1 files changed, 42 insertions, 1 deletions

diff --git a/fs/ext4/balloc.c b/fs/ext4/balloc.c
index 094269488183..c1edde817be8 100644
--- a/fs/ext4/balloc.c
+++ b/fs/ext4/balloc.c
@@ -305,6 +305,38 @@ struct ext4_group_desc * ext4_get_group_desc(struct super_block *sb,
 	return desc;
 }
 
+static ext4_fsblk_t ext4_valid_block_bitmap_padding(struct super_block *sb,
+						    ext4_group_t block_group,
+						    struct buffer_head *bh)
+{
+	ext4_grpblk_t next_zero_bit;
+	unsigned long bitmap_size = sb->s_blocksize * 8;
+	unsigned int offset = num_clusters_in_group(sb, block_group);
+
+	if (bitmap_size <= offset)
+		return 0;
+
+	next_zero_bit = ext4_find_next_zero_bit(bh->b_data, bitmap_size, offset);
+
+	return (next_zero_bit < bitmap_size ? next_zero_bit : 0);
+}
+
+struct ext4_group_info *ext4_get_group_info(struct super_block *sb,
+					    ext4_group_t group)
+{
+	 struct ext4_group_info **grp_info;
+	 long indexv, indexh;
+
+	 if (unlikely(group >= EXT4_SB(sb)->s_groups_count)) {
+		 ext4_error(sb, "invalid group %u", group);
+		 return NULL;
+	 }
+	 indexv = group >> (EXT4_DESC_PER_BLOCK_BITS(sb));
+	 indexh = group & ((EXT4_DESC_PER_BLOCK(sb)) - 1);
+	 grp_info = sbi_array_rcu_deref(EXT4_SB(sb), s_group_info, indexv);
+	 return grp_info[indexh];
+}
+
 /*
  * Return the block number which was discovered to be invalid, or 0 if
  * the block bitmap is valid.
@@ -379,7 +411,7 @@ static int ext4_validate_block_bitmap(struct super_block *sb,
 
 	if (buffer_verified(bh))
 		return 0;
-	if (EXT4_MB_GRP_BBITMAP_CORRUPT(grp))
+	if (!grp || EXT4_MB_GRP_BBITMAP_CORRUPT(grp))
 		return -EFSCORRUPTED;
 
 	ext4_lock_group(sb, block_group);
@@ -402,6 +434,15 @@ static int ext4_validate_block_bitmap(struct super_block *sb,
 					EXT4_GROUP_INFO_BBITMAP_CORRUPT);
 		return -EFSCORRUPTED;
 	}
+	blk = ext4_valid_block_bitmap_padding(sb, block_group, bh);
+	if (unlikely(blk != 0)) {
+		ext4_unlock_group(sb, block_group);
+		ext4_error(sb, "bg %u: block %llu: padding at end of block bitmap is not set",
+			   block_group, blk);
+		ext4_mark_group_bitmap_corrupted(sb, block_group,
+						 EXT4_GROUP_INFO_BBITMAP_CORRUPT);
+		return -EFSCORRUPTED;
+	}
 	set_buffer_verified(bh);
 verified:
 	ext4_unlock_group(sb, block_group);