MdeModulePkg/Bus/Pci: Fix Descriptor Misalignment in USB Config Handling #6442
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The issue with locating the expected interface and endpoint descriptors arises because `configDesc` (USB_CONFIG_DESCRIPTOR) and `IfDesc` (USB_INTERFACE_DESCRIPTOR) are incremented by structure size rather than by actual descriptor length. Specifically: - `configDesc` should be incremented by its actual length. - `IfDesc` should be incremented by its actual length. This incorrect increment causes misalignment, preventing access to the subsequent interface and endpoint descriptors. [Suggested Solution] Update the code to increment the pointers by the actual descriptor lengths, ensuring proper access to all descriptors in the USB configuration. Signed-off-by: Aniket Surekar <[email protected]>
| @@ -2848,7 +2848,7 @@ XhcInitializeEndpointContext ( | |||
| MaxDci = 1; | |||
| } | |||
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| EpDesc = (USB_ENDPOINT_DESCRIPTOR *)(IfDesc + 1); | |||
| EpDesc = (USB_ENDPOINT_DESCRIPTOR *)((UINTN)IfDesc + IfDesc->Length); | |||
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Since IfDesc and ConfigDesc are pointer values, it would be better to type cast to another pointer type such as UINT8 * instead of an integer type of UINTN.
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Yes, I had a similar thought, but another file with existing code uses UINTN typecasting, so I kept it the same to maintain consistency. I referenced some of the existing code in edk2/MdeModulePkg/Bus/Pci/XhciDxe/XhciSched.c:
XhcInitializeEndpointContext() API: lines 2854, 2858, 2935, 2993, 3008
XhcInitializeEndpointContext64() API: lines 3057, 3061, 3138, 3196, 3211 And so on....
Similarly, in edk2/MdeModulePkg/Bus/Pci/XhciPei/XhciSched.c:
XhcPeiSetConfigCmd API: lines 1765, 1833, 1880, 1895
XhcPeiSetConfigCmd64 API: lines 1991, 2060, 2107, 2124 And so on....
For uniformity, I chose to retain the same typecasting.
The issue with locating the expected interface and endpoint descriptors
arises because configDesc (USB_CONFIG_DESCRIPTOR) and IfDesc
(USB_INTERFACE_DESCRIPTOR) are incremented by structure size rather than
by actual descriptor length.
Specifically:
configDesc should be incremented by its actual length.
IfDesc should be incremented by its actual length.
This incorrect increment causes misalignment, preventing access to the
subsequent interface and endpoint descriptors.
[Suggested Solution]
Update the code to increment the pointers by the actual descriptor lengths,
ensuring proper access to all descriptors in the USB configuration.
Bugzilla ID 4856