linux-kernel - Re: [PATCH v3 18/19] firmware: Add request_partial_firmware_into

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Date:   Wed, 29 Jul 2020 08:22:17 +0200
From:   Takashi Iwai <tiwai@...e.de>
To:     Luis Chamberlain <mcgrof@...nel.org>
Cc:     Kees Cook <keescook@...omium.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Scott Branden <scott.branden@...adcom.com>,
        Mimi Zohar <zohar@...ux.ibm.com>, Jessica Yu <jeyu@...nel.org>,
        SeongJae Park <sjpark@...zon.de>,
        KP Singh <kpsingh@...omium.org>, linux-efi@...r.kernel.org,
        linux-security-module@...r.kernel.org,
        linux-integrity@...r.kernel.org, selinux@...r.kernel.org,
        linux-kselftest@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 18/19] firmware: Add request_partial_firmware_into_buf()

On Wed, 29 Jul 2020 03:17:39 +0200,
Luis Chamberlain wrote:
> 
> Long ago Takashi had some points about this strategy breaking
> compressed file use. Was that considered?

As long as I read the patch, it tries to skip both the compressed and
the fallback loading when FW_OPT_PARTIAL is set, which is good.

However...

> > @@ -771,18 +805,20 @@ _request_firmware(const struct firmware **firmware_p, const char *name,
> >  	}
> >  
> >  	ret = _request_firmware_prepare(&fw, name, device, buf, size,
> > -					opt_flags);
> > +					offset, opt_flags);
> >  	if (ret <= 0) /* error or already assigned */
> >  		goto out;
> >  
> >  	ret = fw_get_filesystem_firmware(device, fw->priv, "", NULL);
> > -#ifdef CONFIG_FW_LOADER_COMPRESS
> > -	if (ret == -ENOENT)
> > +
> > +	/* Only full reads can support decompression, platform, and sysfs. */
> > +	if (!(opt_flags & FW_OPT_PARTIAL))
> > +		nondirect = true;
> > +
> > +	if (ret == -ENOENT && nondirect)
> >  		ret = fw_get_filesystem_firmware(device, fw->priv, ".xz",
> >  						 fw_decompress_xz);
> > -#endif

... by dropping this ifdef, the fw loader would try to access *.xz
file unnecessarily even if CONFIG_FW_LOADER_COMPRESS is disabled.


thanks,

Takashi