From: Andy Shevchenko Date: Wed, 29 May 2024 15:42:35 +0000 (-0400) Subject: spi: Assign dummy scatterlist to unidirectional transfers X-Git-Tag: v6.10-rc2~16^2~1 X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=9dedabe95b49ec9b0d16ce8f0ed1f9a12dd4a040;p=thirdparty%2Flinux.git spi: Assign dummy scatterlist to unidirectional transfers Commit 8cc3bad9d9d6 ("spi: Remove unneded check for orig_nents") introduced a regression: unmapped data could now be passed to the DMA APIs, resulting in null pointer dereferences. Commit 9f788ba457b4 ("spi: Don't mark message DMA mapped when no transfer in it is") and commit da560097c056 ("spi: Check if transfer is mapped before calling DMA sync APIs") addressed the problem, but only partially. Unidirectional transactions will still result in null pointer dereference. To prevent that from happening, assign a dummy scatterlist when no data is mapped, so that the DMA API can be called and not result in a null pointer dereference. Signed-off-by: Andy Shevchenko Reported-by: Neil Armstrong Closes: https://lore.kernel.org/r/8ae675b5-fcf9-4c9b-b06a-4462f70e1322@linaro.org Reported-by: Nícolas F. R. A. Prado Closes: https://lore.kernel.org/all/d3679496-2e4e-4a7c-97ed-f193bd53af1d@notapiano Closes: https://lore.kernel.org/all/4748499f-789c-45a8-b50a-2dd09f4bac8c@notapiano Fixes: 8cc3bad9d9d6 ("spi: Remove unneded check for orig_nents") Tested-by: Nícolas F. R. A. Prado [nfraprado: wrote the commit message] Signed-off-by: Nícolas F. R. A. Prado Link: https://msgid.link/r/20240529-dma-oops-dummy-v1-1-bb43aacfb11b@collabora.com Signed-off-by: Mark Brown --- diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c index f94420858c224..9bc9fd10d538d 100644 --- a/drivers/spi/spi.c +++ b/drivers/spi/spi.c @@ -1220,6 +1220,11 @@ void spi_unmap_buf(struct spi_controller *ctlr, struct device *dev, spi_unmap_buf_attrs(ctlr, dev, sgt, dir, 0); } +/* Dummy SG for unidirect transfers */ +static struct scatterlist dummy_sg = { + .page_link = SG_END, +}; + static int __spi_map_msg(struct spi_controller *ctlr, struct spi_message *msg) { struct device *tx_dev, *rx_dev; @@ -1258,6 +1263,8 @@ static int __spi_map_msg(struct spi_controller *ctlr, struct spi_message *msg) attrs); if (ret != 0) return ret; + } else { + xfer->tx_sg.sgl = &dummy_sg; } if (xfer->rx_buf != NULL) { @@ -1271,6 +1278,8 @@ static int __spi_map_msg(struct spi_controller *ctlr, struct spi_message *msg) return ret; } + } else { + xfer->rx_sg.sgl = &dummy_sg; } } /* No transfer has been mapped, bail out with success */