BLEManagerImpl may have MTU overflow its storage

[bzbarsky-apple]

Problem

In src/platform/ESP32/BLEManagerImpl.cpp we have this line in BLEManagerImpl::HandleGATTCommEvent:

conState->MTU = param->mtu.mtu;

The right-hand side is a uint16_t. The left-hand side is a 10-bit bitfield. There seems to be no check that the value on the right will fit on the left, nor any explanation for why a check is not needed.

Proposed Solution

Either introduce a check or add an explanation for why it's not needed.

@sagar-apple it looks like you might know something about this code?

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[sagar-apple]

@shana-apple amd @vivien-apple are probably more familiar with this. I can look if they're unable.

[bzbarsky-apple]

src/platform/EFR32/BLEManagerImpl.cpp has a similar issue in BLEManagerImpl::UpdateMtu.

[andy31415]

This looks like platform specific code - re-assigned to platform owner.

[dhrishi]

nor any explanation for why a check is not needed.

@bzbarsky-apple As per the BLE specification, the maximum MTU value can be 517 bytes. This can be accomodated in 10 bits. Good enough to close this?

[bzbarsky-apple]

Good enough, but would be even better with a comment. ;)