KCSAN: data-race in do_signal_stop / ns_capable

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: aae5ab85 Merge tag 'riscv-for-linus-5.10-rc6' of git://git..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=12b3dcc9500000
kernel config: https://syzkaller.appspot.com/x/.config?x=9b9b19d1bde60f8d
dashboard link: https://syzkaller.appspot.com/bug?extid=a1efbd1f0915d739a8a4
compiler: clang version 12.0.0 (https://github.com/llvm/llvm-project.git 913f6005669cfb590c99865a90bc51ed0983d09d)
CC: [linux-...@vger.kernel.org linux-secu...@vger.kernel.org se...@hallyn.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+a1efbd...@syzkaller.appspotmail.com

==================================================================
BUG: KCSAN: data-race in do_signal_stop / ns_capable

read-write to 0xffff88801f4fb064 of 4 bytes by task 25816 on cpu 1:
ns_capable_common kernel/capability.c:377 [inline]
ns_capable+0x79/0xa0 kernel/capability.c:396
may_mount fs/namespace.c:1693 [inline]
can_umount fs/namespace.c:1715 [inline]
path_umount+0x90/0xa20 fs/namespace.c:1733
ksys_umount fs/namespace.c:1754 [inline]
__do_sys_umount fs/namespace.c:1759 [inline]
__se_sys_umount fs/namespace.c:1757 [inline]
__x64_sys_umount+0x8b/0xb0 fs/namespace.c:1757
do_syscall_64+0x39/0x80 arch/x86/entry/common.c:46
entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff88801f4fb064 of 4 bytes by task 25806 on cpu 0:
task_set_jobctl_pending kernel/signal.c:291 [inline]
do_signal_stop+0x32e/0x6b0 kernel/signal.c:2355
get_signal+0xa83/0x1510 kernel/signal.c:2718
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: 25806 Comm: syz-executor.3 Not tainted 5.10.0-rc5-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.