[syzbot] KASAN: out-of-bounds Read in do_exit

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit:    9ed13a17 Merge tag 'net-5.13-rc7' of git://git.kernel.org/..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=116c517bd00000
kernel config:  https://syzkaller.appspot.com/x/.config?x=bf635d6d1c7ebabc
dashboard link: https://syzkaller.appspot.com/bug?extid=b80bbdcca4c4dfaa189e
compiler:       Debian clang version 11.0.1-2

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+b80bbdcca4c4dfaa189e@xxxxxxxxxxxxxxxxxxxxxxxxx

==================================================================
BUG: KASAN: out-of-bounds in stack_not_used include/linux/sched/task_stack.h:101 [inline]
BUG: KASAN: out-of-bounds in check_stack_usage kernel/exit.c:711 [inline]
BUG: KASAN: out-of-bounds in do_exit+0x1c6b/0x23d0 kernel/exit.c:869
Read of size 8 at addr ffffc90017d60400 by task loop0/31717

CPU: 0 PID: 31717 Comm: loop0 Not tainted 5.13.0-rc6-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:79 [inline]
 dump_stack+0x202/0x31e lib/dump_stack.c:120
 print_address_description+0x5f/0x3b0 mm/kasan/report.c:233
 __kasan_report mm/kasan/report.c:419 [inline]
 kasan_report+0x15c/0x200 mm/kasan/report.c:436
 stack_not_used include/linux/sched/task_stack.h:101 [inline]
 check_stack_usage kernel/exit.c:711 [inline]
 do_exit+0x1c6b/0x23d0 kernel/exit.c:869
 kthread+0x3b8/0x3c0 kernel/kthread.c:315
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:294


Memory state around the buggy address:
 ffffc90017d60300: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffffc90017d60380: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>ffffc90017d60400: 07 07 07 07 07 07 07 07 00 00 00 00 00 00 00 00
                   ^
 ffffc90017d60480: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffffc90017d60500: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
==================================================================


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