Error trying to use ISO on SMB share: "Failed to get "consistent read" lock: Input/output error"

If I try to create a VM using an ISO on an SMB share (mounted at /mnt/data), it fails:
```
libvirt.libvirtError: internal error: QEMU unexpectedly closed the monitor (vm='bios1'): 2025-01-23T22:54:02.230636Z qemu-system-x86_64: -device {"driver":"ide-cd","bus":"ide.0","drive":"libvirt-1-storage","id":"sata0-0-0","bootindex":1}: Failed to get "consistent read" lock: Input/output error
Is another process using the image [/run/user/1000/doc/98240bae/Fedora-KDE-Desktop-Live-Rawhide-20250123.n.0.x86_64.iso]?
```
If I copy the ISO to my Downloads directory and use that, it works fine. I tried giving virt-manager read-only access to /mnt/data via flatseal, but it didn't help.

This works OK with the flathub Boxes flatpak, so it must be possible...