uvm_fault: proc_trampoline

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 85fbf21ae5ae IP multicast sysctl mrtmfc must not write out..
git tree: openbsd
console output: https://syzkaller.appspot.com/x/log.txt?x=10ca81d3180000
kernel config: https://syzkaller.appspot.com/x/.config?x=7058272de1526588
dashboard link: https://syzkaller.appspot.com/bug?extid=f5d26bc5df263ec47ec3

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/7385c31bb738/disk-85fbf21a.raw.xz
bsd.gdb: https://storage.googleapis.com/syzbot-assets/4559a9e48be8/bsd-85fbf21a.gdb.xz
kernel image: https://storage.googleapis.com/syzbot-assets/167034b9f857/kernel-85fbf21a.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+f5d26b...@syzkaller.appspotmail.com

uvm_fault(fffffd806890b378,b94f063000,0,4) at uvm_fault+0x255 sys/uvm/uvm_fault.c:637
upageflttrap(ffff800033f40640,b94f063d6b) at upageflttrap+0x8b sys/arch/amd64/amd64/trap.c:188
usertrap(ffff800033f40640) at usertrap+0x227 sys/arch/amd64/amd64/trap.c:436
recall_trap() at recall_trap+0x8
end of kernel
end trace frame: 0x7275595db810, count: -21
ddb{0}> machine ddbcpu 1
Stopped at proc_trampoline+0xc7: movl $0,%gs:0x660
proc_trampoline() at proc_trampoline+0xc7
end of kernel
end trace frame: 0x7275595db600, count: 14
ddb{1}> trace
proc_trampoline() at proc_trampoline+0xc7
end of kernel
end trace frame: 0x7275595db600, count: -1


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