LSM: Infrastructure management of the inode security

Move management of the inode->i_security blob out
of the individual security modules and into the security
infrastructure. Instead of allocating the blobs from within
the modules the modules tell the infrastructure how much
space is required, and the space is allocated there.

Signed-off-by: Casey Schaufler <casey@schaufler-ca.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
[kees: adjusted for ordered init series]
Signed-off-by: Kees Cook <keescook@chromium.org>

2 files changed, 18 insertions, 60 deletions

diff --git a/security/smack/smack.h b/security/smack/smack.h
index 436231dfae33..bf0abc35ca1c 100644
--- a/security/smack/smack.h
+++ b/security/smack/smack.h
@@ -370,7 +370,7 @@ static inline struct smack_known **smack_file(const struct file *file)
 
 static inline struct inode_smack *smack_inode(const struct inode *inode)
 {
-	return inode->i_security;
+	return inode->i_security + smack_blob_sizes.lbs_inode;
 }
 
 /*
diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c
index ddffda39d107..804897c82810 100644
--- a/security/smack/smack_lsm.c
+++ b/security/smack/smack_lsm.c
@@ -305,24 +305,18 @@ static struct smack_known *smk_fetch(const char *name, struct inode *ip,
 }
 
 /**
- * new_inode_smack - allocate an inode security blob
+ * init_inode_smack - initialize an inode security blob
+ * @isp: the blob to initialize
  * @skp: a pointer to the Smack label entry to use in the blob
  *
- * Returns the new blob or NULL if there's no memory available
  */
-static struct inode_smack *new_inode_smack(struct smack_known *skp)
+static void init_inode_smack(struct inode *inode, struct smack_known *skp)
 {
-	struct inode_smack *isp;
-
-	isp = kmem_cache_zalloc(smack_inode_cache, GFP_NOFS);
-	if (isp == NULL)
-		return NULL;
+	struct inode_smack *isp = smack_inode(inode);
 
 	isp->smk_inode = skp;
 	isp->smk_flags = 0;
 	mutex_init(&isp->smk_lock);
-
-	return isp;
 }
 
 /**
@@ -709,6 +703,13 @@ static int smack_set_mnt_opts(struct super_block *sb,
 	if (sp->smk_flags & SMK_SB_INITIALIZED)
 		return 0;
 
+	if (inode->i_security == NULL) {
+		int rc = lsm_inode_alloc(inode);
+
+		if (rc)
+			return rc;
+	}
+
 	if (!smack_privileged(CAP_MAC_ADMIN)) {
 		/*
 		 * Unprivileged mounts don't get to specify Smack values.
@@ -773,17 +774,12 @@ static int smack_set_mnt_opts(struct super_block *sb,
 	/*
 	 * Initialize the root inode.
 	 */
-	isp = smack_inode(inode);
-	if (isp == NULL) {
-		isp = new_inode_smack(sp->smk_root);
-		if (isp == NULL)
-			return -ENOMEM;
-		inode->i_security = isp;
-	} else
-		isp->smk_inode = sp->smk_root;
+	init_inode_smack(inode, sp->smk_root);
 
-	if (transmute)
+	if (transmute) {
+		isp = smack_inode(inode);
 		isp->smk_flags |= SMK_INODE_TRANSMUTE;
+	}
 
 	return 0;
 }
@@ -881,49 +877,11 @@ static int smack_inode_alloc_security(struct inode *inode)
 {
 	struct smack_known *skp = smk_of_current();
 
-	inode->i_security = new_inode_smack(skp);
-	if (inode->i_security == NULL)
-		return -ENOMEM;
+	init_inode_smack(inode, skp);
 	return 0;
 }
 
 /**
- * smack_inode_free_rcu - Free inode_smack blob from cache
- * @head: the rcu_head for getting inode_smack pointer
- *
- *  Call back function called from call_rcu() to free
- *  the i_security blob pointer in inode
- */
-static void smack_inode_free_rcu(struct rcu_head *head)
-{
-	struct inode_smack *issp;
-
-	issp = container_of(head, struct inode_smack, smk_rcu);
-	kmem_cache_free(smack_inode_cache, issp);
-}
-
-/**
- * smack_inode_free_security - free an inode blob using call_rcu()
- * @inode: the inode with a blob
- *
- * Clears the blob pointer in inode using RCU
- */
-static void smack_inode_free_security(struct inode *inode)
-{
-	struct inode_smack *issp = smack_inode(inode);
-
-	/*
-	 * The inode may still be referenced in a path walk and
-	 * a call to smack_inode_permission() can be made
-	 * after smack_inode_free_security() is called.
-	 * To avoid race condition free the i_security via RCU
-	 * and leave the current inode->i_security pointer intact.
-	 * The inode will be freed after the RCU grace period too.
-	 */
-	call_rcu(&issp->smk_rcu, smack_inode_free_rcu);
-}
-
-/**
  * smack_inode_init_security - copy out the smack from an inode
  * @inode: the newly created inode
  * @dir: containing directory object
@@ -4548,6 +4506,7 @@ static int smack_dentry_create_files_as(struct dentry *dentry, int mode,
 struct lsm_blob_sizes smack_blob_sizes __lsm_ro_after_init = {
 	.lbs_cred = sizeof(struct task_smack),
 	.lbs_file = sizeof(struct smack_known *),
+	.lbs_inode = sizeof(struct inode_smack),
 };
 
 static struct security_hook_list smack_hooks[] __lsm_ro_after_init = {
@@ -4565,7 +4524,6 @@ static struct security_hook_list smack_hooks[] __lsm_ro_after_init = {
 	LSM_HOOK_INIT(bprm_set_creds, smack_bprm_set_creds),
 
 	LSM_HOOK_INIT(inode_alloc_security, smack_inode_alloc_security),
-	LSM_HOOK_INIT(inode_free_security, smack_inode_free_security),
 	LSM_HOOK_INIT(inode_init_security, smack_inode_init_security),
 	LSM_HOOK_INIT(inode_link, smack_inode_link),
 	LSM_HOOK_INIT(inode_unlink, smack_inode_unlink),