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Subject: Re: [PATCH 01/13] firmware_loader: EFI firmware loader must handle
 pre-allocated buffer
To:     Kees Cook <keescook@chromium.org>
Cc:     stable@vger.kernel.org, Mimi Zohar <zohar@linux.ibm.com>,
        Matthew Wilcox <willy@infradead.org>,
        James Morris <jmorris@namei.org>,
        Luis Chamberlain <mcgrof@kernel.org>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        "Rafael J. Wysocki" <rafael@kernel.org>,
        Alexander Viro <viro@zeniv.linux.org.uk>,
        Jessica Yu <jeyu@kernel.org>,
        Dmitry Kasatkin <dmitry.kasatkin@gmail.com>,
        "Serge E. Hallyn" <serge@hallyn.com>,
        Casey Schaufler <casey@schaufler-ca.com>,
        "Eric W. Biederman" <ebiederm@xmission.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Matthew Garrett <matthewgarrett@google.com>,
        David Howells <dhowells@redhat.com>,
        Mauro Carvalho Chehab <mchehab+huawei@kernel.org>,
        Randy Dunlap <rdunlap@infradead.org>,
        "Joel Fernandes (Google)" <joel@joelfernandes.org>,
        KP Singh <kpsingh@google.com>, Dave Olsthoorn <dave@bewaar.me>,
        Hans de Goede <hdegoede@redhat.com>,
        Peter Jones <pjones@redhat.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Stephen Boyd <stephen.boyd@linaro.org>,
        Paul Moore <paul@paul-moore.com>,
        Stephen Smalley <stephen.smalley.work@gmail.com>,
        linux-security-module@vger.kernel.org,
        linux-integrity@vger.kernel.org, selinux@vger.kernel.org,
        linux-fsdevel@vger.kernel.org, kexec@lists.infradead.org,
        linux-kernel@vger.kernel.org
References: <20200717174309.1164575-1-keescook@chromium.org>
 <20200717174309.1164575-2-keescook@chromium.org>
From:   Scott Branden <scott.branden@broadcom.com>
Message-ID: <d8aa2da5-d678-811a-9c28-b372b5491d4b@broadcom.com>
Date:   Fri, 17 Jul 2020 12:08:14 -0700
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On 2020-07-17 10:42 a.m., Kees Cook wrote:
> The EFI platform firmware fallback would clobber any pre-allocated
> buffers. Instead, correctly refuse to reallocate when too small (as
> already done in the sysfs fallback), or perform allocation normally
> when needed.
>
> Fixes: e4c2c0ff00ec ("firmware: Add new platform fallback mechanism and firm ware_request_platform()")
> Cc: stable@vger.kernel.org
> Signed-off-by: Kees Cook <keescook@chromium.org>
Acked-by: Scott Branden <scott.branden@broadcom.com>
> ---
> To aid in backporting, this change is made before moving
> kernel_read_file() to separate header/source files.
> ---
>   drivers/base/firmware_loader/fallback_platform.c | 5 ++++-
>   1 file changed, 4 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/base/firmware_loader/fallback_platform.c b/drivers/base/firmware_loader/fallback_platform.c
> index cdd2c9a9f38a..685edb7dd05a 100644
> --- a/drivers/base/firmware_loader/fallback_platform.c
> +++ b/drivers/base/firmware_loader/fallback_platform.c
> @@ -25,7 +25,10 @@ int firmware_fallback_platform(struct fw_priv *fw_priv, u32 opt_flags)
>   	if (rc)
>   		return rc; /* rc == -ENOENT when the fw was not found */
>   
> -	fw_priv->data = vmalloc(size);
> +	if (fw_priv->data && size > fw_priv->allocated_size)
> +		return -ENOMEM;
> +	if (!fw_priv->data)
> +		fw_priv->data = vmalloc(size);
>   	if (!fw_priv->data)
>   		return -ENOMEM;
>