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dcd_nrf5x: ISO OUT handling #1946

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kasjer
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@kasjer kasjer commented Mar 10, 2023

For incoming ISO OUT packets it was possible to start DMA from endpoint to RAM before transfer was started resulting in unrelated memory corruption.
This is scenario that causes memory corruption:

  • ISO OUT packet is received
  • Packet is transferred by DMA to transfer buffer
  • xfer->started is cleared and xfer->buffer is updated as it is in every case
  • Application takes to long to handle it (it happens when debugger is connected breakpoint is hit slowing down software).
  • Next ISO OUT packet arrives At this point there was no check if transfer was started and packet was copied by DMA to location beyond previous data, possibly overwriting unrelated memory.

This solves the issue by checking that transfer was started and there is buffer ready for incoming packet.

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For incoming ISO OUT packets it was possible to start
DMA from endpoint to RAM before transfer was started
resulting in unrelated memory corruption.
This is scenario that causes memory corruption:
- ISO OUT packet is received
- Packet is transferred by DMA to transfer buffer
- xfer->started is cleared and xfer->buffer is updated as
  it is in every case
- Application takes to long to handle it (it happens when debugger
  is connected breakpoint is hit slowing down software).
- Next ISO OUT packet arrives
At this point there was no check if transfer was started and packet
was copied by DMA to location beyond previous data, possibly overwriting
unrelated memory.

This solves the issue by checking that transfer was
started and there is buffer ready for incoming packet.
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@hathach hathach left a comment

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superb! thank you for yet another race condition with nrf. I guess this never ends :)

@hathach hathach merged commit b5b2fad into hathach:master Mar 11, 2023
@kasjer kasjer deleted the kasjer/nrf5x-fix-iso-memory-corruption branch March 13, 2023 09:26
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2 participants