[moderation] [kernel?] KCSAN: data-race in dequeue_signal / ptrace_check_attach (9)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: de9c2c66ad8e Linux 6.11-rc2
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=138958d9980000
kernel config: https://syzkaller.appspot.com/x/.config?x=cb57e6ebf675f9d2
dashboard link: https://syzkaller.appspot.com/bug?extid=1d7d8cd8a77d22fc2aec
compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
CC: [linux-...@vger.kernel.org lu...@kernel.org pet...@infradead.org tg...@linutronix.de]

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/8b200dded886/disk-de9c2c66.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/c2d5bc7a48ee/vmlinux-de9c2c66.xz
kernel image: https://storage.googleapis.com/syzbot-assets/8d87cc5249ae/bzImage-de9c2c66.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+1d7d8c...@syzkaller.appspotmail.com

==================================================================
BUG: KCSAN: data-race in dequeue_signal / ptrace_check_attach

read-write to 0xffff888107afb6a8 of 8 bytes by task 10055 on cpu 0:
dequeue_signal+0x3de/0x430 kernel/signal.c:685
get_signal+0x37d/0x1080 kernel/signal.c:2796
arch_do_signal_or_restart+0x95/0x4b0 arch/x86/kernel/signal.c:310
exit_to_user_mode_loop kernel/entry/common.c:111 [inline]
exit_to_user_mode_prepare include/linux/entry-common.h:328 [inline]
__syscall_exit_to_user_mode_work kernel/entry/common.c:207 [inline]
syscall_exit_to_user_mode+0x59/0x130 kernel/entry/common.c:218
do_syscall_64+0xd6/0x1c0 arch/x86/entry/common.c:89
entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff888107afb6a8 of 8 bytes by task 10051 on cpu 1:
ptrace_freeze_traced kernel/ptrace.c:189 [inline]
ptrace_check_attach+0x7f/0x290 kernel/ptrace.c:256
__do_sys_ptrace kernel/ptrace.c:1280 [inline]
__se_sys_ptrace+0xd4/0x2b0 kernel/ptrace.c:1258
__x64_sys_ptrace+0x55/0x70 kernel/ptrace.c:1258
x64_sys_call+0x2913/0x2d60 arch/x86/include/generated/asm/syscalls_64.h:102
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0xc9/0x1c0 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x0000000000000000 -> 0x0000000008010000

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 10051 Comm: syz.1.2328 Not tainted 6.11.0-rc2-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 06/27/2024
==================================================================


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[syzbot]

Auto-closing this bug as obsolete.
Crashes did not happen for a while, no reproducer and no activity.