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>

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,

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);
 }
 

fs/ext2/xattr_security.c

@@ -28,8 +28,6 @@ ext2_xattr_security_get(const struct xattr_handler *handler,
 			struct dentry *dentry, const char *name,
 			void *buffer, size_t size)
 {
-	if (strcmp(name, "") == 0)
-		return -EINVAL;
 	return ext2_xattr_get(d_inode(dentry), EXT2_XATTR_INDEX_SECURITY, name,
 			      buffer, size);
 }
@@ -39,8 +37,6 @@ ext2_xattr_security_set(const struct xattr_handler *handler,
 			struct dentry *dentry, const char *name,
 			const void *value, size_t size, int flags)
 {
-	if (strcmp(name, "") == 0)
-		return -EINVAL;
 	return ext2_xattr_set(d_inode(dentry), EXT2_XATTR_INDEX_SECURITY, name,
 			      value, size, flags);
 }

fs/ext2/xattr_trusted.c

@@ -32,8 +32,6 @@ ext2_xattr_trusted_get(const struct xattr_handler *handler,
 		       struct dentry *dentry, const char *name,
 		       void *buffer, size_t size)
 {
-	if (strcmp(name, "") == 0)
-		return -EINVAL;
 	return ext2_xattr_get(d_inode(dentry), EXT2_XATTR_INDEX_TRUSTED, name,
 			      buffer, size);
 }
@@ -43,8 +41,6 @@ ext2_xattr_trusted_set(const struct xattr_handler *handler,
 		       struct dentry *dentry, const char *name,
 		       const void *value, size_t size, int flags)
 {
-	if (strcmp(name, "") == 0)
-		return -EINVAL;
 	return ext2_xattr_set(d_inode(dentry), EXT2_XATTR_INDEX_TRUSTED, name,
 			      value, size, flags);
 }

fs/ext2/xattr_user.c

@@ -34,8 +34,6 @@ ext2_xattr_user_get(const struct xattr_handler *handler,
 		    struct dentry *dentry, const char *name,
 		    void *buffer, size_t size)
 {
-	if (strcmp(name, "") == 0)
-		return -EINVAL;
 	if (!test_opt(dentry->d_sb, XATTR_USER))
 		return -EOPNOTSUPP;
 	return ext2_xattr_get(d_inode(dentry), EXT2_XATTR_INDEX_USER,
@@ -47,8 +45,6 @@ ext2_xattr_user_set(const struct xattr_handler *handler,
 		    struct dentry *dentry, const char *name,
 		    const void *value, size_t size, int flags)
 {
-	if (strcmp(name, "") == 0)
-		return -EINVAL;
 	if (!test_opt(dentry->d_sb, XATTR_USER))
 		return -EOPNOTSUPP;
 

fs/ext4/xattr_security.c

@@ -33,8 +33,6 @@ ext4_xattr_security_get(const struct xattr_handler *handler,
 			struct dentry *dentry, const char *name,
 			void *buffer, size_t size)
 {
-	if (strcmp(name, "") == 0)
-		return -EINVAL;
 	return ext4_xattr_get(d_inode(dentry), EXT4_XATTR_INDEX_SECURITY,
 			      name, buffer, size);
 }
@@ -44,8 +42,6 @@ ext4_xattr_security_set(const struct xattr_handler *handler,
 			struct dentry *dentry, const char *name,
 			const void *value, size_t size, int flags)
 {
-	if (strcmp(name, "") == 0)
-		return -EINVAL;
 	return ext4_xattr_set(d_inode(dentry), EXT4_XATTR_INDEX_SECURITY,
 			      name, value, size, flags);
 }

fs/ext4/xattr_trusted.c

@@ -36,8 +36,6 @@ ext4_xattr_trusted_get(const struct xattr_handler *handler,
 		       struct dentry *dentry, const char *name, void *buffer,
 		       size_t size)
 {
-	if (strcmp(name, "") == 0)
-		return -EINVAL;
 	return ext4_xattr_get(d_inode(dentry), EXT4_XATTR_INDEX_TRUSTED,
 			      name, buffer, size);
 }
@@ -47,8 +45,6 @@ ext4_xattr_trusted_set(const struct xattr_handler *handler,
 		       struct dentry *dentry, const char *name,
 		       const void *value, size_t size, int flags)
 {
-	if (strcmp(name, "") == 0)
-		return -EINVAL;
 	return ext4_xattr_set(d_inode(dentry), EXT4_XATTR_INDEX_TRUSTED,
 			      name, value, size, flags);
 }

