On Fri, May 11, 2012 at 09:25:37AM -0500, Rob Landley wrote: > Well it's certainly a point of view. Luckily, FAT already _has_ the > workaround we're discussing. The objections were mainly "can't the VFS > do this for us?" and the answer, upon closer inspection, turned out to > be "not easily, no, the VFS takes option flags instead of parsing string > options so doesn't have some necessary infrastructure". The only reasonable use case I can imagine for this feature is one where someone wants to use a removable storage device (which could be a USB thumb drive to a USB HDD to a SSD in a USB 3.0 enclosure) as an interchange device between Unix systems which do not have compatible uid/gid spaces. So perhaps the right approach is that we should have an ext2/3/4 read-only feature flag which enforces a default of nosuid and all files to be read-only and world-readable. There would be mount options which could modify this default behaviour so that the files could be writeable by a particular uid or gid, and another mount option which would change the permission bits seen for that file system from 0755/0644 for directories/files to 0700/0600. Basically, the idea is we should mark the file system in an explicit way that it is intended for interchange across incompatible uid/gid spaces, with defaults which minimize security risk. The fact that all files become world-readable is potentially a risk, but if the user is willing to put their private files on a removeable media that could easily be dropped in a parking lot, or otherwise stolen or lost, that's a potential risk that they've implicitly accepted in any case; we might as well make it be explicit. - Ted -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
