syzbot

ID	Workflow	Result	Correct	Bug	Created	Started	Finished	Revision	Error
dd0fa85b-0a8d-4e57-b593-4ea8b8abf367	assessment-kcsan		💥	KCSAN: data-race in vfs_fsync_range / writeback_single_inode (7)	2026/01/09 13:37	2026/01/09 13:37	2026/01/09 13:42	533546563b43424f499d2593e18f52d248283b42	failed to load compile commands: open /usr/local/google/home/dvyukov/syzkaller/agent/workdir/cache/build/b677fe55e64143439ed94d655a9cc051c7486eca/compile_commands.json: no such file or directory

==================================================================
BUG: KCSAN: data-race in vfs_fsync_range / writeback_single_inode

write to 0xffff888132403168 of 4 bytes by task 5120 on cpu 0:
 writeback_single_inode+0x150/0x3f0 fs/fs-writeback.c:1837
 sync_inode_metadata+0x5b/0x90 fs/fs-writeback.c:2923
 generic_buffers_fsync_noflush+0xd9/0x120 fs/buffer.c:619
 ext4_fsync_nojournal fs/ext4/fsync.c:88 [inline]
 ext4_sync_file+0x1ab/0x690 fs/ext4/fsync.c:147
 vfs_fsync_range+0x10d/0x130 fs/sync.c:187
 generic_write_sync include/linux/fs.h:3048 [inline]
 ext4_buffered_write_iter+0x34f/0x3c0 fs/ext4/file.c:305
 ext4_file_write_iter+0x387/0xf60 fs/ext4/file.c:-1
 iter_file_splice_write+0x666/0xa60 fs/splice.c:738
 do_splice_from fs/splice.c:938 [inline]
 direct_splice_actor+0x156/0x2a0 fs/splice.c:1161
 splice_direct_to_actor+0x312/0x680 fs/splice.c:1105
 do_splice_direct_actor fs/splice.c:1204 [inline]
 do_splice_direct+0xda/0x150 fs/splice.c:1230
 do_sendfile+0x380/0x650 fs/read_write.c:1370
 __do_sys_sendfile64 fs/read_write.c:1431 [inline]
 __se_sys_sendfile64 fs/read_write.c:1417 [inline]
 __x64_sys_sendfile64+0x105/0x150 fs/read_write.c:1417
 x64_sys_call+0x2bb4/0x3000 arch/x86/include/generated/asm/syscalls_64.h:41
 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 0xffff888132403168 of 4 bytes by task 5132 on cpu 1:
 vfs_fsync_range+0x9b/0x130 fs/sync.c:185
 generic_write_sync include/linux/fs.h:3048 [inline]
 ext4_buffered_write_iter+0x34f/0x3c0 fs/ext4/file.c:305
 ext4_file_write_iter+0x387/0xf60 fs/ext4/file.c:-1
 iter_file_splice_write+0x666/0xa60 fs/splice.c:738
 do_splice_from fs/splice.c:938 [inline]
 direct_splice_actor+0x156/0x2a0 fs/splice.c:1161
 splice_direct_to_actor+0x312/0x680 fs/splice.c:1105
 do_splice_direct_actor fs/splice.c:1204 [inline]
 do_splice_direct+0xda/0x150 fs/splice.c:1230
 do_sendfile+0x380/0x650 fs/read_write.c:1370
 __do_sys_sendfile64 fs/read_write.c:1431 [inline]
 __se_sys_sendfile64 fs/read_write.c:1417 [inline]
 __x64_sys_sendfile64+0x105/0x150 fs/read_write.c:1417
 x64_sys_call+0x2bb4/0x3000 arch/x86/include/generated/asm/syscalls_64.h:41
 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: 0x00000070 -> 0x00000002

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 5132 Comm: syz.5.342 Not tainted syzkaller #0 PREEMPT(voluntary) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/02/2025
==================================================================

Seq	Timestamp	Type	Name	Duration
0/0	2026/01/09 13:37	flow	assessment-kcsan	4m Model: unknown Error: failed to load compile commands: open /usr/local/google/home/dvyukov/syzkaller/agent/workdir/cache/build/b677fe55e64143439ed94d655a9cc051c7486eca/compile_commands.json: no such file or directory
1/1	2026/01/09 13:37	action	kernel-checkouter	0m Model: unknown Results: map[KernelSrc:/usr/local/google/home/dvyukov/syzkaller/agent/workdir/cache/src/0529266fcead13ab3e8024f282a466886e3a614d]
2/1	2026/01/09 13:38	action	kernel-builder	3m Model: unknown Results: map[KernelObj:/usr/local/google/home/dvyukov/syzkaller/agent/workdir/cache/build/b677fe55e64143439ed94d655a9cc051c7486eca]
3/1	2026/01/09 13:42	action	codesearch-prepare	0m Model: unknown Error: failed to load compile commands: open /usr/local/google/home/dvyukov/syzkaller/agent/workdir/cache/build/b677fe55e64143439ed94d655a9cc051c7486eca/compile_commands.json: no such file or directory Results: map[Index:codesearch-index]