[moderation] [kernel?] KCSAN: data-race in dequeue_signal / ptrace_check_attach (12)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: dd6c438c3e64 Merge tag 'vfs-7.1-rc1.fixes' of git://git.ke..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=133e7702580000
kernel config: https://syzkaller.appspot.com/x/.config?x=9bed1befe3a428bc
dashboard link: https://syzkaller.appspot.com/bug?extid=317772dacbc1ea722bd2
compiler: Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8
CC: [linux-...@vger.kernel.org lu...@kernel.org pet...@infradead.org tg...@kernel.org]

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/cd551d2b03e4/disk-dd6c438c.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/aaf0bde313fe/vmlinux-dd6c438c.xz
kernel image: https://storage.googleapis.com/syzbot-assets/45ce1d7bcda4/bzImage-dd6c438c.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+317772...@syzkaller.appspotmail.com

UDC core: USB Raw Gadget: couldn't find an available UDC or it's busy
misc raw-gadget: fail, usb_gadget_register_driver returned -16
==================================================================
BUG: KCSAN: data-race in dequeue_signal / ptrace_check_attach

read-write to 0xffff88815484eb98 of 8 bytes by task 30405 on cpu 0:
dequeue_signal+0x308/0x3a0 kernel/signal.c:656
get_signal+0x375/0xf20 kernel/signal.c:2917
arch_do_signal_or_restart+0x96/0x450 arch/x86/kernel/signal.c:337
__exit_to_user_mode_loop kernel/entry/common.c:64 [inline]
exit_to_user_mode_loop+0x6a/0x6f0 kernel/entry/common.c:98
__exit_to_user_mode_prepare include/linux/irq-entry-common.h:207 [inline]
syscall_exit_to_user_mode_prepare include/linux/irq-entry-common.h:238 [inline]
syscall_exit_to_user_mode include/linux/entry-common.h:318 [inline]
do_syscall_64+0x232/0x3b0 arch/x86/entry/syscall_64.c:100
entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff88815484eb98 of 8 bytes by task 30399 on cpu 1:
ptrace_freeze_traced kernel/ptrace.c:189 [inline]
ptrace_check_attach+0xa9/0x280 kernel/ptrace.c:256
__do_sys_ptrace kernel/ptrace.c:1410 [inline]
__se_sys_ptrace+0xd3/0x2c0 kernel/ptrace.c:1388
__x64_sys_ptrace+0x55/0x70 kernel/ptrace.c:1388
x64_sys_call+0x287b/0x3020 arch/x86/include/generated/asm/syscalls_64.h:102
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0x12c/0x3b0 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x0000000000000000 -> 0x0000000008010000

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 30399 Comm: syz.5.8267 Tainted: G W syzkaller #0 PREEMPT(full)
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/18/2026
==================================================================


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