Andi Kleen <andi@xxxxxxxxxxxxxx> writes: > Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> writes: > >> On Fri, 20 Apr 2007 12:25:39 +0200 Miklos Szeredi <miklos@xxxxxxxxxx> wrote: >> >> > Define a new fs flag FS_SAFE, which denotes, that unprivileged >> > mounting of this filesystem may not constitute a security problem. >> > >> > Since most filesystems haven't been designed with unprivileged >> > mounting in mind, a thorough audit is needed before setting this flag. >> >> Practically speaking, is there any realistic likelihood that any filesystem >> apart from FUSE will ever use this? > > If it worked for mount --bind for any fs I could see uses of this. I haven't > thought > through the security implications though, so it might not work. Binding a directory that you have access to in other was is essentially the same thing as a symlink. So there are no real security implications there. The only problem case I can think of is removal media that you want to remove but someone has made a bind mount to. But that is essentially the same case as opening a file so there are no new real issues. Although our diagnostic tools will likely fall behind for a bit. We handle the security implications by assigning an owner to all mounts and only allowing you to add additional mounts on top of a mount you already own. If you have the right capabilities you can create a mount owned by another user. For a new mount if you don't have the appropriate capabilities nodev and nosuid will be forced. Initial super block creation is a lot more delicate so we need the FS_SAFE flag, to know that the kernel is prepared to deal with the crazy things that a hostile user space is prepared to do. Eric - 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
