[Virtio-fs] [virtiofsd] Issue opened: Fix listxattr() response when name list is empty

[virtiofs-bot at sinrega.org]

FUSE_LISTXATTR returns a xattr name list. It is possible that all xattrs have been filtered out by server and resulting name list is empty. As of now rust version of code writes a null byte to client supplied buffer. This fails the kernel fuse code verification and return -EIO to user space.

Fix this by not writing a single null byte. Simply send a response back with error code 0 and virtiofs kernel code should be able to handle it and update variable argument size to 0.
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https://gitlab.com/virtio-fs/virtiofsd/-/issues/55