linux-kernel - Re: [PATCH] proc: do not show VmExe bigger than total executable virtual memory

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Date:   Tue, 10 Oct 2017 15:25:04 -0700
From:   Andrew Morton <akpm@...ux-foundation.org>
To:     Konstantin Khlebnikov <khlebnikov@...dex-team.ru>
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] proc: do not show VmExe bigger than total executable
 virtual memory

On Fri, 06 Oct 2017 14:32:34 +0300 Konstantin Khlebnikov <khlebnikov@...dex-team.ru> wrote:

> If start_code / end_code pointers are screwed then "VmExe" could be bigger
> than total executable virtual memory and "VmLib" becomes negative:
> 
> VmExe:	  294320 kB
> VmLib:	18446744073709327564 kB
> 
> VmExe and VmLib documented as text segment and shared library code size.
> 
> Now their sum will be always equal to mm->exec_vm which sums size of
> executable and not writable and not stack areas.

When does this happen?  What causes start_code/end_code to get "screwed"?

When these pointers are screwed, the result of end_code-start_code can
still be wrong while not necessarily being negative, yes?  In which
case we'll still display incorrect output?