On Wed, Oct 14, 2020 at 02:20:16PM -0700, Florian Fainelli wrote:
> In bcm2835_spi_remove(), spi_controller_unregister() will free the ctlr
> reference which will lead to an use after free in bcm2835_release_dma().
>
> To avoid this use after free, allocate the bcm2835_spi structure with a
> different lifecycle than the spi_controller structure such that we
> unregister the SPI controller, free up all the resources and finally let
> device managed allocations free the bcm2835_spi structure.
[...]
> - if (ctlr->dma_tx) {
> - dmaengine_terminate_sync(ctlr->dma_tx);
> + if (dma_tx) {
> + dmaengine_terminate_sync(dma_tx);
>
> if (bs->fill_tx_desc)
> dmaengine_desc_free(bs->fill_tx_desc);
>
> if (bs->fill_tx_addr)
> - dma_unmap_page_attrs(ctlr->dma_tx->device->dev,
> + dma_unmap_page_attrs(dma_tx->device->dev,
> bs->fill_tx_addr, sizeof(u32),
> DMA_TO_DEVICE,
> DMA_ATTR_SKIP_CPU_SYNC);
>
> - dma_release_channel(ctlr->dma_tx);
> - ctlr->dma_tx = NULL;
> + dma_release_channel(dma_tx);
> }
You must set ctlr->dma_tx and ctlr->dma_rx to NULL because the driver
checks their value in a couple of places.
E.g. bcm2835_spi_setup() checks ctlr->dma_rx.
Likewise, the error paths of bcm2835_dma_init() and bcm2835_spi_probe()
call bcm2835_dma_release() and the latter checks ctlr->dma_tx and
ctlr->dma_rx to determine whether DMA was set up, hence needs to be
torn down.
> + bs = devm_kzalloc(&pdev->dev, sizeof(*bs), GFP_KERNEL);
> + if (!bs)
> + return -ENOMEM;
> +
> ctlr = spi_alloc_master(&pdev->dev, ALIGN(sizeof(*bs),
> dma_get_cache_alignment()));
You can set the second argument to spi_alloc_master() to 0
to conserve memory.
Thanks,
Lukas
