linux-kernel - [PATCH v5 29/38] Smack: Abstract use of file security blob

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Message-ID: <a158e14c-c75c-8f84-a131-aa1ba209a4d9@schaufler-ca.com>
Date:   Mon, 26 Nov 2018 15:49:23 -0800
From:   Casey Schaufler <casey@...aufler-ca.com>
To:     James Morris <jmorris@...ei.org>,
        LSM <linux-security-module@...r.kernel.org>,
        LKLM <linux-kernel@...r.kernel.org>,
        SE Linux <selinux@...ho.nsa.gov>
Cc:     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>,
        "linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>,
        Stephen Smalley <sds@...ho.nsa.gov>,
        Alexey Dobriyan <adobriyan@...il.com>,
        Mickaël Salaün <mic@...ikod.net>,
        Salvatore Mesoraca <s.mesoraca16@...il.com>
Subject: [PATCH v5 29/38] Smack: Abstract use of file security blob

Don't use the file->f_security pointer directly.
Provide a helper function that provides the security blob pointer.

Signed-off-by: Casey Schaufler <casey@...aufler-ca.com>
Reviewed-by: Kees Cook <keescook@...omium.org>
Signed-off-by: Kees Cook <keescook@...omium.org>
---
 security/smack/smack.h     |  5 +++++
 security/smack/smack_lsm.c | 12 ++++++++----
 2 files changed, 13 insertions(+), 4 deletions(-)

diff --git a/security/smack/smack.h b/security/smack/smack.h
index b27eb252e953..50854969a391 100644
--- a/security/smack/smack.h
+++ b/security/smack/smack.h
@@ -362,6 +362,11 @@ static inline struct task_smack *smack_cred(const struct cred *cred)
 	return cred->security + smack_blob_sizes.lbs_cred;
 }
 
+static inline struct smack_known **smack_file(const struct file *file)
+{
+	return (struct smack_known **)&file->f_security;
+}
+
 /*
  * Is the directory transmuting?
  */
diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c
index 459f7d523ca6..3e11be8cce7e 100644
--- a/security/smack/smack_lsm.c
+++ b/security/smack/smack_lsm.c
@@ -1573,9 +1573,9 @@ static void smack_inode_getsecid(struct inode *inode, u32 *secid)
  */
 static int smack_file_alloc_security(struct file *file)
 {
-	struct smack_known *skp = smk_of_current();
+	struct smack_known **blob = smack_file(file);
 
-	file->f_security = skp;
+	*blob = smk_of_current();
 	return 0;
 }
 
@@ -1815,7 +1815,9 @@ static int smack_mmap_file(struct file *file,
  */
 static void smack_file_set_fowner(struct file *file)
 {
-	file->f_security = smk_of_current();
+	struct smack_known **blob = smack_file(file);
+
+	*blob = smk_of_current();
 }
 
 /**
@@ -1832,6 +1834,7 @@ static void smack_file_set_fowner(struct file *file)
 static int smack_file_send_sigiotask(struct task_struct *tsk,
 				     struct fown_struct *fown, int signum)
 {
+	struct smack_known **blob;
 	struct smack_known *skp;
 	struct smack_known *tkp = smk_of_task(smack_cred(tsk->cred));
 	const struct cred *tcred;
@@ -1845,7 +1848,8 @@ static int smack_file_send_sigiotask(struct task_struct *tsk,
 	file = container_of(fown, struct file, f_owner);
 
 	/* we don't log here as rc can be overriden */
-	skp = file->f_security;
+	blob = smack_file(file);
+	skp = *blob;
 	rc = smk_access(skp, tkp, MAY_DELIVER, NULL);
 	rc = smk_bu_note("sigiotask", skp, tkp, MAY_DELIVER, rc);
 
-- 
2.14.5