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Verify frame length when handling CRSF_FRAMETYPE_MSP_REQ/CRSF_FRAMETYPE_MSP_WRITE #11210

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Verify frame length when handling CRSF_FRAMETYPE_MSP_REQ/CRSF_FRAMETYPE_MSP_WRITE #11210

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10 changes: 7 additions & 3 deletions src/main/rx/crsf.c
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Original file line number Diff line number Diff line change
Expand Up @@ -173,9 +173,13 @@ STATIC_UNIT_TESTED void crsfDataReceive(uint16_t c, void *rxCallbackData)
#if defined(USE_MSP_OVER_TELEMETRY)
case CRSF_FRAMETYPE_MSP_REQ:
case CRSF_FRAMETYPE_MSP_WRITE: {
uint8_t *frameStart = (uint8_t *)&crsfFrame.frame.payload + CRSF_FRAME_ORIGIN_DEST_SIZE;
if (bufferCrsfMspFrame(frameStart, crsfFrame.frame.frameLength - 4)) {
crsfScheduleMspResponse(crsfFrame.frame.payload[1]);
if (crsfFrame.frame.frameLength >= 4) {
uint8_t *frameStart = (uint8_t *)&crsfFrame.frame.payload + CRSF_FRAME_ORIGIN_DEST_SIZE;
if (bufferCrsfMspFrame(frameStart, crsfFrame.frame.frameLength - 4)) {
Comment on lines +176 to +178
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Copilot AI Jan 10, 2026

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The magic number 4 should be replaced with the named constant CRSF_FRAME_LENGTH_EXT_TYPE_CRC for better code maintainability and clarity. This constant represents the overhead for extended frames (Type + Origin + Destination + CRC).

Suggested change
if (crsfFrame.frame.frameLength >= 4) {
uint8_t *frameStart = (uint8_t *)&crsfFrame.frame.payload + CRSF_FRAME_ORIGIN_DEST_SIZE;
if (bufferCrsfMspFrame(frameStart, crsfFrame.frame.frameLength - 4)) {
if (crsfFrame.frame.frameLength >= CRSF_FRAME_LENGTH_EXT_TYPE_CRC) {
uint8_t *frameStart = (uint8_t *)&crsfFrame.frame.payload + CRSF_FRAME_ORIGIN_DEST_SIZE;
if (bufferCrsfMspFrame(frameStart, crsfFrame.frame.frameLength - CRSF_FRAME_LENGTH_EXT_TYPE_CRC)) {

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crsfScheduleMspResponse(crsfFrame.frame.payload[1]);
}
} else {
crsfFrameDone = false;
}
break;
}
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