From: Tahsin Erdogan <tahsin@google.com>
Subject: ext4: Make checks for metadata_csum feature safer
References: bsc#1087007 CVE-2018-1094
Git-commit: dec214d00e0d78a08b947d7dccdfdb84407a9f4d (partial)
Patch-filtered: Only changes to metadata checksum feature checking
Patch-mainline: v4.13-rc1

This is just a small part of commit dec214d00e0d7 "ext4: xattr inode
deduplication" that makes checks for metadata_csum feature safer and is
actually needed by following fixes.

Signed-off-by: Tahsin Erdogan <tahsin@google.com>
Acked-by: Jan Kara <jack@suse.cz>

diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index 09983c774d31..fe92a63c86cb 100644
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -2720,19 +2724,20 @@ extern void ext4_group_desc_csum_set(struct super_block *sb, __u32 group,
 extern int ext4_register_li_request(struct super_block *sb,
 				    ext4_group_t first_not_zeroed);
 
-static inline int ext4_has_group_desc_csum(struct super_block *sb)
-{
-	return ext4_has_feature_gdt_csum(sb) ||
-	       EXT4_SB(sb)->s_chksum_driver != NULL;
-}
-
 static inline int ext4_has_metadata_csum(struct super_block *sb)
 {
 	WARN_ON_ONCE(ext4_has_feature_metadata_csum(sb) &&
 		     !EXT4_SB(sb)->s_chksum_driver);
 
-	return (EXT4_SB(sb)->s_chksum_driver != NULL);
+	return ext4_has_feature_metadata_csum(sb) &&
+	       (EXT4_SB(sb)->s_chksum_driver != NULL);
 }
+
+static inline int ext4_has_group_desc_csum(struct super_block *sb)
+{
+	return ext4_has_feature_gdt_csum(sb) || ext4_has_metadata_csum(sb);
+}
+
 static inline ext4_fsblk_t ext4_blocks_count(struct ext4_super_block *es)
 {
 	return ((ext4_fsblk_t)le32_to_cpu(es->s_blocks_count_hi) << 32) |