VFS: Factor out part of vfs_setxattr so it can be called from the SELinux hook for inode_setsecctx.

This factors out the part of the vfs_setxattr function that performs the
setting of the xattr and its notification. This is needed so the SELinux
implementation of inode_setsecctx can handle the setting of the xattr while
maintaining the proper separation of layers.
Signed-off-by: David P. Quigley <dpquigl@tycho.nsa.gov>
Acked-by: Serge Hallyn <serue@us.ibm.com>
Signed-off-by: James Morris <jmorris@namei.org>

fs/xattr.c

@@ -66,22 +66,28 @@ xattr_permission(struct inode *inode, const char *name, int mask)
 	return inode_permission(inode, mask);
 }
 
-int
-vfs_setxattr(struct dentry *dentry, const char *name, const void *value,
-		size_t size, int flags)
+/**
+ *  __vfs_setxattr_noperm - perform setxattr operation without performing
+ *  permission checks.
+ *
+ *  @dentry - object to perform setxattr on
+ *  @name - xattr name to set
+ *  @value - value to set @name to
+ *  @size - size of @value
+ *  @flags - flags to pass into filesystem operations
+ *
+ *  returns the result of the internal setxattr or setsecurity operations.
+ *
+ *  This function requires the caller to lock the inode's i_mutex before it
+ *  is executed. It also assumes that the caller will make the appropriate
+ *  permission checks.
+ */
+int __vfs_setxattr_noperm(struct dentry *dentry, const char *name,
+		const void *value, size_t size, int flags)
 {
 	struct inode *inode = dentry->d_inode;
-	int error;
-
-	error = xattr_permission(inode, name, MAY_WRITE);
-	if (error)
-		return error;
+	int error = -EOPNOTSUPP;
 
-	mutex_lock(&inode->i_mutex);
-	error = security_inode_setxattr(dentry, name, value, size, flags);
-	if (error)
-		goto out;
-	error = -EOPNOTSUPP;
 	if (inode->i_op->setxattr) {
 		error = inode->i_op->setxattr(dentry, name, value, size, flags);
 		if (!error) {
@@ -97,6 +103,29 @@ vfs_setxattr(struct dentry *dentry, const char *name, const void *value,
 		if (!error)
 			fsnotify_xattr(dentry);
 	}
+
+	return error;
+}
+
+
+int
+vfs_setxattr(struct dentry *dentry, const char *name, const void *value,
+		size_t size, int flags)
+{
+	struct inode *inode = dentry->d_inode;
+	int error;
+
+	error = xattr_permission(inode, name, MAY_WRITE);
+	if (error)
+		return error;
+
+	mutex_lock(&inode->i_mutex);
+	error = security_inode_setxattr(dentry, name, value, size, flags);
+	if (error)
+		goto out;
+
+	error = __vfs_setxattr_noperm(dentry, name, value, size, flags);
+
 out:
 	mutex_unlock(&inode->i_mutex);
 	return error;

include/linux/xattr.h

@@ -49,6 +49,7 @@ struct xattr_handler {
 ssize_t xattr_getsecurity(struct inode *, const char *, void *, size_t);
 ssize_t vfs_getxattr(struct dentry *, const char *, void *, size_t);
 ssize_t vfs_listxattr(struct dentry *d, char *list, size_t size);
+int __vfs_setxattr_noperm(struct dentry *, const char *, const void *, size_t, int);
 int vfs_setxattr(struct dentry *, const char *, const void *, size_t, int);
 int vfs_removexattr(struct dentry *, const char *);