fs/ext4/xattr_user.c

@@ -35,8 +35,6 @@ ext4_xattr_user_get(const struct xattr_handler *handler,
 		    struct dentry *dentry, const char *name,
 		    void *buffer, size_t size)
 {
-	if (strcmp(name, "") == 0)
-		return -EINVAL;
 	if (!test_opt(dentry->d_sb, XATTR_USER))
 		return -EOPNOTSUPP;
 	return ext4_xattr_get(d_inode(dentry), EXT4_XATTR_INDEX_USER,
@@ -48,8 +46,6 @@ ext4_xattr_user_set(const struct xattr_handler *handler,
 		    struct dentry *dentry, const char *name,
 		    const void *value, size_t size, int flags)
 {
-	if (strcmp(name, "") == 0)
-		return -EINVAL;
 	if (!test_opt(dentry->d_sb, XATTR_USER))
 		return -EOPNOTSUPP;
 	return ext4_xattr_set(d_inode(dentry), EXT4_XATTR_INDEX_USER,

fs/f2fs/xattr.c

@@ -30,6 +30,7 @@ static size_t f2fs_xattr_generic_list(const struct xattr_handler *handler,
 		const char *name, size_t len)
 {
 	struct f2fs_sb_info *sbi = F2FS_SB(dentry->d_sb);
+	const char *prefix;
 	int total_len, prefix_len;
 
 	switch (handler->flags) {
@@ -47,10 +48,11 @@ static size_t f2fs_xattr_generic_list(const struct xattr_handler *handler,
 		return -EINVAL;
 	}
 
-	prefix_len = strlen(handler->prefix);
+	prefix = xattr_prefix(handler);
+	prefix_len = strlen(prefix);
 	total_len = prefix_len + len + 1;
 	if (list && total_len <= list_size) {
-		memcpy(list, handler->prefix, prefix_len);
+		memcpy(list, prefix, prefix_len);
 		memcpy(list + prefix_len, name, len);
 		list[prefix_len + len] = '\0';
 	}
@@ -77,8 +79,6 @@ static int f2fs_xattr_generic_get(const struct xattr_handler *handler,
 	default:
 		return -EINVAL;
 	}
-	if (strcmp(name, "") == 0)
-		return -EINVAL;
 	return f2fs_getxattr(d_inode(dentry), handler->flags, name,
 			     buffer, size, NULL);
 }
@@ -103,9 +103,6 @@ static int f2fs_xattr_generic_set(const struct xattr_handler *handler,
 	default:
 		return -EINVAL;
 	}
-	if (strcmp(name, "") == 0)
-		return -EINVAL;
-
 	return f2fs_setxattr(d_inode(dentry), handler->flags, name,
 					value, size, NULL, flags);
 }
@@ -114,7 +111,7 @@ static size_t f2fs_xattr_advise_list(const struct xattr_handler *handler,
 		struct dentry *dentry, char *list, size_t list_size,
 		const char *name, size_t len)
 {
-	const char *xname = F2FS_SYSTEM_ADVISE_PREFIX;
+	const char *xname = F2FS_SYSTEM_ADVISE_NAME;
 	size_t size;
 
 	size = strlen(xname) + 1;
@@ -129,9 +126,6 @@ static int f2fs_xattr_advise_get(const struct xattr_handler *handler,
 {
 	struct inode *inode = d_inode(dentry);
 
-	if (strcmp(name, "") != 0)
-		return -EINVAL;
-
 	if (buffer)
 		*((char *)buffer) = F2FS_I(inode)->i_advise;
 	return sizeof(char);
@@ -143,8 +137,6 @@ static int f2fs_xattr_advise_set(const struct xattr_handler *handler,
 {
 	struct inode *inode = d_inode(dentry);
 
