ext4: add more mount time checks of the superblock

commit bfe0a5f4 upstream.

The kernel's ext4 mount-time checks were more permissive than
e2fsprogs's libext2fs checks when opening a file system.  The
superblock is considered too insane for debugfs or e2fsck to operate
on it, the kernel has no business trying to mount it.

This will make file system fuzzing tools work harder, but the failure
cases that they find will be more useful and be easier to evaluate.
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Cc: stable@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

fs/ext4/super.c

@@ -3485,6 +3485,13 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent)
 			 le32_to_cpu(es->s_log_block_size));
 		goto failed_mount;
 	}
+	if (le32_to_cpu(es->s_log_cluster_size) >
+	    (EXT4_MAX_CLUSTER_LOG_SIZE - EXT4_MIN_BLOCK_LOG_SIZE)) {
+		ext4_msg(sb, KERN_ERR,
+			 "Invalid log cluster size: %u",
+			 le32_to_cpu(es->s_log_cluster_size));
+		goto failed_mount;
+	}
 
 	if (le16_to_cpu(sbi->s_es->s_reserved_gdt_blocks) > (blocksize / 4)) {
 		ext4_msg(sb, KERN_ERR,
@@ -3630,13 +3637,6 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent)
 				 "block size (%d)", clustersize, blocksize);
 			goto failed_mount;
 		}
-		if (le32_to_cpu(es->s_log_cluster_size) >
-		    (EXT4_MAX_CLUSTER_LOG_SIZE - EXT4_MIN_BLOCK_LOG_SIZE)) {
-			ext4_msg(sb, KERN_ERR,
-				 "Invalid log cluster size: %u",
-				 le32_to_cpu(es->s_log_cluster_size));
-			goto failed_mount;
-		}
 		sbi->s_cluster_bits = le32_to_cpu(es->s_log_cluster_size) -
 			le32_to_cpu(es->s_log_block_size);
 		sbi->s_clusters_per_group =
@@ -3657,10 +3657,10 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent)
 		}
 	} else {
 		if (clustersize != blocksize) {
-			ext4_warning(sb, "fragment/cluster size (%d) != "
-				     "block size (%d)", clustersize,
-				     blocksize);
-			clustersize = blocksize;
+			ext4_msg(sb, KERN_ERR,
+				 "fragment/cluster size (%d) != "
+				 "block size (%d)", clustersize, blocksize);
+			goto failed_mount;
 		}
 		if (sbi->s_blocks_per_group > blocksize * 8) {
 			ext4_msg(sb, KERN_ERR,
@@ -3714,6 +3714,13 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent)
 			 ext4_blocks_count(es));
 		goto failed_mount;
 	}
+	if ((es->s_first_data_block == 0) && (es->s_log_block_size == 0) &&
+	    (sbi->s_cluster_ratio == 1)) {
+		ext4_msg(sb, KERN_WARNING, "bad geometry: first data "
+			 "block is 0 with a 1k block and cluster size");
+		goto failed_mount;
+	}
+
 	blocks_count = (ext4_blocks_count(es) -
 			le32_to_cpu(es->s_first_data_block) +
 			EXT4_BLOCKS_PER_GROUP(sb) - 1);
@@ -3749,6 +3756,14 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent)
 		ret = -ENOMEM;
 		goto failed_mount;
 	}
+	if (((u64)sbi->s_groups_count * sbi->s_inodes_per_group) !=
+	    le32_to_cpu(es->s_inodes_count)) {
+		ext4_msg(sb, KERN_ERR, "inodes count not valid: %u vs %llu",
+			 le32_to_cpu(es->s_inodes_count),
+			 ((u64)sbi->s_groups_count * sbi->s_inodes_per_group));
+		ret = -EINVAL;
+		goto failed_mount;
+	}
 
 	bgl_lock_init(sbi->s_blockgroup_lock);