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>

2 files changed, 5 insertions, 15 deletions

diff --git a/fs/9p/acl.c b/fs/9p/acl.c
index 6ff30b14bc76..9da967f38387 100644
--- a/fs/9p/acl.c
+++ b/fs/9p/acl.c
@@ -220,15 +220,12 @@ static int v9fs_xattr_get_acl(const struct xattr_handler *handler,
 	struct posix_acl *acl;
 	int error;
 
-	if (strcmp(name, "") != 0)
-		return -EINVAL;
-
 	v9ses = v9fs_dentry2v9ses(dentry);
 	/*
 	 * We allow set/get/list of acl when access=client is not specified
 	 */
 	if ((v9ses->flags & V9FS_ACCESS_MASK) != V9FS_ACCESS_CLIENT)
-		return v9fs_xattr_get(dentry, handler->prefix, buffer, size);
+		return v9fs_xattr_get(dentry, handler->name, buffer, size);
 
 	acl = v9fs_get_cached_acl(d_inode(dentry), handler->flags);
 	if (IS_ERR(acl))
@@ -250,16 +247,13 @@ static int v9fs_xattr_set_acl(const struct xattr_handler *handler,
 	struct v9fs_session_info *v9ses;
 	struct inode *inode = d_inode(dentry);
 
-	if (strcmp(name, "") != 0)
-		return -EINVAL;
-
 	v9ses = v9fs_dentry2v9ses(dentry);
 	/*
 	 * set the attribute on the remote. Without even looking at the
 	 * xattr value. We leave it to the server to validate
 	 */
 	if ((v9ses->flags & V9FS_ACCESS_MASK) != V9FS_ACCESS_CLIENT)
-		return v9fs_xattr_set(dentry, handler->prefix, value, size,
+		return v9fs_xattr_set(dentry, handler->name, value, size,
 				      flags);
 
 	if (S_ISLNK(inode->i_mode))
@@ -319,7 +313,7 @@ static int v9fs_xattr_set_acl(const struct xattr_handler *handler,
 	default:
 		BUG();
 	}
-	retval = v9fs_xattr_set(dentry, handler->prefix, value, size, flags);
+	retval = v9fs_xattr_set(dentry, handler->name, value, size, flags);
 	if (!retval)
 		set_cached_acl(inode, handler->flags, acl);
 err_out:
@@ -328,14 +322,14 @@ err_out:
 }
 
 const struct xattr_handler v9fs_xattr_acl_access_handler = {
-	.prefix	= XATTR_NAME_POSIX_ACL_ACCESS,
+	.name	= XATTR_NAME_POSIX_ACL_ACCESS,
 	.flags	= ACL_TYPE_ACCESS,
 	.get	= v9fs_xattr_get_acl,
 	.set	= v9fs_xattr_set_acl,
 };
 
 const struct xattr_handler v9fs_xattr_acl_default_handler = {
-	.prefix	= XATTR_NAME_POSIX_ACL_DEFAULT,
+	.name	= XATTR_NAME_POSIX_ACL_DEFAULT,
 	.flags	= ACL_TYPE_DEFAULT,
 	.get	= v9fs_xattr_get_acl,
 	.set	= v9fs_xattr_set_acl,
diff --git a/fs/9p/xattr.c b/fs/9p/xattr.c
index e3d026ac382e..9dd9b47a6c1a 100644
--- a/fs/9p/xattr.c
+++ b/fs/9p/xattr.c
@@ -143,8 +143,6 @@ static int v9fs_xattr_handler_get(const struct xattr_handler *handler,
 {
 	const char *full_name = xattr_full_name(handler, name);
 
-	if (strcmp(name, "") == 0)
-		return -EINVAL;
 	return v9fs_xattr_get(dentry, full_name, buffer, size);
 }
 
@@ -154,8 +152,6 @@ static int v9fs_xattr_handler_set(const struct xattr_handler *handler,
 {
 	const char *full_name = xattr_full_name(handler, name);
 
-	if (strcmp(name, "") == 0)
-		return -EINVAL;
 	return v9fs_xattr_set(dentry, full_name, value, size, flags);
 }