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

[Tom Rini]

On Tue, Sep 20, 2016 at 11:04:40AM +0900, Jaehoon Chung wrote:
> On 09/19/2016 08:30 PM, Tom Rini wrote:
> > On Mon, Sep 19, 2016 at 03:31:54PM +0900, Jaehoon Chung wrote:
> >> 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.
> > 
> > I mean the coverity CID :)  In the public coverity project it's 149300
> 
> Ah! I misunderstood CID as cid register. :)
> 
> > 
> >>
> >>>
> >>>> ---
> >>>>  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.
> > 
> > We could update those lines too?  It's just that one case right there,
> > yes?
> 
> If it's possible to calculate the correct capacity?

... I think?  I hadn't had my coffee yet when I did a quick compile test
this morning but it looks like all of the uses of capacity would fit
into a u8.  Someone should check and make a formal patch :)

-- 
Tom
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