Re: question about /proc/<PID>/mem in 2.4

[Tigran Aivazian]

On Tue, 6 Jul 2004, Marcelo Tosatti wrote:
> On Tue, Jul 06, 2004 at 12:14:04PM +0100, Tigran Aivazian wrote:
> > Ok, but still nobody seems to know why the super user is not allowed to
> > access /proc/<PID>/mem of any task. Any code which nobody in the world
> > knows the reason for, is broken and should be removed.
> > 
> > I will wait a few weeks to see if someone does come up with the reason for
> > that "extra secure" check in mem_read() and if nobody has objections I'll
> > send Linus a patch to relax the check to a more reasonable one, namely to
> > allow CAP_SYS_PTRACE process to bypass any other conditions imposed.
> 
> Hi Tigran, 
> 
> This code was added to stop the ptrace/kmod vulnerabilities. I do not 
> fully understand the issues around tsk->is_dumpable and the fix itself,
> but I agree on that the checks here could be relaxed for the super user.
> 
> However changing it to 
> 
>         if (!is_dumpable(task) && !capable(CAP_SYS_PTRACE))
>                 goto out;
> 
> Seems wrong because this will stop always honoring the tsk->is_dumpable flag. (?)
> 
> Alan for sure can make the picture clear - he wrote this thing.

Ok, let's see what Alan says then (if he has time to look at it).

Btw, the mem_read() code in both 2.4 and 2.6 can be cleaned up to use
get_task_mm() inline instead of doing it inline "manually".

Kind regards
Tigran


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