On 13/11/2024 01:40, Darrick J. Wong wrote: >> Hmm, I guess I might have made that possible, though I'm certainly not >> familiar enough with the internals of nfsd to be able to test if I've done >> so. > AFAIK check_export() in fs/nfsd/export.c spells this it out: > > /* There are two requirements on a filesystem to be exportable. > * 1: We must be able to identify the filesystem from a number. > * either a device number (so FS_REQUIRES_DEV needed) > * or an FSID number (so NFSEXP_FSID or ->uuid is needed). > * 2: We must be able to find an inode from a filehandle. > * This means that s_export_op must be set. > * 3: We must not currently be on an idmapped mount. > */ > > Granted I've been wrong on account of stale docs before. :$ > > Though it would be kinda funny if you *could* mess with another > machine's processes over NFS. > > --D To be clear I'm not familiar enough with the workings of nfsd to tell if pidfs fails those requirements and therefore wouldn't become exportable as a result of this patch, though I gather from you're message that we're in the clear? Regardless I think my question is: do we think either those requirements could change in the future, or the properties of pidfs could change in the future, in ways that could accidentally make the filesystem exportable? I guess though that the same concern would apply to cgroupfs and it hasn't posed an issue so far. - Erin
