:06 2026/09/25 14:42 f281d9d2
▶ ▼ Discussions (1)
Title Replies (including bot) Last reply
[syzbot] KCSAN: data-race in __se_sys_inotify_add_watch / fsnotify_handle_inode_event 0 (1) 2026/09/25 14:42

Sample crash report:
==================================================================
BUG: KCSAN: data-race in __se_sys_inotify_add_watch / fsnotify_handle_inode_event

write to 0xffff88811afe9be0 of 4 bytes by task 3651 on cpu 0:
 inotify_update_existing_watch fs/notify/inotify/inotify_user.c:558 [inline]
 inotify_update_watch fs/notify/inotify/inotify_user.c:632 [inline]
 __do_sys_inotify_add_watch fs/notify/inotify/inotify_user.c:769 [inline]
 __se_sys_inotify_add_watch+0x2ea/0x720 fs/notify/inotify/inotify_user.c:717
 __x64_sys_inotify_add_watch+0x43/0x50 fs/notify/inotify/inotify_user.c:717
 x64_sys_call+0xa19/0x2550 arch/x86/include/generated/asm/syscalls_64.h:255
 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
 do_syscall_64+0x112/0x360 arch/x86/entry/syscall_64.c:84
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff88811afe9be0 of 4 bytes by task 3653 on cpu 1:
 fsnotify_handle_inode_event+0x18a/0x230 fs/notify/fsnotify.c:272
 fsnotify_handle_event fs/notify/fsnotify.c:330 [inline]
 send_to_group fs/notify/fsnotify.c:378 [inline]
 fsnotify+0x16ae/0x1860 fs/notify/fsnotify.c:597
 __fsnotify_parent+0x2f8/0x3a0 fs/notify/fsnotify.c:241
 fsnotify_parent include/linux/fsnotify.h:96 [inline]
 fsnotify_path include/linux/fsnotify.h:113 [inline]
 fsnotify_file include/linux/fsnotify.h:127 [inline]
 fsnotify_close include/linux/fsnotify.h:461 [inline]
 __fput+0x1e2/0x630 fs/file_table.c:498
 fput_close_sync+0xad/0x190 fs/file_table.c:617
 __do_sys_close fs/open.c:1560 [inline]
 __se_sys_close fs/open.c:1545 [inline]
 __x64_sys_close+0x55/0xf0 fs/open.c:1545
 x64_sys_call+0x812/0x2550 arch/x86/include/generated/asm/syscalls_64.h:4
 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
 do_syscall_64+0x112/0x360 arch/x86/entry/syscall_64.c:84
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x00002018 -> 0x00000000

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 3653 Comm: syz-executor126 Not tainted syzkaller #0 PREEMPT(lazy) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
==================================================================

Crashes (1):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/09/25 14:06 git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git f49a343b305c 0281b448 .config console log report C ci2-upstream-kcsan-gce KCSAN: data-race in __se_sys_inotify_add_watch / fsnotify_handle_inode_event
* Struck through repros no longer work on HEAD.