Re: [PATCH] exec: Weaken dumpability for secureexec

Serge E. Hallyn
2018-01-03T07:04:47Z

On Tue, Jan 02, 2018 at 03:21:33PM -0800, Kees Cook wrote:
> This is a logical revert of:
>
> commit e37fdb785a5f ("exec: Use secureexec for setting dumpability")
>
> This weakens dumpability back to checking only for uid/gid changes in
> current (which is useless), but userspace depends on dumpability not
> being tied to secureexec.
>
> https://bugzilla.redhat.com/show_bug.cgi?id=1528633
>
> Reported-by: Tom Horsley <horsley1953@gmail.com>

Seems right, any chance we could get a tested-by: Tom? (Did we already
get that?)

> Fixes: e37fdb785a5f ("exec: Use secureexec for setting dumpability")
> Cc: stable@vger.kernel.org
> Signed-off-by: Kees Cook <keescook@chromium.org>
> ---
> fs/exec.c | 9 +++++++--
> 1 file changed, 7 insertions(+), 2 deletions(-)
>
> diff --git a/fs/exec.c b/fs/exec.c
> index 5688b5e1b937..7eb8d21bcab9 100644
> --- a/fs/exec.c
> +++ b/fs/exec.c
> @@ -1349,9 +1349,14 @@ void setup_new_exec(struct linux_binprm * bprm)
>
> current->sas_ss_sp = current->sas_ss_size = 0;
>
> - /* Figure out dumpability. */
> + /*
> + * Figure out dumpability. Note that this checking only of current
> + * is wrong, but userspace depends on it. This should be testing
> + * bprm->secureexec instead.
> + */
> if (bprm->interp_flags & BINPRM_FLAGS_ENFORCE_NONDUMP ||
> - bprm->secureexec)
> + !(uid_eq(current_euid(), current_uid()) &&
> + gid_eq(current_egid(), current_gid())))
> set_dumpable(current->mm, suid_dumpable);
> else
> set_dumpable(current->mm, SUID_DUMP_USER);
> --
> 2.7.4
>
>
> --
> Kees Cook
> Pixel Security