+
+/*
+ * Check permissions for extended attribute access. This is a bit complicated
+ * because different namespaces have very different rules.
+ */
+static int
+xattr_permission(struct inode *inode, const char *name, int mask)
+{
+ /*
+ * We can never set or remove an extended attribute on a read-only
+ * filesystem or on an immutable / append-only inode.
+ */
+ if (mask & MAY_WRITE) {
+ if (IS_RDONLY(inode))
+ return -EROFS;
+ if (IS_IMMUTABLE(inode) || IS_APPEND(inode))
+ return -EPERM;
+ }
+
+ /*
+ * No restriction for security.* and system.* from the VFS. Decision
+ * on these is left to the underlying filesystem / security module.
+ */
+ if (!strncmp(name, XATTR_SECURITY_PREFIX, XATTR_SECURITY_PREFIX_LEN) ||
+ !strncmp(name, XATTR_SYSTEM_PREFIX, XATTR_SYSTEM_PREFIX_LEN))
+ return 0;
+
+ /*
+ * The trusted.* namespace can only accessed by a privilegued user.
+ */
+ if (!strncmp(name, XATTR_TRUSTED_PREFIX, XATTR_TRUSTED_PREFIX_LEN))
+ return (capable(CAP_SYS_ADMIN) ? 0 : -EPERM);
+
+ if (!strncmp(name, XATTR_USER_PREFIX, XATTR_USER_PREFIX_LEN)) {
+ if (!S_ISREG(inode->i_mode) &&
+ (!S_ISDIR(inode->i_mode) || inode->i_mode & S_ISVTX))
+ return -EPERM;
+ }
+
+ return permission(inode, mask, NULL);
+}
+
+int
+vfs_setxattr(struct dentry *dentry, char *name, 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 = -EOPNOTSUPP;
+ if (inode->i_op->setxattr) {
+ error = inode->i_op->setxattr(dentry, name, value, size, flags);
+ if (!error) {
+ fsnotify_xattr(dentry);
+ security_inode_post_setxattr(dentry, name, value,
+ size, flags);
+ }
+ } else if (!strncmp(name, XATTR_SECURITY_PREFIX,
+ XATTR_SECURITY_PREFIX_LEN)) {
+ const char *suffix = name + XATTR_SECURITY_PREFIX_LEN;
+ error = security_inode_setsecurity(inode, suffix, value,
+ size, flags);
+ if (!error)
+ fsnotify_xattr(dentry);
+ }
+out:
+ mutex_unlock(&inode->i_mutex);
+ return error;
+}
+EXPORT_SYMBOL_GPL(vfs_setxattr);
+
+ssize_t
+vfs_getxattr(struct dentry *dentry, char *name, void *value, size_t size)
+{
+ struct inode *inode = dentry->d_inode;
+ int error;
+
+ error = xattr_permission(inode, name, MAY_READ);
+ if (error)
+ return error;
+
+ error = security_inode_getxattr(dentry, name);
+ if (error)
+ return error;
+
+ if (inode->i_op->getxattr)
+ error = inode->i_op->getxattr(dentry, name, value, size);
+ else
+ error = -EOPNOTSUPP;
+
+ if (!strncmp(name, XATTR_SECURITY_PREFIX,
+ XATTR_SECURITY_PREFIX_LEN)) {
+ const char *suffix = name + XATTR_SECURITY_PREFIX_LEN;
+ int ret = security_inode_getsecurity(inode, suffix, value,
+ size, error);
+ /*
+ * Only overwrite the return value if a security module
+ * is actually active.
+ */
+ if (ret != -EOPNOTSUPP)
+ error = ret;
+ }
+
+ return error;
+}
+EXPORT_SYMBOL_GPL(vfs_getxattr);
+
+int
+vfs_removexattr(struct dentry *dentry, char *name)
+{
+ struct inode *inode = dentry->d_inode;
+ int error;
+
+ if (!inode->i_op->removexattr)
+ return -EOPNOTSUPP;
+
+ error = xattr_permission(inode, name, MAY_WRITE);
+ if (error)
+ return error;
+
+ error = security_inode_removexattr(dentry, name);
+ if (error)
+ return error;
+
+ mutex_lock(&inode->i_mutex);
+ error = inode->i_op->removexattr(dentry, name);
+ mutex_unlock(&inode->i_mutex);
+
+ if (!error)
+ fsnotify_xattr(dentry);
+ return error;
+}
+EXPORT_SYMBOL_GPL(vfs_removexattr);
+
+