[moderation] [kernel?] KCSAN: data-race in prepare_signal / ptrace_attach (12)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 4bbf9020becb Linux 6.13-rc4
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1686d8c4580000
kernel config: https://syzkaller.appspot.com/x/.config?x=87d3cfca6847d1fa
dashboard link: https://syzkaller.appspot.com/bug?extid=ed249812ebd8b2fe23a4
compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
CC: [linux-...@vger.kernel.org ol...@redhat.com]

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/8e1301e51dba/disk-4bbf9020.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/0f070c40e189/vmlinux-4bbf9020.xz
kernel image: https://storage.googleapis.com/syzbot-assets/71e2a6659de1/bzImage-4bbf9020.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+ed2498...@syzkaller.appspotmail.com

==================================================================
BUG: KCSAN: data-race in prepare_signal / ptrace_attach

write to 0xffff88811776e330 of 4 bytes by task 10179 on cpu 0:
ptrace_attach+0x258/0x520 kernel/ptrace.c:462
__do_sys_ptrace kernel/ptrace.c:1276 [inline]
__se_sys_ptrace+0x149/0x2b0 kernel/ptrace.c:1258
__x64_sys_ptrace+0x55/0x70 kernel/ptrace.c:1258
x64_sys_call+0x2225/0x2dc0 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

read to 0xffff88811776e330 of 4 bytes by task 10180 on cpu 1:
prepare_signal+0x263/0x670 kernel/signal.c:901
__send_signal_locked+0x2f/0x780 kernel/signal.c:1052
send_signal_locked+0x28f/0x3a0 kernel/signal.c:1215
do_send_sig_info+0x9f/0xf0 kernel/signal.c:1268
do_send_specific kernel/signal.c:4091 [inline]
do_tkill kernel/signal.c:4112 [inline]
__do_sys_tkill kernel/signal.c:4147 [inline]
__se_sys_tkill+0x135/0x190 kernel/signal.c:4141
__x64_sys_tkill+0x31/0x40 kernel/signal.c:4141
x64_sys_call+0x281a/0x2dc0 arch/x86/include/generated/asm/syscalls_64.h:201
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: 0x00000000 -> 0x00010001

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 10180 Comm: syz.1.2207 Not tainted 6.13.0-rc4-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/13/2024
==================================================================


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[syzbot]

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