MdeModulePkg: UsbNetwork: fix Ethernet functional descriptor processing

This patch fixes wrong condition because of UINT16 value to integer
promotion. NumberMcFilters is UINT16 value, so when bitwise shift operator
applied to small integer type, the operation is preceded by integral
promotion. This is described in MISRA-C:2004 guideline as Rule 10.5:
"If the bitwise operators ~ and << are applied to an operand of underlying
type unsigned char or unsigned short, the result shall be immediately cast
to the underlying type of the operand."

A simple fix for this issue would be the following:
  if ((UINT16)(UsbEthFunDescriptor.NumberMcFilters << 1) == 0)

But this patch proposes to use bitwise AND operation with a proper bit mask
rather than shifting to prevent similar mistakes in future.

Cc: Richard Ho <richardho@ami.com>
Cc: Rebecca Cran <rebecca@bsdio.com>
Signed-off-by: Mike Maslenkin <mike.maslenkin@gmail.com>

1 files changed, 1 insertions, 1 deletions

diff --git a/MdeModulePkg/Bus/Usb/UsbNetwork/UsbCdcEcm/UsbEcmFunction.c b/MdeModulePkg/Bus/Usb/UsbNetwork/UsbCdcEcm/UsbEcmFunction.c
index 63003e07ff..29f4508a38 100644
--- a/MdeModulePkg/Bus/Usb/UsbNetwork/UsbCdcEcm/UsbEcmFunction.c
+++ b/MdeModulePkg/Bus/Usb/UsbNetwork/UsbCdcEcm/UsbEcmFunction.c
@@ -628,7 +628,7 @@ SetUsbEthMcastFilter (
     return Status;

   }

 

-  if ((UsbEthFunDescriptor.NumberMcFilters << 1) == 0) {

+  if ((UsbEthFunDescriptor.NumberMcFilters & MAC_FILTERS_MASK) == 0) {

     return EFI_UNSUPPORTED;

   }