Messages in this thread | | | Date | Wed, 25 Apr 2018 11:31:28 +0100 | From | Lee Jones <> | Subject | Re: [PATCH] rave-sp: Remove VLA |
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On Tue, 24 Apr 2018, Kees Cook wrote:
> On Mon, Apr 23, 2018 at 10:43 PM, Lee Jones <lee.jones@linaro.org> wrote: > > On Mon, 23 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@google.com> > >> --- > >> drivers/mfd/rave-sp.c | 11 +++++++++-- > >> 1 file changed, 9 insertions(+), 2 deletions(-) > >> > >> diff --git a/drivers/mfd/rave-sp.c b/drivers/mfd/rave-sp.c > >> index 5c858e784a89..99fa482419f9 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(length > sizeof(crc_calculated))) { > > > > Forgive me if I have this wrong (it's still very early here), but this > > doesn't leave any room for the payload? > > > > <-- length --> > > <ck len><- payload length -> > > [CK][CK][D][A][T][A] .. [64] > > > > It is my hope that length would always be larger than the size of the > > checksum, or else there would never be any data? > > > > Should this not be: > > > > if (unlikely(length > RAVE_SP_MAX_DATA_SIZE)) > > Oh, whoops, no, this should be: > > + if (unlikely(checksum_lengh > sizeof(crc_calculated))) { > > (To validate the VLA max size.)
That doesn't match the OP's error message though:
dev_warn(dev, "Dropping oversized frame\n");
Which I assume is designed to complement the existing warning:
if (unlikely(length <= checksum_length)) dev_warn(dev, "Dropping short frame\n");
-- Lee Jones [李琼斯] Linaro Services Technical Lead Linaro.org │ Open source software for ARM SoCs Follow Linaro: Facebook | Twitter | Blog
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