Re: [PATCH] Document how capability bits work

[Andy Lutomirski]

On Fri, Dec 7, 2012 at 11:21 AM, Serge Hallyn
<serge.hallyn@xxxxxxxxxxxxx> wrote:
> Quoting Andy Lutomirski (luto@xxxxxxxxxxxxxx):
>> Signed-off-by: Andy Lutomirski <luto@xxxxxxxxxxxxxx>
>> ---
>>  Documentation/security/capabilities.txt | 161 ++++++++++++++++++++++++++++++++
>>  1 file changed, 161 insertions(+)
>>  create mode 100644 Documentation/security/capabilities.txt
>
> TBH, I think a pointer to the capabilities.7 man page would be better.
> (plus, if you feel they are needed, updates to the man page)

Updating capabilities.7 wouldn't be a bad idea, but IMO it certainly
needs work.  For example, it says:

       Inheritable:
              This is a set of capabilities preserved across an execve(2).  It
              provides a mechanism for a process to assign capabilities to the
              permitted set of the new program during an execve(2).

This is, at best, misleading.

Permitted says:

              If  a  thread  drops a capability from its permitted set, it can
              never reacquire that capability (unless it execve(2)s  either  a
              set-user-ID-root  program,  or  a  program whose associated file
              capabilities grant that capability).

That's just not true (e.g. if uid == 0).

The text later on is better, but I think it would be helpful to have a
detailed and succinct description of what's going on.

I would be happy to revise this patch to reference capabilities.7.

--Andy
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