-	if (strcmp(name, "") != 0)
-		return -EINVAL;
 	if (!inode_owner_or_capable(inode))
 		return -EPERM;
 	if (value == NULL)
@@ -197,7 +189,7 @@ const struct xattr_handler f2fs_xattr_trusted_handler = {
 };
 
 const struct xattr_handler f2fs_xattr_advise_handler = {
-	.prefix = F2FS_SYSTEM_ADVISE_PREFIX,
+	.name	= F2FS_SYSTEM_ADVISE_NAME,
 	.flags	= F2FS_XATTR_INDEX_ADVISE,
 	.list   = f2fs_xattr_advise_list,
 	.get    = f2fs_xattr_advise_get,

fs/f2fs/xattr.h

@@ -27,7 +27,7 @@
 #define F2FS_XATTR_REFCOUNT_MAX         1024
 
 /* Name indexes */
-#define F2FS_SYSTEM_ADVISE_PREFIX		"system.advise"
+#define F2FS_SYSTEM_ADVISE_NAME			"system.advise"
 #define F2FS_XATTR_INDEX_USER			1
 #define F2FS_XATTR_INDEX_POSIX_ACL_ACCESS	2
 #define F2FS_XATTR_INDEX_POSIX_ACL_DEFAULT	3

fs/hfsplus/xattr.c

@@ -431,9 +431,6 @@ int hfsplus_setxattr(struct dentry *dentry, const char *name,
 	char *xattr_name;
 	int res;
 
-	if (!strcmp(name, ""))
-		return -EINVAL;
-
 	xattr_name = kmalloc(NLS_MAX_CHARSET_SIZE * HFSPLUS_ATTR_MAX_STRLEN + 1,
 		GFP_KERNEL);
 	if (!xattr_name)
@@ -589,9 +586,6 @@ ssize_t hfsplus_getxattr(struct dentry *dentry, const char *name,
 	int res;
 	char *xattr_name;
 
-	if (!strcmp(name, ""))
-		return -EINVAL;
-
 	xattr_name = kmalloc(NLS_MAX_CHARSET_SIZE * HFSPLUS_ATTR_MAX_STRLEN + 1,
 			     GFP_KERNEL);
 	if (!xattr_name)
@@ -853,9 +847,6 @@ static int hfsplus_osx_getxattr(const struct xattr_handler *handler,
 				struct dentry *dentry, const char *name,
 				void *buffer, size_t size)
 {
-	if (!strcmp(name, ""))
-		return -EINVAL;
-
 	/*
 	 * Don't allow retrieving properly prefixed attributes
 	 * by prepending them with "osx."
@@ -876,9 +867,6 @@ static int hfsplus_osx_setxattr(const struct xattr_handler *handler,
 				struct dentry *dentry, const char *name,
 				const void *buffer, size_t size, int flags)
 {
-	if (!strcmp(name, ""))
-		return -EINVAL;
-
 	/*
 	 * Don't allow setting properly prefixed attributes
 	 * by prepending them with "osx."

fs/jffs2/security.c

@@ -52,9 +52,6 @@ static int jffs2_security_getxattr(const struct xattr_handler *handler,
 				   struct dentry *dentry, const char *name,
 				   void *buffer, size_t size)
 {
-	if (!strcmp(name, ""))
-		return -EINVAL;
-
 	return do_jffs2_getxattr(d_inode(dentry), JFFS2_XPREFIX_SECURITY,
 				 name, buffer, size);
 }
@@ -63,9 +60,6 @@ static int jffs2_security_setxattr(const struct xattr_handler *handler,
 				   struct dentry *dentry, const char *name,
 				   const void *buffer, size_t size, int flags)
 {
-	if (!strcmp(name, ""))
-		return -EINVAL;
-
 	return do_jffs2_setxattr(d_inode(dentry), JFFS2_XPREFIX_SECURITY,
 				 name, buffer, size, flags);
 }

