[PATCH RFC v3 6/7] proc: support new 'pids=all|ptraceable' mount option

On Thu, 9 Nov 2017, Djalal Harouni wrote:

This patch introduces the new 'pids' mount option, as it was discussed
and suggested by Andy Lutomirski [1].

* If 'pids=' is passed without 'newinstance' then it has no effect.

* If 'newinstance,pids=all' then all processes will be shown in proc.

* If 'newinstance,pids=ptraceable' then only ptraceable processes will be
shown.

* 'pids=' takes precendence over 'hidepid=' since 'hidepid=' can be
  ignored if "gid=" was set and caller has the "gid=" set in its groups.
  We want to guarantee that LSM have a security path there that can not
  be disabled with "gid=".

This allows to support lightweight sandboxes in Embedded Linux.

Later Yama LSM can be updated to check that processes are able only
able to see their children inside /proc/, allowing to support more tight
cases.

[1] https://lkml.org/lkml/2017/4/26/646

Cc: Kees Cook <redacted>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Suggested-by: Andy Lutomirski <luto@kernel.org>
Signed-off-by: Alexey Gladkov <redacted>
Signed-off-by: Djalal Harouni <redacted>

Reviewed-by: James Morris <redacted>


-- 
James Morris
[off-list ref]

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