Security: Add hook to calculate context based on a negative dentry.

There is a time where we need to calculate a context without the
inode having been created yet. To do this we take the negative dentry and
calculate a context based on the process and the parent directory contexts.

Acked-by: Eric Paris <eparis@redhat.com>
Acked-by: James Morris <james.l.morris@oracle.com>
Signed-off-by: Matthew N. Dodd <Matthew.Dodd@sparta.com>
Signed-off-by: Miguel Rodel Felipe <Rodel_FM@dsi.a-star.edu.sg>
Signed-off-by: Phua Eu Gene <PHUA_Eu_Gene@dsi.a-star.edu.sg>
Signed-off-by: Khin Mi Mi Aung <Mi_Mi_AUNG@dsi.a-star.edu.sg>
Signed-off-by: Steve Dickson <steved@redhat.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
diff --git a/include/linux/security.h b/include/linux/security.h
index 4686491..c2af462 100644
--- a/include/linux/security.h
+++ b/include/linux/security.h
@@ -26,6 +26,7 @@
 #include <linux/capability.h>
 #include <linux/slab.h>
 #include <linux/err.h>
+#include <linux/string.h>
 
 struct linux_binprm;
 struct cred;
@@ -306,6 +307,15 @@
  *	Parse a string of security data filling in the opts structure
  *	@options string containing all mount options known by the LSM
  *	@opts binary data structure usable by the LSM
+ * @dentry_init_security:
+ *	Compute a context for a dentry as the inode is not yet available
+ *	since NFSv4 has no label backed by an EA anyway.
+ *	@dentry dentry to use in calculating the context.
+ *	@mode mode used to determine resource type.
+ *	@name name of the last path component used to create file
+ *	@ctx pointer to place the pointer to the resulting context in.
+ *	@ctxlen point to place the length of the resulting context.
+ *
  *
  * Security hooks for inode operations.
  *
@@ -1443,6 +1453,10 @@
 	int (*sb_clone_mnt_opts) (const struct super_block *oldsb,
 				   struct super_block *newsb);
 	int (*sb_parse_opts_str) (char *options, struct security_mnt_opts *opts);
+	int (*dentry_init_security) (struct dentry *dentry, int mode,
+					struct qstr *name, void **ctx,
+					u32 *ctxlen);
+
 
 #ifdef CONFIG_SECURITY_PATH
 	int (*path_unlink) (struct path *dir, struct dentry *dentry);
@@ -1729,6 +1743,9 @@
 int security_sb_clone_mnt_opts(const struct super_block *oldsb,
 				struct super_block *newsb);
 int security_sb_parse_opts_str(char *options, struct security_mnt_opts *opts);
+int security_dentry_init_security(struct dentry *dentry, int mode,
+					struct qstr *name, void **ctx,
+					u32 *ctxlen);
 
 int security_inode_alloc(struct inode *inode);
 void security_inode_free(struct inode *inode);
@@ -2035,6 +2052,16 @@
 static inline void security_inode_free(struct inode *inode)
 { }
 
+static inline int security_dentry_init_security(struct dentry *dentry,
+						 int mode,
+						 struct qstr *name,
+						 void **ctx,
+						 u32 *ctxlen)
+{
+	return -EOPNOTSUPP;
+}
+
+
 static inline int security_inode_init_security(struct inode *inode,
 						struct inode *dir,
 						const struct qstr *qstr,