Messages in this thread | | | Date | Sun, 6 May 2007 12:21:51 +0200 | From | Frank van Maarseveen <> | Subject | Re: unprivileged mount problems: device permissions ignored, mount sharing |
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On Wed, May 02, 2007 at 09:56:52AM +0200, Miklos Szeredi wrote: > > I tried the unprivileged mount v5 patches with 2.6.21.1. I made some > > experiments with normal filesystems (ext3, xfs, iso9660). I removed the > > FS_SAFE checks for that. > > Thanks for looking at this. > > > Mounting and umounting as unprivileged user (user1) works, e.g. > > (/mnt/user1 is a mount owned by user1) > > > > [user1@segv ~]$ mmount -t xfs /dev/mapper/vg00-test /mnt/user1 > > > > But the device permissions are ignored. The unprivileged user can mount > > the block device even there are no permissions to access it: > > > > brw------- 1 root root 253, 5 Apr 29 18:32 /dev/mapper/vg00-test > > Yes, I'm aware of this. Before we enable FS_SAFE for block > filesystems, this must be addressed. > > But I'm not sure _if_ we'll ever want this. It is very likely that > there are some other security holes in most filesystems that are > difficult to address. One example is checking for hard-linked > directories, which is normally only done during an fsck.
Some filesystems are not hardened against mounting a corrupted image and can Oops. This is also a problem for automounting USB sticks except that in that case you're (probably) sitting next to the hardware so there are other ways to do bad things.
From a security point of view I'd like to restrict unprivileged mounts to a configurable list of filesystem types.
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