[PATCH 01/13] firmware_loader: EFI firmware loader must handle pre-allocated buffer

[Scott Branden]

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 at vger.kernel.org
> Signed-off-by: Kees Cook <keescook at chromium.org>
Acked-by: Scott Branden <scott.branden at 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;
>