Re: [edk2-devel] [PATCH v1 1/2] MdeModulePkg/Bus/Pci/UhciDxe: Fix BAD_SHIFT Coverity issue

["Wu, Hao A" <hao.a.wu@intel.com>]

> -----Original Message-----
> From: Ranbir Singh <rsingh@ventanamicro.com>
> Sent: Monday, July 17, 2023 7:39 PM
> To: devel@edk2.groups.io; rsingh@ventanamicro.com
> Cc: Wu, Hao A <hao.a.wu@intel.com>; Ni, Ray <ray.ni@intel.com>; Veeresh
> Sangolli <veeresh.sangolli@dellteam.com>
> Subject: [PATCH v1 1/2] MdeModulePkg/Bus/Pci/UhciDxe: Fix BAD_SHIFT
> Coverity issue
> 
> From: Ranbir Singh <Ranbir.Singh3@Dell.com>
> 
> The function UhciConvertPollRate has a check
> 
>     ASSERT (Interval != 0);
> 
> but this comes into play only in DEBUG mode. In Release mode, there is
> no handling if the Interval parameter value is ZERO. To avoid shifting
> by a negative amount later in the code flow in this undesirable case,
> it is better to handle it as well by simply returning ZERO.
> 
> REF: https://bugzilla.tianocore.org/show_bug.cgi?id=4211
> 
> Cc: Hao A Wu <hao.a.wu@intel.com>
> Cc: Ray Ni <ray.ni@intel.com>
> Co-authored-by: Veeresh Sangolli <veeresh.sangolli@dellteam.com>
> Signed-off-by: Ranbir Singh <Ranbir.Singh3@Dell.com>
> Signed-off-by: Ranbir Singh <rsingh@ventanamicro.com>
> ---
>  MdeModulePkg/Bus/Pci/UhciDxe/UhciSched.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/MdeModulePkg/Bus/Pci/UhciDxe/UhciSched.c
> b/MdeModulePkg/Bus/Pci/UhciDxe/UhciSched.c
> index c08f9496969b..8ddef4b68ccf 100644
> --- a/MdeModulePkg/Bus/Pci/UhciDxe/UhciSched.c
> +++ b/MdeModulePkg/Bus/Pci/UhciDxe/UhciSched.c
> @@ -214,6 +214,10 @@ UhciConvertPollRate (
> 
> 
>    ASSERT (Interval != 0);
> 
> 
> 
> +  if (Interval == 0) {
> 
> +    return 0;


Return 0 will cause further issues within UhciLinkQhToFrameList() &
UhciUnlinkQhFromFrameList() where the returned value is being used in the below
'for' statement:

for (Index = 0; Index < UHCI_FRAME_NUM; Index += Qh->Interval) {

My thought is to return 1 (i.e. 1 << 0) as if the minimum allowed value for
'Interval' (which is 1) is being passed into this UhciConvertPollRate function.

Best Regards,
Hao Wu


> 
> +  }
> 
> +
> 
>    //
> 
>    // Find the index (1 based) of the highest non-zero bit
> 
>    //
> 
> --
> 2.34.1



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