linux-kernel - Re: [PATCH] btrfs compression: check string length

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Date:   Tue, 24 Sep 2019 10:01:25 +0300
From:   Nikolay Borisov <nborisov@...e.com>
To:     Pavel Machek <pavel@....cz>, clm@...com,
        David Sterba <dsterba@...e.com>, josef@...icpanda.com,
        linux-btrfs@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] btrfs compression: check string length



On 24.09.19 г. 9:14 ч., Pavel Machek wrote:
> AFAICT, with current code user could pass something like "lzox" and
> still get "lzo" compression. Check string lengths to prevent that.
> 
> Signed-off-by: Pavel Machek <pavel@...x.de>
> 
> diff --git a/fs/btrfs/compression.c b/fs/btrfs/compression.c
> index b05b361..1083ab4 100644
> --- a/fs/btrfs/compression.c
> +++ b/fs/btrfs/compression.c
> @@ -51,7 +51,7 @@ bool btrfs_compress_is_valid_type(const char *str, size_t len)
>  	for (i = 1; i < ARRAY_SIZE(btrfs_compress_types); i++) {
>  		size_t comp_len = strlen(btrfs_compress_types[i]);
>  
> -		if (len < comp_len)
> +		if (len != comp_len)
>  			continue;

It's like that so that we can support compression strings such as
zlib:9. In fact the initial version was written like you suggest:

https://www.mail-archive.com/linux-btrfs@vger.kernel.org/msg88216.html

>  
>  		if (!strncmp(btrfs_compress_types[i], str, comp_len))
>