Re: [PATCH 5/6] exec: Move handling of the point of no return to the top level

[Kees Cook]

On Fri, May 08, 2020 at 01:47:10PM -0500, Eric W. Biederman wrote:
> 
> Move the handing of the point of no return from search_binary_handler
> into __do_execve_file so that it is easier to find, and to keep
> things robust in the face of change.
> 
> Make it clear that an existing fatal signal will take precedence over
> a forced SIGSEGV by not forcing SIGSEGV if a fatal signal is already
> pending.  This does not change the behavior but it saves a reader
> of the code the tedium of reading and understanding force_sig
> and the signal delivery code.
> 
> Update the comment in begin_new_exec about where SIGSEGV is forced.
> 
> Keep point_of_no_return from being a mystery by documenting
> what the code is doing where it forces SIGSEGV if the
> code is past the point of no return.
> 
> Signed-off-by: "Eric W. Biederman" <ebiederm@xxxxxxxxxxxx>

I had to read the code around these changes a bit carefully, but yeah,
this looks like a safe cleanup. It is a behavioral change, though (in
that in unmasks non-SEGV fatal signals), so I do wonder if something
somewhere might notice this, but I'd agree that it's the more robust
behavior.

Reviewed-by: Kees Cook <keescook@xxxxxxxxxxxx>

-- 
Kees Cook