linux-kernel - Re: [PATCH v2] rave-sp: Remove VLA

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Date:   Mon, 30 Apr 2018 06:48:37 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Lee Jones <lee.jones@...aro.org>
Cc:     Kyle Spiers <ksspiers@...gle.com>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] rave-sp: Remove VLA

On Mon, Apr 30, 2018 at 5:38 AM, Lee Jones <lee.jones@...aro.org> wrote:
> On Fri, 27 Apr 2018, Kyle Spiers wrote:
>
>> As part of the effort to remove VLAs from the kernel[1], this creates
>> constants for the checksum lengths of CCITT and 8B2C and changes
>> crc_calculated to be the maximum size of a checksum.
>>
>> https://lkml.org/lkml/2018/3/7/621
>>
>> Signed-off-by: Kyle Spiers <ksspiers@...gle.com>
>> ---
>>  drivers/mfd/rave-sp.c | 11 +++++++++--
>>  1 file changed, 9 insertions(+), 2 deletions(-)
>
> Applied, thanks.
>
> Kees, do you want me to add your Ack?

Sure!

Reviewed-by: Kees Cook <keescook@...omium.org>

Thanks!

-Kees

>
>> diff --git a/drivers/mfd/rave-sp.c b/drivers/mfd/rave-sp.c
>> index 5c858e784a89..4ce96b7137db 100644
>> --- a/drivers/mfd/rave-sp.c
>> +++ b/drivers/mfd/rave-sp.c
>> @@ -45,7 +45,9 @@
>>  #define RAVE_SP_DLE                  0x10
>>
>>  #define RAVE_SP_MAX_DATA_SIZE                64
>> -#define RAVE_SP_CHECKSUM_SIZE                2  /* Worst case scenario on RDU2 */
>> +#define RAVE_SP_CHECKSUM_8B2C                1
>> +#define RAVE_SP_CHECKSUM_CCITT               2
>> +#define RAVE_SP_CHECKSUM_SIZE                RAVE_SP_CHECKSUM_CCITT
>>  /*
>>   * We don't store STX, ETX and unescaped bytes, so Rx is only
>>   * DATA + CSUM
>> @@ -415,7 +417,12 @@ static void rave_sp_receive_frame(struct rave_sp *sp,
>>       const size_t payload_length  = length - checksum_length;
>>       const u8 *crc_reported       = &data[payload_length];
>>       struct device *dev           = &sp->serdev->dev;
>> -     u8 crc_calculated[checksum_length];
>> +     u8 crc_calculated[RAVE_SP_CHECKSUM_SIZE];
>> +
>> +     if (unlikely(checksum_length > sizeof(crc_calculated))) {
>> +             dev_warn(dev, "Checksum too long, dropping\n");
>> +             return;
>> +     }
>>
>>       print_hex_dump(KERN_DEBUG, "rave-sp rx: ", DUMP_PREFIX_NONE,
>>                      16, 1, data, length, false);
>
> --
> Lee Jones [李琼斯]
> Linaro Services Technical Lead
> Linaro.org │ Open source software for ARM SoCs
> Follow Linaro: Facebook | Twitter | Blog



-- 
Kees Cook
Pixel Security