Crash when using kqueue (via epoll-shim) on DMABUF handle

[jbeich]

Describe the bug
After gamescope started using epoll FreeBSD kernel crashes.

FreeBSD version

$ uname -aKU
FreeBSD example.tld 15.0-CURRENT #0 main-n266825-59cf3436dce3: Wed Dec  6 07:38:33 UTC 2023 [email protected]:/usr/obj/usr/src/amd64.amd64/sys/MYKERNEL amd64 1500005 1500005

PCI Info

pciconf -lv

$ pciconf -lv | fgrep -A4 vga
vgapci1@pci0:0:2:0:     class=0x030000 rev=0x06 hdr=0x00 vendor=0x8086 device=0x1912 subvendor=0x1462 subdevice=0x7968
    vendor     = 'Intel Corporation'
    device     = 'HD Graphics 530'
    class      = display
    subclass   = VGA

DRM KMOD version

$ pkg query -x '%n %v' 'drm.*kmod'
drm-515-kmod-5.15.118_2

To Reproduce

1. Ensure GPU supports Vulkan (required by gamescope)
2. Apply pending gamescope 3.13.17 update
3. Install gamescope and vulkan-tools
4. Run env INTEL_DEBUG=norbc gamescope -- vkcube-xcb
5. Kernel panic

Screenshots
I can't provide a backtrace as DDB fails to save and reboot for some reason