linux-kernel - [PATCH v2 7/8] exec: Consolidate pdeath

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Date:   Mon, 10 Jul 2017 00:57:30 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     Kees Cook <keescook@...omium.org>,
        Andy Lutomirski <luto@...nel.org>,
        David Howells <dhowells@...hat.com>,
        Serge Hallyn <serge@...lyn.com>,
        John Johansen <john.johansen@...onical.com>,
        Casey Schaufler <casey@...aufler-ca.com>,
        "Eric W. Biederman" <ebiederm@...ssion.com>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Michal Hocko <mhocko@...nel.org>,
        Ben Hutchings <ben@...adent.org.uk>,
        Hugh Dickins <hughd@...gle.com>,
        Oleg Nesterov <oleg@...hat.com>,
        "Jason A. Donenfeld" <Jason@...c4.com>,
        Rik van Riel <riel@...hat.com>,
        James Morris <james.l.morris@...cle.com>,
        Greg Ungerer <gerg@...ux-m68k.org>,
        Ingo Molnar <mingo@...nel.org>,
        Nicolas Pitre <nicolas.pitre@...aro.org>,
        Stephen Smalley <sds@...ho.nsa.gov>,
        Paul Moore <paul@...l-moore.com>,
        Vivek Goyal <vgoyal@...hat.com>,
        Mickaël Salaün <mic@...ikod.net>,
        Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>,
        linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-security-module@...r.kernel.org, selinux@...ho.nsa.gov
Subject: [PATCH v2 7/8] exec: Consolidate pdeath_signal clearing

Instead of an additional secureexec check for pdeath_signal, just move it
up into the initial secureexec test. Neither perf nor arch code touches
pdeath_signal, so the relocation shouldn't change anything.

Signed-off-by: Kees Cook <keescook@...omium.org>
---
 fs/exec.c | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/fs/exec.c b/fs/exec.c
index eeb8323977d1..e0186db02f90 100644
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -1340,6 +1340,9 @@ void setup_new_exec(struct linux_binprm * bprm)
 	if (security_bprm_secureexec(bprm)) {
 		/* Record for AT_SECURE. */
 		bprm->secureexec = 1;
+
+		/* Make sure parent cannot signal privileged process. */
+		current->pdeath_signal = 0;
 	}
 
 	arch_pick_mmap_layout(current->mm);
@@ -1363,10 +1366,6 @@ void setup_new_exec(struct linux_binprm * bprm)
 	 */
 	current->mm->task_size = TASK_SIZE;
 
-	if (bprm->secureexec) {
-		current->pdeath_signal = 0;
-	}
-
 	/* An exec changes our domain. We are no longer part of the thread
 	   group */
 	current->self_exec_id++;
-- 
2.7.4