[v2,0/3] Relocate execve() sanity checks

Message

Kees Cook June 5, 2020, 4 p.m. UTC

Hi,

While looking at the code paths for the proposed O_MAYEXEC flag, I saw
some things that looked like they should be fixed up.

  exec: Change uselib(2) IS_SREG() failure to EACCES
	This just regularizes the return code on uselib(2).

  exec: Move S_ISREG() check earlier
	This moves the S_ISREG() check even earlier than it was already.

  exec: Move path_noexec() check earlier
	This adds the path_noexec() check to the same place as the
	S_ISREG() check.

v2:
- move checks into may_open() using acc_mode instead of f_mode to correctly
  compose with other inode file type tests[1].
- drop the FMODE_EXEC f_flags -> f_mode change for now since it remains
  unclear if it's useful (and is not needed any more for this series).
v1: https://lore.kernel.org/linux-api/[e-mail]/

Thanks!

-Kees

[1] https://lore.kernel.org/lkml/202006041910.9EF0C602@keescook/

Kees Cook (3):
  exec: Change uselib(2) IS_SREG() failure to EACCES
  exec: Move S_ISREG() check earlier
  exec: Move path_noexec() check earlier

 fs/exec.c  | 23 ++++++++++++++---------
 fs/namei.c | 10 ++++++++--
 fs/open.c  |  6 ------
 3 files changed, 22 insertions(+), 17 deletions(-)

Comments

Andrew Morton June 6, 2020, 12:40 a.m. UTC | #1

On Fri,  5 Jun 2020 09:00:10 -0700 Kees Cook <[e-mail]> wrote:

> While looking at the code paths for the proposed O_MAYEXEC flag, I saw
> some things that looked like they should be fixed up.
> 
>   exec: Change uselib(2) IS_SREG() failure to EACCES
> 	This just regularizes the return code on uselib(2).
> 
>   exec: Move S_ISREG() check earlier
> 	This moves the S_ISREG() check even earlier than it was already.
> 
>   exec: Move path_noexec() check earlier
> 	This adds the path_noexec() check to the same place as the
> 	S_ISREG() check.

Thanks.

These don't seem super-urgent and they aren't super-reviewed, so I
suggest we hold them off until the next cycle?

Kees Cook June 6, 2020, 1:45 a.m. UTC | #2

On Fri, Jun 05, 2020 at 05:40:53PM -0700, Andrew Morton wrote:
> On Fri,  5 Jun 2020 09:00:10 -0700 Kees Cook <[e-mail]> wrote:
> 
> > While looking at the code paths for the proposed O_MAYEXEC flag, I saw
> > some things that looked like they should be fixed up.
> > 
> >   exec: Change uselib(2) IS_SREG() failure to EACCES
> > 	This just regularizes the return code on uselib(2).
> > 
> >   exec: Move S_ISREG() check earlier
> > 	This moves the S_ISREG() check even earlier than it was already.
> > 
> >   exec: Move path_noexec() check earlier
> > 	This adds the path_noexec() check to the same place as the
> > 	S_ISREG() check.
> 
> Thanks.
> 
> These don't seem super-urgent and they aren't super-reviewed, so I
> suggest we hold them off until the next cycle?

Agreed; that's fine by me. It's mostly clean up and preparation for
performing future checking through the MAY_EXEC path.

And I'd love to get an Ack from Al or Aleksa, nudge nudge. :)