netbsd boot error: panic: UBSan: Undefined Behavior in /syzkaller/managers/netbsd-kubsan/kernel/sys/kern/vfs_mount.c:LINE, member access wi

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit: 101443cf No need to do the poll-during-autoconfiguration d..
git tree: netbsd
console output: https://syzkaller.appspot.com/x/log.txt?x=11a0fac1e00000
kernel config: https://syzkaller.appspot.com/x/.config?x=824b23e1f4b6c76b
dashboard link: https://syzkaller.appspot.com/bug?extid=c024c50570cccac51532
compiler: g++ (Ubuntu 5.4.0-6ubuntu1~16.04.12) 5.4.0 20160609

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+c024c5...@syzkaller.appspotmail.com

[ 1.0000000] panic: UBSan: Undefined Behavior in
/syzkaller/managers/netbsd-kubsan/kernel/sys/kern/vfs_mount.c:152:13,
member access within misaligned address 0xffff82f77fcc3008 for type 'struct
mount' which requires 64 byte alignment

[ 1.0000000] cpu0: Begin traceback...
[ 1.0000000] vpanic() at netbsd:vpanic+0x2aa sys/kern/subr_prf.c:336
[ 1.0000000] isAlreadyReported() at netbsd:isAlreadyReported
[ 1.0000000] HandleTypeMismatch.part.1() at
netbsd:HandleTypeMismatch.part.1+0xcc
[ 1.0000000] HandleTypeMismatch() at netbsd:HandleTypeMismatch+0x7b
sys/../common/lib/libc/misc/ubsan.c:408
[ 1.0000000] vfs_mountalloc() at netbsd:vfs_mountalloc+0x320
sys/kern/vfs_mount.c:152
[ 1.0000000] vfs_vnode_sysinit() at netbsd:vfs_vnode_sysinit+0x1e
sys/kern/vfs_vnode.c:379
[ 1.0000000] vntblinit() at netbsd:vntblinit+0x343 sys/kern/vfs_subr.c:141
[ 1.0000000] vfsinit() at netbsd:vfsinit+0x1c3 sys/kern/vfs_init.c:418
[ 1.0000000] main() at netbsd:main+0x2ea sys/kern/init_main.c:482
[ 1.0000000] cpu0: End traceback...
[ 1.0000000] fatal breakpoint trap in supervisor mode
[ 1.0000000] trap type 1 code 0 rip 0xffffffff8021e7cd cs 0x8 rflags
0x202 cr2 0 ilevel 0x8 rsp 0xffffffff8625d6f0
[ 1.0000000] curlwp 0xffffffff85344da0 pid 0.1 lowest kstack
0xffffffff862592c0
Stopped in pid 0.1 (system) at netbsd:breakpoint+0x5: leave
db{0}>


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