Re: [RFC][PATCH v2] procfs: Always expose /proc/<pid>/map_files/ and make it readable

On Mon, Jan 26, 2015 at 10:50:23PM -0800, Andrew Morton wrote:

On Tue, 27 Jan 2015 09:46:47 +0300 Cyrill Gorcunov [off-list ref] wrote:

quoted

quoted

There's one other problem here: we're assuming that the map_files
implementation doesn't have bugs.  If it does have bugs then relaxing
permissions like this will create new vulnerabilities.  And the
map_files implementation is surprisingly complex.  Is it bug-free?

I didn't find any bugs in map-files (and we use it for long time already)
so I think it is safe.

You've been using map_files the way it was supposed to be used so no,
any bugs won't show up.  What happens if you don your evil black hat
and use map_files in ways that weren't anticipated?  Attack it?

Hard to say, Andrew. If I found a way to exploit this feature for
bad purpose for sure I would patch it out. At the moment I don't
see any. Touching another process memory via file descriptor
allows one to modify its contents but you have to be granted
ptrace-may-access which i consider as enough for security.