KCSAN: data-race in complete_signal / ptrace_attach (2)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 0062442e Merge tag 'for-linus' of git://git.kernel.org/pub..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=12ecc6a1500000
kernel config: https://syzkaller.appspot.com/x/.config?x=671e27f23e60a67b
dashboard link: https://syzkaller.appspot.com/bug?extid=d33cd1e392a2a2a90c70
compiler: clang version 12.0.0 (https://github.com/llvm/llvm-project.git 913f6005669cfb590c99865a90bc51ed0983d09d)
CC: [linux-...@vger.kernel.org ol...@redhat.com]

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

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+d33cd1...@syzkaller.appspotmail.com

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

write to 0xffff888137010068 of 4 bytes by task 18535 on cpu 1:
ptrace_attach+0x217/0x4b0 kernel/ptrace.c:413
__do_sys_ptrace kernel/ptrace.c:1262 [inline]
__se_sys_ptrace+0xc1/0x2e0 kernel/ptrace.c:1242
__x64_sys_ptrace+0x51/0x60 kernel/ptrace.c:1242
do_syscall_64+0x39/0x80 arch/x86/entry/common.c:46
entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff888137010068 of 4 bytes by task 18538 on cpu 0:
complete_signal+0x455/0x5f0 kernel/signal.c:1034
__send_signal+0x666/0x780 kernel/signal.c:1181
send_signal+0x39f/0x3d0 kernel/signal.c:1242
do_send_sig_info+0x9b/0xe0 kernel/signal.c:1291
do_send_specific kernel/signal.c:3799 [inline]
do_tkill kernel/signal.c:3825 [inline]
__do_sys_tkill kernel/signal.c:3860 [inline]
__se_sys_tkill+0x12b/0x180 kernel/signal.c:3854
__x64_sys_tkill+0x2d/0x40 kernel/signal.c:3854
do_syscall_64+0x39/0x80 arch/x86/entry/common.c:46
entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 18538 Comm: syz-executor.3 Not tainted 5.10.0-rc3-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
==================================================================


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[syzbot]

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