Vivek Goyal <vgoyal@xxxxxxxxxx> writes: > On Mon, Dec 07, 2020 at 10:22:35PM +0100, Dominick Grift wrote: >> Vivek Goyal <vgoyal@xxxxxxxxxx> writes: >> >> > On Mon, Dec 07, 2020 at 10:03:24AM -0500, Paul Moore wrote: >> >> On Mon, Dec 7, 2020 at 9:43 AM Ondrej Mosnacek <omosnace@xxxxxxxxxx> wrote: >> >> > >> >> > Hi everyone, >> >> > >> >> > In [1] we ran into a problem with the current handling of filesystem >> >> > labeling rules. Basically, it is only possible to specify either >> >> > genfscon or fs_use_xattr for a given filesystem, but in the case of >> >> > virtiofs, certain mounts may support security xattrs, while other ones >> >> > may not. >> >> >> > >> > [ cc virtio-fs list and miklos ] >> >> Quickly skimming the linked GH issue, it appears that the problem >> >> really lies in the fact that virtiofs allows one to enable/disable >> >> xattrs at mount time. What isn't clear to me is why one would need to >> >> disable xattrs, can you explain that use case? Why does enabling >> >> xattrs in virtiofs cause problems? >> > >> > Its not exactly a mount time option. Its a virtiofs file server option. >> > >> > xattr support by default is disabled because it has performance >> > penalty. Users can enable it if they want to. >> >> if SELinux is enabled then you should preferably just use fs_use xattr unconditionally >> >> > >> > So if virtiofsd starts without xattr support and somebody runs a >> > VM with SELinux enabled, they should still be able to mount virtiofs, >> > I guess (instead of failing it). >> >> SELinux requires that everything is always labeled one way or another >> and so if SELinux is enabled one should either use genfscon or fs_use xattr >> >> Since is support fs_use xattr that should be the default and if any >> would for any reason want to replace that with genfscon then that is >> something they have to address (by excluding the fs_use xattr rule and >> replacing it with a genfscon rule (not sure why anyone would ever want >> that) >> >> Gist is that if SELinux is enabled then one of the two should be >> present, preferably fs_use xattr (so thats the default). > > I understand that current state is that one needs to choose either > genfscon or fs_use_xattr depending on filesystem type. Will be nice > if this was more flexibile. > > If virtiofsd is running on top of a filesystem which does not support > xattr, then also virtiofs mount will fail. > > IOW, with virtiofs both kind of configurations can be easily produed > (xattr enabled or disabled). So none of the defaults (genfscon or > fs_use_xattr) seems to be ideal. > > IIUC, policy is assuming that virtiofs will either always support xattr > or will not always support xattrs. Which probably is true for many > filesystems. But not necessarily in this case. So hard coding one > assumption will break other configurations. It will be nice if we there > is a way to fix this in policy. Sorry I think I misunderstood the issue. James Carter's solution sounds like the way to go. Either that or just dont support fs_use xattr and always mount the whole location with a context specified from configuration (mount -t virtiofs -o context=). > > Thanks > Vivek > -- gpg --locate-keys dominick.grift@xxxxxxxxxxx Key fingerprint = FCD2 3660 5D6B 9D27 7FC6 E0FF DA7E 521F 10F6 4098 https://sks-keyservers.net/pks/lookup?op=get&search=0xDA7E521F10F64098 Dominick Grift
