assert "dupe == NULL" failed in uvm_page.c (5)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: f09b465a1938 remove unused variables
git tree: openbsd
console output: https://syzkaller.appspot.com/x/log.txt?x=16e4bbcd980000
kernel config: https://syzkaller.appspot.com/x/.config?x=7058272de1526588
dashboard link: https://syzkaller.appspot.com/bug?extid=cb2555c3bd673da0f6f4

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/229d1e7c6f02/disk-f09b465a.raw.xz
bsd.gdb: https://storage.googleapis.com/syzbot-assets/07ac92919791/bsd-f09b465a.gdb.xz
kernel image: https://storage.googleapis.com/syzbot-assets/f6c0013cd315/kernel-f09b465a.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+cb2555...@syzkaller.appspotmail.com

panic: kernel diagnostic assertion "dupe == NULL" failed: file "/syzkaller/managers/multicore/kernel/sys/uvm/uvm_page.c", line 144
Starting stack trace...
panic(ffffffff8339aa61) at panic+0x1d0 sys/kern/subr_prf.c:229
__assert(ffffffff833d5cfa,ffffffff833c6bb7,90,ffffffff8336d9a2) at __assert+0x29 sys/kern/subr_prf.c:-1
uvm_pagealloc_pg(fffffd8009043d40,fffffd800b026238,4ac9ea000,0) at uvm_pagealloc_pg+0x54b sys/uvm/uvm_page.c:707
uvm_pagealloc(fffffd800b026238,4ac9ea000,0,3) at uvm_pagealloc+0x252 sys/uvm/uvm_page.c:913
pmap_get_ptp(fffffd800b026200,9593d451000) at pmap_get_ptp+0x1d0 sys/arch/amd64/amd64/pmap.c:-1
pmap_enter(fffffd800b026200,9593d451000,6c3ca000,4,20) at pmap_enter+0x386 sys/arch/amd64/amd64/pmap.c:-1
uvm_fault_lower_lookup(ffff80002a370ad0,ffff80002a370b08,ffff80002a370a50) at uvm_fault_lower_lookup+0x3d6 sys/uvm/uvm_fault.c:-1
uvm_fault_lower(ffff80002a370ad0,ffff80002a370b08,ffff80002a370a50) at uvm_fault_lower+0x89 sys/uvm/uvm_fault.c:1348
uvm_fault(fffffd806bcc0d78,9593d452000,0,4) at uvm_fault+0x274 sys/uvm/uvm_fault.c:-1
upageflttrap(ffff80002a370c70,9593d4522cb) at upageflttrap+0xa9 sys/arch/amd64/amd64/trap.c:192
usertrap(ffff80002a370c70) at usertrap+0x42f sys/arch/amd64/amd64/trap.c:622
recall_trap() at recall_trap+0x8
end of kernel
end trace frame: 0x79400ebb0ce0, count: 245
End of stack trace.


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