KCSAN: data-race in __ptrace_unlink / ptrace_stop (2)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 9c87c9f4 Merge tag 'arm-soc-fixes-v5.10-2' of git://git.ke..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=14d682f2500000
kernel config: https://syzkaller.appspot.com/x/.config?x=e0bbcd06922dbd46
dashboard link: https://syzkaller.appspot.com/bug?extid=4a13fc71ee115c447358
compiler: clang version 12.0.0 (https://github.com/llvm/llvm-project.git 913f6005669cfb590c99865a90bc51ed0983d09d)
CC: [ax...@kernel.dk chri...@brauner.io ebie...@xmission.com linux-...@vger.kernel.org liuzhi...@huawei.com 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+4a13fc...@syzkaller.appspotmail.com

==================================================================
BUG: KCSAN: data-race in __ptrace_unlink / ptrace_stop

read-write to 0xffff88810e06f064 of 4 bytes by task 23499 on cpu 1:
freezer_count include/linux/freezer.h:121 [inline]
freezable_schedule include/linux/freezer.h:173 [inline]
ptrace_stop+0x36e/0x620 kernel/signal.c:2216
ptrace_signal kernel/signal.c:2491 [inline]
get_signal+0xbed/0x1510 kernel/signal.c:2654
arch_do_signal+0x25/0x260 arch/x86/kernel/signal.c:811
exit_to_user_mode_loop kernel/entry/common.c:161 [inline]
exit_to_user_mode_prepare+0xde/0x170 kernel/entry/common.c:191
syscall_exit_to_user_mode+0x16/0x30 kernel/entry/common.c:266
do_syscall_64+0x45/0x80 arch/x86/entry/common.c:56
entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff88810e06f064 of 4 bytes by task 23500 on cpu 0:
__ptrace_unlink+0x185/0x2f0 kernel/ptrace.c:144
__ptrace_detach+0x1b/0x1a0 kernel/ptrace.c:528
exit_ptrace+0x93/0x160 kernel/ptrace.c:588
forget_original_parent kernel/exit.c:613 [inline]
exit_notify kernel/exit.c:653 [inline]
do_exit+0x11b3/0x15a0 kernel/exit.c:829
do_group_exit+0xc8/0x170 kernel/exit.c:906
get_signal+0xf9b/0x1510 kernel/signal.c:2758
arch_do_signal+0x25/0x260 arch/x86/kernel/signal.c:811
exit_to_user_mode_loop kernel/entry/common.c:161 [inline]
exit_to_user_mode_prepare+0xde/0x170 kernel/entry/common.c:191
syscall_exit_to_user_mode+0x16/0x30 kernel/entry/common.c:266
do_syscall_64+0x45/0x80 arch/x86/entry/common.c:56
entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 23500 Comm: syz-executor.5 Not tainted 5.10.0-rc4-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.