Messages in this thread | | | Subject | Re: [PATCH 4/4] pmap: reduced permissions | From | Arjan van de Ven <> | Date | Mon, 23 Jan 2006 10:41:45 +0100 |
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On Mon, 2006-01-23 at 04:28 -0500, Albert Cahalan wrote: > On 1/23/06, Arjan van de Ven <arjan@infradead.org> wrote: > > On Sun, 2006-01-22 at 17:19 -0500, Albert D. Cahalan wrote: > > > This patch changes all 3 remaining maps files to be readable > > > only for the file owner. There have been privacy concerns. > > > > > > Fedora Core 4 has been shipping with such permissions on > > > the /proc/*/maps file already. General system monitoring > > > tools seldom use these files. > > > > changing /maps to 0400 breaks glibc; there are cases where this would > > lead to /proc/self/maps to be not readable (setuid like apps) so this > > needs a more elaborate fix. > > Wow. Well, that's why I put the patch last in the series. > The other 3 don't depend on it at all. > > I tend to think that glibc should not be reading this file. > What excuse is there?
glibc needs to be able to find out if a certain address is writable. (eg mapped "w"). The only way available for that is... reading the maps file.
> In any case, the many existing statically linked executables > do cause trouble. Setuid apps are the ones you'd most want > to protect.
for this 0400 isn't enough; because you can open this file, send the fd over a unix socket, and then exec. The process you sent the fd to can then read the setuid's program maps file.
This thing is all a bit more complex than just the file mode ;(
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