linux-kernel - [PATCH v4 20/19] LSM: Correct file blob free empty blob check

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Date:   Wed, 26 Sep 2018 14:57:03 -0700
From:   Casey Schaufler <casey@...aufler-ca.com>
To:     LSM <linux-security-module@...r.kernel.org>,
        James Morris <jmorris@...ei.org>,
        SE Linux <selinux@...ho.nsa.gov>,
        LKLM <linux-kernel@...r.kernel.org>,
        John Johansen <john.johansen@...onical.com>,
        Kees Cook <keescook@...omium.org>,
        Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>,
        Paul Moore <paul@...l-moore.com>,
        Stephen Smalley <sds@...ho.nsa.gov>,
        "linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>,
        Alexey Dobriyan <adobriyan@...il.com>,
        Mickaël Salaün <mic@...ikod.net>,
        Salvatore Mesoraca <s.mesoraca16@...il.com>
Subject: [PATCH v4 20/19] LSM: Correct file blob free empty blob check

Instead of checking if the kmem_cache for file blobs
has been initialized check if the blob is NULL. This
allows non-blob using modules to do other kinds of
clean up in the security_file_free hooks.

Signed-off-by: Casey Schaufler <casey@...aufler-ca.com>
---
 security/security.c | 9 ++++-----
 1 file changed, 4 insertions(+), 5 deletions(-)

diff --git a/security/security.c b/security/security.c
index e7c8506041f1..76f7dc49b63c 100644
--- a/security/security.c
+++ b/security/security.c
@@ -1202,14 +1202,13 @@ void security_file_free(struct file *file)
 {
 	void *blob;
 
-	if (!lsm_file_cache)
-		return;
-
 	call_void_hook(file_free_security, file);
 
 	blob = file->f_security;
-	file->f_security = NULL;
-	kmem_cache_free(lsm_file_cache, blob);
+	if (blob) {
+		file->f_security = NULL;
+		kmem_cache_free(lsm_file_cache, blob);
+	}
 }
 
 int security_file_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
-- 
2.17.1