On Tue, Jun 01, 2010 at 07:55:02AM -0400, Eric Paris wrote: > On Tue, 2010-06-01 at 03:55 -0400, Christoph Hellwig wrote: > > On Mon, May 31, 2010 at 08:24:23PM -0700, Kees Cook wrote: > > > > My rationale is that if it's in commoncaps, it's effective for everyone, so > > > it might as well be in core VFS. If the VFS objections really do boil down > > > to "not in fs/" then I'm curious if doing this in commoncaps is acceptable. > > > > If you think the objection is about having things in fs/ you're smoking > > some really bad stuff. > > Sounds to me like we should probably follow the same path as > mmap_min_addr. We should add these hooks right in the VFS where they > belong (much like mmap_min_addr hooks into the vm) and control them 2 > ways. > > 1) a Kconfig so distros can choose to turn it on or off by default > 2) a /proc interface so root can turn it off > > Nothing about that precludes additional similar checks inside an LSM > (like CONFIG_LSM_MMAP_MIN_ADDR) which can be more finely controlled. So > maybe we want to follow up with the core VFS check with new checks in > SELinux (and maybe apparmour). This allows the user to disable the > general check and still be provided with some modicum of protection. > You might ask why not ONLY do the check in SELinux and drop the generic > check, but we have seen with mmap_min_addr that the SELinux unconfined > user can do damn well anything it wants to, so having a non-LSM version > of appropriate security checks is highly regarded. Would a CONFIG for this be overkill? mmap_min_addr is a little different in that there was desire to control a bottom limit on it, etc. Given this is either "on" or "off", I think just a sysctl is needed? I will send a v3 patch that fixes the sysctl name and default, so that it is up to the distro and end user how to configure their symlink semantics. -Kees -- Kees Cook Ubuntu Security Team -- 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
