[PATCH 0/2] exec: Use sane stack rlimit for setuid exec

Kees Cook keescook at chromium.org
Sat Jul 8 03:59:32 UTC 2017

On Fri, Jul 7, 2017 at 1:04 PM, Linus Torvalds
<torvalds at linux-foundation.org> wrote:
> On Fri, Jul 7, 2017 at 12:56 PM, Kees Cook <keescook at chromium.org> wrote:
>> As discussed with Linus and Andy, we need to reset the stack rlimit
>> before we do memory layouts when execing a privilege-gaining (e.g.
>> setuid) program. This moves security_bprm_secureexec() earlier (with
>> required changes), and then lowers the stack limit when appropriate.
> Looks sane to me, and that first patch looks like a nice cleanup
> regardless - the old semantics were insane.
> But yes, we should have more people look at this, particular have the
> security module people look at that first patch to make sure it is the
> right thing to do for their policies, and make sure that everybody's
> bprm_secureexec() function actually looks at the creds in the brmp,
> not "current" (well, maybe they compare the two, which makes tons of
> sense, and which the old  placement didn't sanely support).
> It looks like Kees went through the security modules, but having the
> people involved double-check is a good good idea.

Updated tree here, I'll send the series in email on Monday:

This should fix the missed bprm->cred->security and breaks out each
step into logical pieces in case we need to sanely bisect.


Kees Cook
Pixel Security
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