linux-ext4 - Re: [PATCH 5/5] ext4: add more mount time checks of the superblock

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Date:   Mon, 18 Jun 2018 11:55:13 -0600
From:   Andreas Dilger <adilger@...ger.ca>
To:     Theodore Ts'o <tytso@....edu>
Cc:     Ext4 Developers List <linux-ext4@...r.kernel.org>,
        wen.xu@...ech.edu
Subject: Re: [PATCH 5/5] ext4: add more mount time checks of the superblock


> On Jun 17, 2018, at 9:22 PM, Theodore Ts'o <tytso@....edu> wrote:
> 
> 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@....edu>

I thought the last hunk would conflict with Jan's patch series, but that
is for e2fsck and this is for ext4...

Reviewed-by: Andreas Dilger <adilger@...ger.ca>

> ---
> fs/ext4/super.c | 37 ++++++++++++++++++++++++++-----------
> 1 file changed, 26 insertions(+), 11 deletions(-)
> 
> diff --git a/fs/ext4/super.c b/fs/ext4/super.c
> index 1f955c128e0d..b37b00befd65 100644
> --- a/fs/ext4/super.c
> +++ b/fs/ext4/super.c
> @@ -3793,6 +3793,13 @@ 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,
> @@ -3939,13 +3946,6 @@ 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 =
> @@ -3966,10 +3966,10 @@ 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,
> @@ -4023,6 +4023,13 @@ 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);
> @@ -4058,6 +4065,14 @@ 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;
> +	}

Cheers, Andreas






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