Re: Re: [PATCH] subsystem: pr??oc filesystem

[Al Viro]

On Sun, Dec 16, 2012 at 04:02:03PM +0400, tux2002@xxxxxxxx wrote:
> Not, this permissions saved for all users for later, check please.

... and that's why it's bogus.  umask of whoever had done lookup for
/proc/<something> affects everybody else.  For as long as the thing stays
in dcache.  At which point it's up for grabs (in that sense) again.
Do (umask 777; ls -l /proc) with your kernel and watch the results.
Note that you don't need to be root to cause that - anyone can do it.

Realize that dentries and inodes in /proc/<pid>/* are created on demand
whenever somebody does a lookup.  So running ps(1) suddenly makes you
a creator of a bunch of those.  Unless somebody else had done ps(1) (or
ls -l /proc, or...) first.  Basing any security decisions on _that_ is
insane.
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/