Stephen Smalley <[email protected]> wrote:
> > I was also wondering if I could generalise it to handle all cache types,
> > but the permissions checks are probably going to be quite different for
> > each type. For instance, CacheFiles uses files on a mounted fs, whilst
> > CacheFS uses a block device.
>
> So in the latter case, the daemon supplies the path of a block device
> node?
No. In the latter case, there is no userspace daemon. As there are no
dentries, filenames and paths in CacheFS, keeping track of the cull table
consumes a less space than for CacheFiles.
You start the cache by mounting it:
mount -t cachefs /dev/hdx9 /cachefs
Then it's online. However, you might want to check that whoever's calling
mount has permission to bring a cache online...
Actually, I think the permission to bring a cache online applies in all cases,
and is probably separate from checking that CacheFiles(d) is permitted to
mangle the filesystem it's using for a cache. With CacheFS, we could do the
equivalent and do a MAC check to make sure we're permitted to read and write
the blockdev, as you suggest in the next bit:
> I suppose the hook could internally check the type of inode to decide what
> checks to apply, using the checks I previously sketched when it is a
> directory and using a different set of checks for the block device
> (substituting a write check against the block device for the
> directory-specific checks). The hook interface itself would look the same
> IIUC, i.e. providing the (mnt, dentry) pair to which the path resolved and
> the secid to which the context resolved.
So, to summarise, is it worth having two checks:
(1) Permission to bring a cache online or to take a cache offline.
(2) Permission for the process bringing the cache online (cachefilesd or
mount) to access the backing store, be it a set of files and directories,
or be it a blockdev.
David
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to [email protected]
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
[Index of Archives]
[Kernel Newbies]
[Netfilter]
[Bugtraq]
[Photo]
[Stuff]
[Gimp]
[Yosemite News]
[MIPS Linux]
[ARM Linux]
[Linux Security]
[Linux RAID]
[Video 4 Linux]
[Linux for the blind]
[Linux Resources]
