syzbot

uvm_fault(fffffd806c62dd70,32cb9afa000,0,4) at uvm_fault+0x274 sys/uvm/uvm_fault.c:-1
upageflttrap(ffff800030fa75f0,32cb9afa960) at upageflttrap+0xa9 sys/arch/amd64/amd64/trap.c:192
usertrap(ffff800030fa75f0) at usertrap+0x430 sys/arch/amd64/amd64/trap.c:640
recall_trap() at recall_trap+0x8
end of kernel
end trace frame: 0x7087a1d095e0, count: -16
ddb{0}> machine ddbcpu 1
Stopped at      db_enter+0x25:  addq    $0x8,%rsp
ddb{1}> trace
db_enter() at db_enter+0x25 sys/arch/amd64/amd64/db_interface.c:438
witness_checkorder(fffffd806fb98e98,9,0) at witness_checkorder+0x10d1 sys/kern/subr_witness.c:-1
rw_do_enter_write(fffffd806fb98e80,1) at rw_do_enter_write+0xba sys/kern/kern_rwlock.c:234
rrw_enter(fffffd806fb98e80,1) at rrw_enter+0xc6 sys/kern/kern_rwlock.c:621
VOP_LOCK(fffffd806fca7010,2001) at VOP_LOCK+0xbd sys/kern/vfs_vops.c:527
vn_lock(fffffd806fca7010,2001) at vn_lock+0xa4 sys/kern/vfs_vnops.c:576
vn_closefile(fffffd806ad94d68,ffff80003c3e2fb8) at vn_closefile+0x111 vn_close sys/kern/vfs_vnops.c:298 [inline]
vn_closefile(fffffd806ad94d68,ffff80003c3e2fb8) at vn_closefile+0x111 sys/kern/vfs_vnops.c:621
fdrop(fffffd806ad94d68,ffff80003c3e2fb8) at fdrop+0x121 sys/kern/kern_descrip.c:1281
knote_remove(ffff80003c3e2fb8,fffffd8072020000,fffffd8072020090,4,0) at knote_remove+0x368 sys/kern/kern_event.c:2168
knote_fdclose(ffff80003c3e2fb8,4) at knote_fdclose+0xf9 sys/kern/kern_event.c:2203
fdrelease(ffff80003c3e2fb8,4) at fdrelease+0xf9 sys/kern/kern_descrip.c:761
syscall(ffff80003c3d5d50) at syscall+0xbd4 mi_syscall sys/sys/syscall_mi.h:176 [inline]
syscall(ffff80003c3d5d50) at syscall+0xbd4 sys/arch/amd64/amd64/trap.c:783
Xsyscall() at Xsyscall+0x128
end of kernel
end trace frame: 0x8535a86f1c0, count: -13