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

[Jaehoon Chung]

On 09/19/2016 02:53 AM, Tom Rini wrote:
> 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.

I think cid doesn't need to change type.

> 
>> ---
>>  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!

Maybe not to move down to a u8..because it's displayed the real capacity for storage.

And i wonder that coverity didn't report about the line 1294?

Best Regards,
Jaehoon Chung

> 
> 
> 
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