KCSAN: data-race in futex_wait_queue_me / prepare_signal (2)

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit: 672f9255 Merge tag 'ceph-for-5.8-rc2' of git://github.com/..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=164568b5100000
kernel config: https://syzkaller.appspot.com/x/.config?x=8d84808839c665b5
dashboard link: https://syzkaller.appspot.com/bug?extid=730a2bbd66878efe4a5a
compiler: clang version 11.0.0 (https://github.com/llvm/llvm-project.git ca2dcbd030eadbf0aa9b660efe864ff08af6e18b)
CC: [dvh...@infradead.org linux-...@vger.kernel.org mi...@redhat.com pet...@infradead.org tg...@linutronix.de]

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

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+730a2b...@syzkaller.appspotmail.com

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

write to 0xffff888126bf0064 of 4 bytes by task 8629 on cpu 1:
freezer_do_not_count include/linux/freezer.h:109 [inline]
freezable_schedule include/linux/freezer.h:171 [inline]
futex_wait_queue_me+0x186/0x250 kernel/futex.c:2634
futex_wait+0x153/0x3a0 kernel/futex.c:2740
do_futex+0x144a/0x21b0 kernel/futex.c:3811
__do_sys_futex kernel/futex.c:3872 [inline]
__se_sys_futex+0x26d/0x330 kernel/futex.c:3840
__x64_sys_futex+0x74/0x80 kernel/futex.c:3840
do_syscall_64+0x71/0x120 arch/x86/entry/common.c:359
entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff888126bf0064 of 4 bytes by task 8627 on cpu 0:
sig_task_ignored kernel/signal.c:94 [inline]
sig_ignored kernel/signal.c:119 [inline]
prepare_signal+0x88d/0xdb0 kernel/signal.c:961
__send_signal+0x64/0x7d0 kernel/signal.c:1081
send_signal+0x398/0x3e0 kernel/signal.c:1241
do_send_sig_info+0x9b/0xe0 kernel/signal.c:1290
do_send_specific+0xc7/0x100 kernel/signal.c:3780
do_tkill kernel/signal.c:3806 [inline]
__do_sys_tgkill kernel/signal.c:3825 [inline]
__se_sys_tgkill kernel/signal.c:3819 [inline]
__x64_sys_tgkill+0x108/0x140 kernel/signal.c:3819
do_syscall_64+0x71/0x120 arch/x86/entry/common.c:359
entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 8627 Comm: syz-fuzzer Not tainted 5.8.0-rc1-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.