linux-kernel - [PATCH v5 23/38] SELinux: Remove cred security blob poisoning

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Message-Id: <20181211224314.22412-24-casey@schaufler-ca.com>
Date:   Tue, 11 Dec 2018 14:42:59 -0800
From:   Casey Schaufler <casey@...aufler-ca.com>
To:     jmorris@...ei.org, linux-security-module@...r.kernel.org,
        linux-kernel@...r.kernel.org, selinux@...r.kernel.org
Cc:     john.johansen@...onical.com, keescook@...omium.org,
        penguin-kernel@...ove.sakura.ne.jp, paul@...l-moore.com,
        linux-fsdevel@...r.kernel.org, sds@...ho.nsa.gov,
        adobriyan@...il.com, mic@...ikod.net, s.mesoraca16@...il.com,
        casey@...aufler-ca.com
Subject: [PATCH v5 23/38] SELinux: Remove cred security blob poisoning

The SELinux specific credential poisioning only makes sense
if SELinux is managing the credentials. As the intent of this
patch set is to move the blob management out of the modules
and into the infrastructure, the SELinux specific code has
to go. The poisioning could be introduced into the infrastructure
at some later date.

Signed-off-by: Casey Schaufler <casey@...aufler-ca.com>
Reviewed-by: Kees Cook <keescook@...omium.org>
Signed-off-by: Kees Cook <keescook@...omium.org>
---
 kernel/cred.c            | 13 -------------
 security/selinux/hooks.c |  6 ------
 2 files changed, 19 deletions(-)

diff --git a/kernel/cred.c b/kernel/cred.c
index ecf03657e71c..fa2061ee4955 100644
--- a/kernel/cred.c
+++ b/kernel/cred.c
@@ -704,19 +704,6 @@ bool creds_are_invalid(const struct cred *cred)
 {
 	if (cred->magic != CRED_MAGIC)
 		return true;
-#ifdef CONFIG_SECURITY_SELINUX
-	/*
-	 * cred->security == NULL if security_cred_alloc_blank() or
-	 * security_prepare_creds() returned an error.
-	 */
-	if (selinux_is_enabled() && cred->security) {
-		if ((unsigned long) cred->security < PAGE_SIZE)
-			return true;
-		if ((*(u32 *)cred->security & 0xffffff00) ==
-		    (POISON_FREE << 24 | POISON_FREE << 16 | POISON_FREE << 8))
-			return true;
-	}
-#endif
 	return false;
 }
 EXPORT_SYMBOL(creds_are_invalid);
diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index 24b6b459fa2a..41b230d459a6 100644
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -3922,12 +3922,6 @@ static void selinux_cred_free(struct cred *cred)
 {
 	struct task_security_struct *tsec = selinux_cred(cred);
 
-	/*
-	 * cred->security == NULL if security_cred_alloc_blank() or
-	 * security_prepare_creds() returned an error.
-	 */
-	BUG_ON(cred->security && (unsigned long) cred->security < PAGE_SIZE);
-	cred->security = (void *) 0x7UL;
 	kfree(tsec);
 }
 
-- 
2.14.5