fs/jffs2/xattr_trusted.c

@@ -20,8 +20,6 @@ static int jffs2_trusted_getxattr(const struct xattr_handler *handler,
 				  struct dentry *dentry, const char *name,
 				  void *buffer, size_t size)
 {
-	if (!strcmp(name, ""))
-		return -EINVAL;
 	return do_jffs2_getxattr(d_inode(dentry), JFFS2_XPREFIX_TRUSTED,
 				 name, buffer, size);
 }
@@ -30,8 +28,6 @@ static int jffs2_trusted_setxattr(const struct xattr_handler *handler,
 				  struct dentry *dentry, const char *name,
 				  const void *buffer, size_t size, int flags)
 {
-	if (!strcmp(name, ""))
-		return -EINVAL;
 	return do_jffs2_setxattr(d_inode(dentry), JFFS2_XPREFIX_TRUSTED,
 				 name, buffer, size, flags);
 }

fs/jffs2/xattr_user.c

@@ -20,8 +20,6 @@ static int jffs2_user_getxattr(const struct xattr_handler *handler,
 			       struct dentry *dentry, const char *name,
 			       void *buffer, size_t size)
 {
-	if (!strcmp(name, ""))
-		return -EINVAL;
 	return do_jffs2_getxattr(d_inode(dentry), JFFS2_XPREFIX_USER,
 				 name, buffer, size);
 }
@@ -30,8 +28,6 @@ static int jffs2_user_setxattr(const struct xattr_handler *handler,
 			       struct dentry *dentry, const char *name,
 			       const void *buffer, size_t size, int flags)
 {
-	if (!strcmp(name, ""))
-		return -EINVAL;
 	return do_jffs2_setxattr(d_inode(dentry), JFFS2_XPREFIX_USER,
 				 name, buffer, size, flags);
 }

fs/nfs/nfs4proc.c

@@ -6253,9 +6253,6 @@ static int nfs4_xattr_set_nfs4_acl(const struct xattr_handler *handler,
 				   const void *buf, size_t buflen,
 				   int flags)
 {
-	if (strcmp(key, "") != 0)
-		return -EINVAL;
-
 	return nfs4_proc_set_acl(d_inode(dentry), buf, buflen);
 }
 
@@ -6263,9 +6260,6 @@ static int nfs4_xattr_get_nfs4_acl(const struct xattr_handler *handler,
 				   struct dentry *dentry, const char *key,
 				   void *buf, size_t buflen)
 {
-	if (strcmp(key, "") != 0)
-		return -EINVAL;
-
 	return nfs4_proc_get_acl(d_inode(dentry), buf, buflen);
 }
 
@@ -8834,7 +8828,7 @@ const struct nfs_rpc_ops nfs_v4_clientops = {
 };
 
 static const struct xattr_handler nfs4_xattr_nfs4_acl_handler = {
-	.prefix	= XATTR_NAME_NFSV4_ACL,
+	.name	= XATTR_NAME_NFSV4_ACL,
 	.list	= nfs4_xattr_list_nfs4_acl,
 	.get	= nfs4_xattr_get_nfs4_acl,
 	.set	= nfs4_xattr_set_nfs4_acl,

fs/ocfs2/xattr.c

@@ -544,8 +544,7 @@ static inline const char *ocfs2_xattr_prefix(int name_index)
 
 	if (name_index > 0 && name_index < OCFS2_XATTR_MAX)
 		handler = ocfs2_xattr_handler_map[name_index];
-
-	return handler ? handler->prefix : NULL;
+	return handler ? xattr_prefix(handler) : NULL;
 }
 
 static u32 ocfs2_xattr_name_hash(struct inode *inode,
@@ -7249,8 +7248,6 @@ static int ocfs2_xattr_security_get(const struct xattr_handler *handler,
 				    struct dentry *dentry, const char *name,
 				    void *buffer, size_t size)
 {
-	if (strcmp(name, "") == 0)
-		return -EINVAL;
 	return ocfs2_xattr_get(d_inode(dentry), OCFS2_XATTR_INDEX_SECURITY,
 			       name, buffer, size);
 }
@@ -7259,9 +7256,6 @@ static int ocfs2_xattr_security_set(const struct xattr_handler *handler,
 				    struct dentry *dentry, const char *name,
 				    const void *value, size_t size, int flags)
 {
-	if (strcmp(name, "") == 0)
-		return -EINVAL;
-
 	return ocfs2_xattr_set(d_inode(dentry), OCFS2_XATTR_INDEX_SECURITY,
 			       name, value, size, flags);
 }
@@ -7345,8 +7339,6 @@ static int ocfs2_xattr_trusted_get(const struct xattr_handler *handler,
 				   struct dentry *dentry, const char *name,
 				   void *buffer, size_t size)
 {
-	if (strcmp(name, "") == 0)
-		return -EINVAL;
 	return ocfs2_xattr_get(d_inode(dentry), OCFS2_XATTR_INDEX_TRUSTED,
 			       name, buffer, size);
 }
@@ -7355,9 +7347,6 @@ static int ocfs2_xattr_trusted_set(const struct xattr_handler *handler,
 				   struct dentry *dentry, const char *name,
 				   const void *value, size_t size, int flags)
 {
-	if (strcmp(name, "") == 0)
-		return -EINVAL;
-
 	return ocfs2_xattr_set(d_inode(dentry), OCFS2_XATTR_INDEX_TRUSTED,
 			       name, value, size, flags);
 }
@@ -7398,8 +7387,6 @@ static int ocfs2_xattr_user_get(const struct xattr_handler *handler,
 {
 	struct ocfs2_super *osb = OCFS2_SB(dentry->d_sb);
 
