Re: [edk2-devel] [PATCH 1/2] MdeModulePkg/Bus/Ata/AtaAtapiPassThru: Fix SIGN_EXTENSION Coverity issue

[Ranbir Singh <rsingh@ventanamicro.com>]

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Please read the Coverity report attached in BZ 4204 for more details on
sign-extension issue.

The data types of logic_sector_size_hi and logic_sector_size_lo are UINT16
and Isn't the return type of *sizeof* already unsigned ?

Now I have no means to run Coverity and test further changes.
Anyway, my understanding back then was that the sign-extension was
primarily happening because of the 16 bits left shift operation. I did test
the patch for coverity warning resolution back in Jan'23 which went off.


On Mon, Jun 5, 2023 at 4:28 AM Ard Biesheuvel <ardb@kernel.org> wrote:

> On Fri, 2 Jun 2023 at 21:42, Ranbir Singh <rsingh@ventanamicro.com> wrote:
> >
> > From: Ranbir Singh <Ranbir.Singh3@Dell.com>
> >
> > Line number 1348 does contain a typecast with UINT32, but it is after
> > all the operations (16-bit left shift followed by OR'ing) are over.
> > To avoid any SIGN_EXTENSION, typecast the intermediate result after
> > 16-bit left shift operation immediately with UINT32.
> >
>
> What is wrong with sign extension?
>
> > Cc: Hao A Wu <hao.a.wu@intel.com>
> > Cc: Ray Ni <ray.ni@intel.com>
> > REF: https://bugzilla.tianocore.org/show_bug.cgi?id=4204
> > Signed-off-by: Ranbir Singh <Ranbir.Singh3@Dell.com>
> > ---
> >  MdeModulePkg/Bus/Ata/AtaAtapiPassThru/AtaAtapiPassThru.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/MdeModulePkg/Bus/Ata/AtaAtapiPassThru/AtaAtapiPassThru.c
> b/MdeModulePkg/Bus/Ata/AtaAtapiPassThru/AtaAtapiPassThru.c
> > index 50406fe0270d..70c4ca27dc68 100644
> > --- a/MdeModulePkg/Bus/Ata/AtaAtapiPassThru/AtaAtapiPassThru.c
> > +++ b/MdeModulePkg/Bus/Ata/AtaAtapiPassThru/AtaAtapiPassThru.c
> > @@ -1345,7 +1345,7 @@ AtaPassThruPassThru (
> >      // Check logical block size
> >      //
> >      if ((IdentifyData->AtaData.phy_logic_sector_support & BIT12) != 0) {
> > -      BlockSize = (UINT32)(((IdentifyData->AtaData.logic_sector_size_hi
> << 16) | IdentifyData->AtaData.logic_sector_size_lo) * sizeof (UINT16));
> > +      BlockSize = (((UINT32)(IdentifyData->AtaData.logic_sector_size_hi
> << 16) | IdentifyData->AtaData.logic_sector_size_lo) * sizeof (UINT16));
>
>
> The outer parens are now redundant, which means you're assigning
> something to BlockSize whose type is based on the type of <something>
> * sizeof(UINT16), which is unsigned long not unsigned int, so this
> will produce a truncation warning on some compilers.
>
> If you want to suppress the coverity warning without introducing new
> ones, better to cast the sizeof() to (UINT32).
>

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