Messages in this thread | | | Date | Mon, 3 Oct 2022 13:29:18 +0200 | From | Vincent Whitchurch <> | Subject | Re: [PATCH v2 2/4] spi: Fix cache corruption due to DMA/PIO overlap |
| |
On Fri, Sep 30, 2022 at 02:10:28PM +0200, Robin Murphy wrote: > That said, maybe this is something that's better to catch than to paper > over? Arguably the real bug here is that spi_unmap_buf() and the new > sync functions should use the same "{tx,rx}_buf != NULL" condition that > spi_map_buf() used for the DMA mapping decision in the first place.
The "{tx,rx}_buf != NULL" condition would not sufficient on its own; the call to ->can_dma() is also part of the condition. __spi_unmap_msg() already does the ->can_dma() call even though it checks for the orig_nents != 0 condition instead of the tx,rx_buf != NULL, but I omitted that call in the new sync functions, incorrectly believing it to be redundant.
It looks like __spi_unmap_msg() would have triggered a similar crash even before this patch, if a client had reused an xfer with both rx and tx the first time, and only one of them enabled the next time around (and with ->can_dma() returning true both times). Testing the {tx,rx}_buf instead of sgt->orig_nents would have avoided that, as you say.
| |