Re: [PATCH] proc: Enable smaps_rollup without ptrace rights

[Andrew Morton]

On Thu, 8 Sep 2022 11:39:19 +0200 Vincent Whitchurch <vincent.whitchurch@xxxxxxxx> wrote:

> smaps_rollup is currently only allowed on processes which the user has
> ptrace permissions for, since it uses a common proc open function used
> by other files like mem and smaps.
> 
> However, while smaps provides detailed, individual information about
> each memory map in the process (justifying its ptrace rights
> requirement), smaps_rollup only provides a summary of the memory usage,
> which is not unlike the information available from other places like the
> status and statm files, which do not need ptrace permissions.
> 
> The first line of smaps_rollup could however be sensitive, since it
> exposes the randomized start and end of the process' address space.
> This information however does not seem essential to smap_rollup's
> purpose and could be replaced with placeholder values to preserve the
> format without leaking information.  (I could not find any user space in
> Debian or Android which uses the information in the first line.)
> 
> Replace the start with 0 and end with ~0 and allow smaps_rollup to be
> opened and read regardless of ptrace permissions.

What is the motivation for this?  Use case?  End-user value and such?