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Subject: Re: [PATCH 1/7] fs: introduce kernel_pread_file* support
To:     Takashi Iwai <tiwai@suse.de>
Cc:     Luis Chamberlain <mcgrof@kernel.org>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        David Brown <david.brown@linaro.org>,
        Alexander Viro <viro@zeniv.linux.org.uk>,
        Shuah Khan <shuah@kernel.org>, bjorn.andersson@linaro.org,
        Shuah Khan <skhan@linuxfoundation.org>,
        Arnd Bergmann <arnd@arndb.de>,
        "Rafael J . Wysocki" <rafael@kernel.org>,
        linux-kernel@vger.kernel.org, linux-arm-msm@vger.kernel.org,
        linux-fsdevel@vger.kernel.org,
        BCM Kernel Feedback <bcm-kernel-feedback-list@broadcom.com>,
        Olof Johansson <olof@lixom.net>,
        Andrew Morton <akpm@linux-foundation.org>,
        Dan Carpenter <dan.carpenter@oracle.com>,
        Colin Ian King <colin.king@canonical.com>,
        Kees Cook <keescook@chromium.org>,
        linux-kselftest@vger.kernel.org, Mimi Zohar <zohar@linux.ibm.com>
References: <20190822192451.5983-1-scott.branden@broadcom.com>
 <20190822192451.5983-2-scott.branden@broadcom.com>
 <s5hsgpsqd49.wl-tiwai@suse.de>
From:   Scott Branden <scott.branden@broadcom.com>
Message-ID: <5227a1bb-52e5-d547-2650-b06bee259012@broadcom.com>
Date:   Fri, 23 Aug 2019 12:55:30 -0700
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Hi Takashi

On 2019-08-23 5:29 a.m., Takashi Iwai wrote:
> On Thu, 22 Aug 2019 21:24:45 +0200,
> Scott Branden wrote:
>> Add kernel_pread_file* support to kernel to allow for partial read
>> of files with an offset into the file.  Existing kernel_read_file
>> functions call new kernel_pread_file functions with offset=0 and
>> flags=KERNEL_PREAD_FLAG_WHOLE.
> Would this change passes the security check like ima?
> I thought security_kernel_post_read_file() checks the whole content
> for calculating the hash...

It passes the fw_run_tests.sh.  How do you test the firmware loader 
passes this security check?


What exactly does this ima do?  How do you enable/disable using it?

Any reasonable device would check the integrity of the firmware image 
being loaded to it.

And, if part of a security model, authenticate the image.

Whatever security check you are referring to is not needed by 
request_firmware_into_buf when loading

a partial file into a buffer.


>
>
> thanks,
>
> Takashi