Re: [PATCH] squashfs: fix inode lookup sanity checks

[Phillip Lougher <phillip@squashfs.org.uk>]

On 26/02/2021 09:29, Sean Nyekjaer wrote:
> When mouting a squashfs image created without inode compression it
> fails with: "unable to read inode lookup table"
> 
> It turns out that the BLOCK_OFFSET is missing when checking
> the SQUASHFS_METADATA_SIZE agaist the actual size.
> 
> Fixes: eabac19e40c0 ("squashfs: add more sanity checks in inode lookup")
> CC: stable@vger.kernel.org
> Signed-off-by: Sean Nyekjaer <sean@geanix.com>

Acked-by: phillip@squashfs.org.uk.

> ---
>   fs/squashfs/export.c      | 8 ++++++--
>   fs/squashfs/squashfs_fs.h | 1 +
>   2 files changed, 7 insertions(+), 2 deletions(-)
> 
> diff --git a/fs/squashfs/export.c b/fs/squashfs/export.c
> index eb02072d28dd..723763746238 100644
> --- a/fs/squashfs/export.c
> +++ b/fs/squashfs/export.c
> @@ -152,14 +152,18 @@ __le64 *squashfs_read_inode_lookup_table(struct super_block *sb,
>   		start = le64_to_cpu(table[n]);
>   		end = le64_to_cpu(table[n + 1]);
>   
> -		if (start >= end || (end - start) > SQUASHFS_METADATA_SIZE) {
> +		if (start >= end
> +		    || (end - start) >
> +		    (SQUASHFS_METADATA_SIZE + SQUASHFS_BLOCK_OFFSET)) {
>   			kfree(table);
>   			return ERR_PTR(-EINVAL);
>   		}
>   	}
>   
>   	start = le64_to_cpu(table[indexes - 1]);
> -	if (start >= lookup_table_start || (lookup_table_start - start) > SQUASHFS_METADATA_SIZE) {
> +	if (start >= lookup_table_start ||
> +	    (lookup_table_start - start) >
> +	    (SQUASHFS_METADATA_SIZE + SQUASHFS_BLOCK_OFFSET)) {
>   		kfree(table);
>   		return ERR_PTR(-EINVAL);
>   	}
> diff --git a/fs/squashfs/squashfs_fs.h b/fs/squashfs/squashfs_fs.h
> index 8d64edb80ebf..b3fdc8212c5f 100644
> --- a/fs/squashfs/squashfs_fs.h
> +++ b/fs/squashfs/squashfs_fs.h
> @@ -17,6 +17,7 @@
>   
>   /* size of metadata (inode and directory) blocks */
>   #define SQUASHFS_METADATA_SIZE		8192
> +#define SQUASHFS_BLOCK_OFFSET		2
>   
>   /* default size of block device I/O */
>   #ifdef CONFIG_SQUASHFS_4K_DEVBLK_SIZE
>