linux-kernel - Re: [PATCH v3] module: add in-kernel support for decompressing

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Date:   Fri, 10 Dec 2021 14:05:17 -0800
From:   Luis Chamberlain <mcgrof@...nel.org>
To:     Dmitry Torokhov <dmitry.torokhov@...il.com>
Cc:     Jessica Yu <jeyu@...nel.org>, Kees Cook <keescook@...omium.org>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3] module: add in-kernel support for decompressing

On Thu, Dec 09, 2021 at 10:09:17PM -0800, Dmitry Torokhov wrote:
> +static ssize_t module_xz_decompress(struct load_info *info,
> +				    const void *buf, size_t size)
> +{
> +	static const u8 signature[] = { 0xfd, '7', 'z', 'X', 'Z', 0 };
> +	struct xz_dec *xz_dec;
> +	struct xz_buf xz_buf;
> +	enum xz_ret xz_ret;
> +	size_t new_size = 0;
> +	ssize_t retval;
> +
> +	if (size < sizeof(signature) ||
> +	    memcmp(buf, signature, sizeof(signature))) {
> +		pr_err("not an xz compressed module\n");
> +		return -EINVAL;
> +	}
> +
> +	xz_dec = xz_dec_init(XZ_DYNALLOC, (u32)-1);
> +	if (!xz_dec)
> +		return -ENOMEM;
> +
> +	xz_buf.in_size = size;
> +	xz_buf.in = buf;
> +	xz_buf.in_pos = 0;
> +
> +	do {
> +		struct page *page = module_get_next_page(info);
> +		if (!page) {
> +			retval = -ENOMEM;
> +			goto out;
> +		}

This looks very similar to fw_decompress_xz_pages() on
drivers/base/firmware_loader/main.c

Is there any sharing possible with decompression between the two?

  Luis