vfs: Distinguish between full xattr names and proper prefixes

Add an additional "name" field to struct xattr_handler.  When the name
is set, the handler matches attributes with exactly that name.  When the
prefix is set instead, the handler matches attributes with the given
prefix and with a non-empty suffix.

This patch should avoid bugs like the one fixed in commit c361016a in
the future.

Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
Reviewed-by: James Morris <james.l.morris@oracle.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

1 files changed, 11 insertions, 0 deletions

diff --git a/include/linux/xattr.h b/include/linux/xattr.h
index 45fa3456a0cc..03c847fb6cc1 100644
--- a/include/linux/xattr.h
+++ b/include/linux/xattr.h
@@ -19,7 +19,13 @@
 struct inode;
 struct dentry;
 
+/*
+ * struct xattr_handler: When @name is set, match attributes with exactly that
+ * name.  When @prefix is set instead, match attributes with that prefix and
+ * with a non-empty suffix.
+ */
 struct xattr_handler {
+	const char *name;
 	const char *prefix;
 	int flags;      /* fs private flags */
 	size_t (*list)(const struct xattr_handler *, struct dentry *dentry,
@@ -54,6 +60,11 @@ int generic_removexattr(struct dentry *dentry, const char *name);
 ssize_t vfs_getxattr_alloc(struct dentry *dentry, const char *name,
 			   char **xattr_value, size_t size, gfp_t flags);
 
+static inline const char *xattr_prefix(const struct xattr_handler *handler)
+{
+	return handler->prefix ?: handler->name;
+}
+
 struct simple_xattrs {
 	struct list_head head;
 	spinlock_t lock;