-	if (strcmp(name, "") == 0)
-		return -EINVAL;
 	if (osb->s_mount_opt & OCFS2_MOUNT_NOUSERXATTR)
 		return -EOPNOTSUPP;
 	return ocfs2_xattr_get(d_inode(dentry), OCFS2_XATTR_INDEX_USER, name,
@@ -7412,8 +7399,6 @@ static int ocfs2_xattr_user_set(const struct xattr_handler *handler,
 {
 	struct ocfs2_super *osb = OCFS2_SB(dentry->d_sb);
 
-	if (strcmp(name, "") == 0)
-		return -EINVAL;
 	if (osb->s_mount_opt & OCFS2_MOUNT_NOUSERXATTR)
 		return -EOPNOTSUPP;
 

fs/posix_acl.c

@@ -769,8 +769,6 @@ posix_acl_xattr_get(const struct xattr_handler *handler,
 	struct posix_acl *acl;
 	int error;
 
-	if (strcmp(name, "") != 0)
-		return -EINVAL;
 	if (!IS_POSIXACL(d_backing_inode(dentry)))
 		return -EOPNOTSUPP;
 	if (d_is_symlink(dentry))
@@ -797,8 +795,6 @@ posix_acl_xattr_set(const struct xattr_handler *handler,
 	struct posix_acl *acl = NULL;
 	int ret;
 
-	if (strcmp(name, "") != 0)
-		return -EINVAL;
 	if (!IS_POSIXACL(inode))
 		return -EOPNOTSUPP;
 	if (!inode->i_op->set_acl)
@@ -832,7 +828,7 @@ posix_acl_xattr_list(const struct xattr_handler *handler,
 		     struct dentry *dentry, char *list, size_t list_size,
 		     const char *name, size_t name_len)
 {
-	const char *xname = handler->prefix;
+	const char *xname = handler->name;
 	size_t size;
 
 	if (!IS_POSIXACL(d_backing_inode(dentry)))
@@ -845,7 +841,7 @@ posix_acl_xattr_list(const struct xattr_handler *handler,
 }
 
 const struct xattr_handler posix_acl_access_xattr_handler = {
-	.prefix = XATTR_NAME_POSIX_ACL_ACCESS,
+	.name = XATTR_NAME_POSIX_ACL_ACCESS,
 	.flags = ACL_TYPE_ACCESS,
 	.list = posix_acl_xattr_list,
 	.get = posix_acl_xattr_get,
@@ -854,7 +850,7 @@ const struct xattr_handler posix_acl_access_xattr_handler = {
 EXPORT_SYMBOL_GPL(posix_acl_access_xattr_handler);
 
 const struct xattr_handler posix_acl_default_xattr_handler = {
-	.prefix = XATTR_NAME_POSIX_ACL_DEFAULT,
+	.name = XATTR_NAME_POSIX_ACL_DEFAULT,
 	.flags = ACL_TYPE_DEFAULT,
 	.list = posix_acl_xattr_list,
 	.get = posix_acl_xattr_get,

fs/reiserfs/xattr.c

@@ -756,7 +756,8 @@ find_xattr_handler_prefix(const struct xattr_handler **handlers,
 		return NULL;
 
