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

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Date:   Tue, 11 Dec 2018 14:43:05 -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 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