On Fri, 29 Jun 2007, Andy Isaacson wrote: > On Thu, Jun 28, 2007 at 10:57:00PM -0400, Kyle Moffett wrote: > > On Jun 28, 2007, at 14:49:24, Davide Libenzi wrote: > > >So I implemented a rather quick hack that introduces a new mmap() > > >flag MAP_NOZERO (only valid for anonymous mappings) and the vma > > >counter-part VM_NOZERO. Also, a new sys_brk2() has been introduced > > >to accept a new flags parameter. A brief description of the > > >patches follows in the next emails. > > > > Hmm, sounds like this would also need a "MAP_NOREUSE" flag of some > > kind for security sensitive applications. Basically, I wouldn't want > > my ssh-agent pages holding private SSH keys to be reused by my web > > browser which then gets exploited :-D. > > PGP at least (and I think GPG still) did overwrite keys before calling > free(), and attempted to use mlock(). Looks like ssh-agent doesn't use > mlock -- at least it hasn't in this case: > % grep Lck /proc/`pidof ssh-agent`/status > VmLck: 0 kB > % ulimit -a | grep lock > file size (blocks) unlimited > core file size (blocks) 0 > locked-in-memory size (kb) 32 > file locks unlimited > > Requiring security-sensitive apps to use a new flag to get safe behavior > is dangerous. Better to be safe by default and turn on the > less-safe-but-faster behavior for the cases that benefit from it.
Can you better explain what MAP_NOZERO would alter in such case? > I still think that using uid in mm_struct is wrong, and some kind of > abstraction is required. I called this "free pool" in > <[EMAIL PROTECTED]>, but I think that name is > misleading -- I am not proposing that this should be part of the > management of free pages, but should be a label which abstracts "safe to > share freed pages among" groups. Then different SELinux protection > domains would simply have different labels. I think I answered this one at least a couple of times, but anyawy. First, that can be whatever cookie we choose. At the moment UID is used because it makes easier a fit into _mapcount. Second, SeLinux will be able to disable the feature on a per-process base, or globally. Anything else? - Davide - 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/
