syzbot


KCSAN: data-race in memcpy_and_pad / zap_other_threads

Status: moderation: reported on 2025/08/28 14:58
Subsystems: kernel
[Documentation on labels]
Reported-by: syzbot+09ff6ebfc22191ecf441@syzkaller.appspotmail.com
First crash: 7h49m, last: 7h49m

Sample crash report:
==================================================================
BUG: KCSAN: data-race in memcpy_and_pad / zap_other_threads

read-write to 0xffff888104b40538 of 8 bytes by task 26415 on cpu 1:
 task_clear_jobctl_pending kernel/signal.c:339 [inline]
 zap_other_threads+0x114/0x290 kernel/signal.c:1345
 do_group_exit+0xe4/0x140 kernel/exit.c:1097
 __do_sys_exit_group kernel/exit.c:1113 [inline]
 __se_sys_exit_group kernel/exit.c:1111 [inline]
 __x64_sys_exit_group+0x1f/0x20 kernel/exit.c:1111
 x64_sys_call+0x2fe2/0x2ff0 arch/x86/include/generated/asm/syscalls_64.h:232
 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 0xffff888104b40000 of 3264 bytes by task 26416 on cpu 0:
 memcpy_and_pad+0x48/0x80 lib/string_helpers.c:1007
 arch_dup_task_struct+0x2c/0x40 arch/x86/kernel/process.c:98
 dup_task_struct+0x83/0x6a0 kernel/fork.c:878
 copy_process+0x399/0x2000 kernel/fork.c:2004
 create_io_thread+0x93/0xc0 kernel/fork.c:2553
 io_sq_offload_create+0x652/0x850 io_uring/sqpoll.c:491
 io_uring_create+0x42e/0x610 io_uring/io_uring.c:3808
 io_uring_setup io_uring/io_uring.c:3891 [inline]
 __do_sys_io_uring_setup io_uring/io_uring.c:3925 [inline]
 __se_sys_io_uring_setup+0x1f7/0x210 io_uring/io_uring.c:3916
 __x64_sys_io_uring_setup+0x31/0x40 io_uring/io_uring.c:3916
 x64_sys_call+0x2b21/0x2ff0 arch/x86/include/generated/asm/syscalls_64.h:426
 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

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 26416 Comm: syz.0.7528 Not tainted syzkaller #0 PREEMPT(voluntary) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2025
==================================================================

Crashes (1):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2025/08/28 14:58 upstream 07d9df80082b e12e5ba4 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in memcpy_and_pad / zap_other_threads
* Struck through repros no longer work on HEAD.