[U-Boot] [PATCH] mmc: cat u8 to u64 to avoid unexpected error

[Tom Rini]

On Tue, Sep 13, 2016 at 04:27:57PM +0800, Haibo Chen wrote:

> Suspicious implicit sign extension exist. ext_csd[] is defined
> as "u8", capacity is defined as u64, so u8 is promoted to signed
> int first int the "|" expersion, then the sign extended to u64.
> if the tmp sign value is largeer than 0x7fffffff, after the sign
> extension, the upper bits of the result will all be 1.
> Thanks to coverity <http://www.coverity.com>
> 
> e.g.
> 	u8  data_8;
> 	u64 data_64;
> 
> 	data_8 = 0x80;
> 	data_64 = data_8 << 24; //0xffffffff80000000
> 	data_64 = ((u64)data_8) << 24;  //0x80000000
> 
> Signed-off-by: Haibo Chen <haibo.chen at nxp.com>

Please add a 'Reported-by: Coverity' and you can include the CID if you
like.

> ---
>  drivers/mmc/mmc.c | 8 ++++----
>  1 file changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/mmc/mmc.c b/drivers/mmc/mmc.c
> index 43ea0bb..c1d1dc6 100644
> --- a/drivers/mmc/mmc.c
> +++ b/drivers/mmc/mmc.c
> @@ -1176,10 +1176,10 @@ static int mmc_startup(struct mmc *mmc)
>  			 * ext_csd's capacity is valid if the value is more
>  			 * than 2GB
>  			 */
> -			capacity = ext_csd[EXT_CSD_SEC_CNT] << 0
> -					| ext_csd[EXT_CSD_SEC_CNT + 1] << 8
> -					| ext_csd[EXT_CSD_SEC_CNT + 2] << 16
> -					| ext_csd[EXT_CSD_SEC_CNT + 3] << 24;
> +			capacity = ((u64)ext_csd[EXT_CSD_SEC_CNT]) << 0
> +					| ((u64)ext_csd[EXT_CSD_SEC_CNT + 1]) << 8
> +					| ((u64)ext_csd[EXT_CSD_SEC_CNT + 2]) << 16
> +					| ((u64)ext_csd[EXT_CSD_SEC_CNT + 3]) << 24;
>  			capacity *= MMC_MAX_BLOCK_LEN;
>  			if ((capacity >> 20) > 2 * 1024)
>  				mmc->capacity_user = capacity;

Can't we just move capacity down to a u8 instead?  Thanks!

-- 
Tom
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