linux-kernel - Re: [PATCH v2 2/2] firmware_class: perform new LSM checks

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Date:	Tue, 22 Jul 2014 08:55:03 +0200
From:	Takashi Iwai <tiwai@...e.de>
To:	Kees Cook <keescook@...omium.org>
Cc:	linux-kernel@...r.kernel.org,
	James Morris <james.l.morris@...cle.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Ming Lei <ming.lei@...onical.com>,
	linux-security-module@...r.kernel.org
Subject: Re: [PATCH v2 2/2] firmware_class: perform new LSM checks

At Mon, 21 Jul 2014 12:06:41 -0700,
Kees Cook wrote:
> 
> This attaches LSM hooks to the existing firmware loading interfaces:
> filesystem-found firmware and demand-loaded blobs.
> 
> Signed-off-by: Kees Cook <keescook@...omium.org>
> Acked-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
> ---
>  drivers/base/firmware_class.c |   16 ++++++++++++++--
>  1 file changed, 14 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/base/firmware_class.c b/drivers/base/firmware_class.c
> index d276e33880be..7399bab71ced 100644
> --- a/drivers/base/firmware_class.c
> +++ b/drivers/base/firmware_class.c
> @@ -28,6 +28,7 @@
>  #include <linux/suspend.h>
>  #include <linux/syscore_ops.h>
>  #include <linux/reboot.h>
> +#include <linux/security.h>
>  
>  #include <generated/utsrelease.h>
>  
> @@ -308,12 +309,17 @@ static int fw_read_file_contents(struct file *file, struct firmware_buf *fw_buf)
>  	if (rc != size) {
>  		if (rc > 0)
>  			rc = -EIO;
> -		vfree(buf);
> -		return rc;
> +		goto fail;
>  	}
> +	rc = security_kernel_fw_from_file(file, buf, size);
> +	if (rc)
> +		goto fail;
>  	fw_buf->data = buf;
>  	fw_buf->size = size;
>  	return 0;
> +fail:
> +	vfree(buf);
> +	return rc;
>  }
>  
>  static int fw_get_filesystem_firmware(struct device *device,
> @@ -640,6 +646,12 @@ static ssize_t firmware_loading_store(struct device *dev,
>  		break;
>  	case 0:
>  		if (test_bit(FW_STATUS_LOADING, &fw_buf->status)) {
> +			if (security_kernel_fw_from_file(NULL, fw_buf->data,
> +							 fw_buf->size)) {
> +				fw_load_abort(fw_priv);
> +				break;
> +			}
>  			set_bit(FW_STATUS_DONE, &fw_buf->status);
>  			clear_bit(FW_STATUS_LOADING, &fw_buf->status);

security_kernel_fw_from_file() should be called after
fw_map_pages_buf() call (that is found after these lines).
Otherwise fw_buf->buf won't contain a valid buffer pointer.


Takashi
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