 	for_each_xattr_handler(handlers, xah) {
-		if (strncmp(xah->prefix, name, strlen(xah->prefix)) == 0)
+		const char *prefix = xattr_prefix(xah);
+		if (strncmp(prefix, name, strlen(prefix)) == 0)
 			break;
 	}
 

fs/squashfs/xattr.c

@@ -228,9 +228,6 @@ static int squashfs_xattr_handler_get(const struct xattr_handler *handler,
 				      struct dentry *d, const char *name,
 				      void *buffer, size_t size)
 {
-	if (name[0] == '\0')
-		return  -EINVAL;
-
 	return squashfs_xattr_get(d_inode(d), handler->flags, name,
 		buffer, size);
 }

fs/xattr.c

@@ -681,13 +681,20 @@ xattr_resolve_name(const struct xattr_handler **handlers, const char **name)
 		return NULL;
 
 	for_each_xattr_handler(handlers, handler) {
-		const char *n = strcmp_prefix(*name, handler->prefix);
+		const char *n;
+
+		n = strcmp_prefix(*name, xattr_prefix(handler));
 		if (n) {
+			if (!handler->prefix ^ !*n) {
+				if (*n)
+					continue;
+				return ERR_PTR(-EINVAL);
+			}
 			*name = n;
-			break;
+			return handler;
 		}
 	}
-	return handler;
+	return ERR_PTR(-EOPNOTSUPP);
 }
 
 /*
@@ -699,8 +706,8 @@ generic_getxattr(struct dentry *dentry, const char *name, void *buffer, size_t s
 	const struct xattr_handler *handler;
 
 	handler = xattr_resolve_name(dentry->d_sb->s_xattr, &name);
-	if (!handler)
-		return -EOPNOTSUPP;
+	if (IS_ERR(handler))
+		return PTR_ERR(handler);
 	return handler->get(handler, dentry, name, buffer, size);
 }
 
@@ -746,8 +753,8 @@ generic_setxattr(struct dentry *dentry, const char *name, const void *value, siz
 	if (size == 0)
 		value = "";  /* empty EA, do not remove */
 	handler = xattr_resolve_name(dentry->d_sb->s_xattr, &name);
-	if (!handler)
-		return -EOPNOTSUPP;
+	if (IS_ERR(handler))
+		return PTR_ERR(handler);
 	return handler->set(handler, dentry, name, value, size, flags);
 }
 
@@ -761,8 +768,8 @@ generic_removexattr(struct dentry *dentry, const char *name)
 	const struct xattr_handler *handler;
 
 	handler = xattr_resolve_name(dentry->d_sb->s_xattr, &name);
-	if (!handler)
-		return -EOPNOTSUPP;
+	if (IS_ERR(handler))
+		return PTR_ERR(handler);
 	return handler->set(handler, dentry, name, NULL, 0, XATTR_REPLACE);
 }
 
@@ -789,7 +796,7 @@ EXPORT_SYMBOL(generic_removexattr);
 const char *xattr_full_name(const struct xattr_handler *handler,
 			    const char *name)
 {
-	size_t prefix_len = strlen(handler->prefix);
+	size_t prefix_len = strlen(xattr_prefix(handler));
 
 	return name - prefix_len;
 }

fs/xfs/xfs_xattr.c

@@ -39,9 +39,6 @@ xfs_xattr_get(const struct xattr_handler *handler, struct dentry *dentry,
 	struct xfs_inode *ip = XFS_I(d_inode(dentry));
 	int error, asize = size;
 
-	if (strcmp(name, "") == 0)
-		return -EINVAL;
-
 	/* Convert Linux syscall to XFS internal ATTR flags */
 	if (!size) {
 		xflags |= ATTR_KERNOVAL;
@@ -84,9 +81,6 @@ xfs_xattr_set(const struct xattr_handler *handler, struct dentry *dentry,
 	struct xfs_inode	*ip = XFS_I(d_inode(dentry));
 	int			error;
 
-	if (strcmp(name, "") == 0)
-		return -EINVAL;
-
 	/* Convert Linux syscall to XFS internal ATTR flags */
 	if (flags & XATTR_CREATE)
 		xflags |= ATTR_CREATE;

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;