syzbot


KCSAN: data-race in anon_pipe_write / opipe_prep

Status: moderation: reported on 2025/12/18 19:46
Subsystems: fs
[Documentation on labels]
Reported-by: syzbot+fdd7d4c7849e37294bdf@syzkaller.appspotmail.com
First crash: 1d18h, last: 1d18h

Sample crash report:
==================================================================
BUG: KCSAN: data-race in anon_pipe_write / opipe_prep

write to 0xffff8881284244d0 of 4 bytes by task 13043 on cpu 0:
 anon_pipe_write+0x59a/0xb30 fs/pipe.c:530
 new_sync_write fs/read_write.c:593 [inline]
 vfs_write+0x52a/0x960 fs/read_write.c:686
 ksys_write+0xda/0x1a0 fs/read_write.c:738
 __do_sys_write fs/read_write.c:749 [inline]
 __se_sys_write fs/read_write.c:746 [inline]
 __x64_sys_write+0x40/0x50 fs/read_write.c:746
 x64_sys_call+0x2847/0x3000 arch/x86/include/generated/asm/syscalls_64.h:2
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xd8/0x2c0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff8881284244d0 of 4 bytes by task 13041 on cpu 1:
 pipe_is_full include/linux/pipe_fs_i.h:208 [inline]
 opipe_prep+0x26/0x1e0 fs/splice.c:1688
 do_tee+0x296/0x910 fs/splice.c:1965
 __do_sys_tee fs/splice.c:1995 [inline]
 __se_sys_tee+0x93/0x130 fs/splice.c:1979
 __x64_sys_tee+0x55/0x70 fs/splice.c:1979
 x64_sys_call+0xeb4/0x3000 arch/x86/include/generated/asm/syscalls_64.h:277
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xd8/0x2c0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x00000000 -> 0x00000001

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 13041 Comm: syz.2.2374 Tainted: G        W           syzkaller #0 PREEMPT(voluntary) 
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
==================================================================

Crashes (1):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2025/12/18 19:45 upstream ea1013c15392 d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in anon_pipe_write / opipe_prep
* Struck through repros no longer work on HEAD.