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

[Casey Schaufler]

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

Signed-off-by: Casey Schaufler <ca...@schaufler-ca.com>
Reviewed-by: Kees Cook <keesc...@chromium.org>
Signed-off-by: Kees Cook <keesc...@chromium.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


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