linux-kernel - [PATCH v4 15/15] exec: Consolidate pdeath

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Date:   Mon, 31 Jul 2017 16:51:33 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     Kees Cook <keescook@...omium.org>,
        David Howells <dhowells@...hat.com>,
        "Eric W. Biederman" <ebiederm@...ssion.com>,
        John Johansen <john.johansen@...onical.com>,
        "Serge E. Hallyn" <serge@...lyn.com>,
        Paul Moore <paul@...l-moore.com>,
        Stephen Smalley <sds@...ho.nsa.gov>,
        Casey Schaufler <casey@...aufler-ca.com>,
        Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>,
        James Morris <james.l.morris@...cle.com>,
        Andy Lutomirski <luto@...nel.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        linux-fsdevel@...r.kernel.org,
        linux-security-module@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH v4 15/15] 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>
Acked-by: Serge Hallyn <serge@...lyn.com>
---
 fs/exec.c | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/fs/exec.c b/fs/exec.c
index cddd2a2cbc1f..5a19912a4f53 100644
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -1330,6 +1330,9 @@ void setup_new_exec(struct linux_binprm * bprm)
 	bprm->secureexec |= bprm->cap_elevated;
 
 	if (bprm->secureexec) {
+		/* Make sure parent cannot signal privileged process. */
+		current->pdeath_signal = 0;
+
 		/*
 		 * For secureexec, reset the stack limit to sane default to
 		 * avoid bad behavior from the prior rlimits. This has to
@@ -1362,10 +1365,6 @@ 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