kernel panic: mntchk 3: can't happen

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit: f89b6d306593 alarm: Do not allow callbacks to block
git tree: https://github.com/akaros/akaros.git master
console output: https://syzkaller.appspot.com/x/log.txt?x=15f974f5400000
kernel config: https://syzkaller.appspot.com/x/.config?x=bc709c3b83482973
dashboard link: https://syzkaller.appspot.com/bug?extid=71b4d03a666c50b6e2e8
compiler:

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+71b4d0...@syzkaller.appspotmail.com

kernel panic at kern/drivers/dev/mnt.c:1201, from core 0: mntchk 3: can't
happen
Stack Backtrace on Core 0:
#01 [<0xffffffffc200a33c>] in backtrace at src/kdebug.c:229
#02 [<0xffffffffc2009acd>] in _panic at src/init.c:267
#03 [<0xffffffffc207f921>] in mntchk at drivers/dev/mnt.c:1201
#04 [<0xffffffffc207fb8b>] in mntopencreate at drivers/dev/mnt.c:546
#05 [<0xffffffffc207fd88>] in mntopen at drivers/dev/mnt.c:580
#06 [<0xffffffffc2033960>] in __namec_from at src/ns/chan.c:1233
#07 [<0xffffffffc203413f>] in namec at src/ns/chan.c:1517
#08 [<0xffffffffc20414b6>] in sysopenat at src/ns/sysfile.c:592
#09 [<0xffffffffc205934f>] in sys_openat at src/syscall.c:1724
#10 [<0xffffffffc2059f09>] in syscall at src/syscall.c:2465
#11 [<0xffffffffc205a0d4>] in run_local_syscall at src/syscall.c:2500
#12 [<0xffffffffc205a609>] in prep_syscalls at src/syscall.c:2520
#13 [<0xffffffffc20abc0a>] in sysenter_callwrapper at arch/x86/trap.c:854


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[syzbot]

Auto-closing this bug as obsolete.
Crashes did not happen for a while, no reproducer and no activity.