KCSAN: data-race in exit_signals / get_task_mm (3)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 3552c370 Merge tag 'nfsd-5.10-1' of git://linux-nfs.org/~b..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=11a32732500000
kernel config: https://syzkaller.appspot.com/x/.config?x=671e27f23e60a67b
dashboard link: https://syzkaller.appspot.com/bug?extid=aee3c7a94a40fb45af7c
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+aee3c7...@syzkaller.appspotmail.com

==================================================================
BUG: KCSAN: data-race in exit_signals / get_task_mm

read-write to 0xffff88800a875064 of 4 bytes by task 22460 on cpu 0:
exit_signals+0x108/0x530 kernel/signal.c:2846
do_exit+0x158/0x15a0 kernel/exit.c:762
do_group_exit+0xa0/0x170 kernel/exit.c:903
__do_sys_exit_group+0xb/0x10 kernel/exit.c:914
__se_sys_exit_group+0x5/0x10 kernel/exit.c:912
__x64_sys_exit_group+0x16/0x20 kernel/exit.c:912
do_syscall_64+0x39/0x80 arch/x86/entry/common.c:46
entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff88800a875064 of 4 bytes by task 4886 on cpu 1:
get_task_mm+0x3e/0x90 kernel/fork.c:1209
get_task_cmdline fs/proc/base.c:348 [inline]
proc_pid_cmdline_read+0x87/0x650 fs/proc/base.c:368
vfs_read+0x154/0x5c0 fs/read_write.c:494
ksys_read+0xce/0x180 fs/read_write.c:634
__do_sys_read fs/read_write.c:644 [inline]
__se_sys_read fs/read_write.c:642 [inline]
__x64_sys_read+0x3e/0x50 fs/read_write.c:642
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: 1 PID: 4886 Comm: systemd-journal 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.