spi: Ensure that sg_table won't be used after being freed

[ Upstream commit 8e9204cddcc3fea9affcfa411715ba4f66e97587 ]

SPI code checks for non-zero sgt->orig_nents to determine if the buffer
has been DMA-mapped. Ensure that sg_table is really zeroed after free to
avoid potential NULL pointer dereference if the given SPI xfer object is
reused again without being DMA-mapped.

Fixes: 0c17ba73c08f ("spi: Fix cache corruption due to DMA/PIO overlap")
Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
Link: https://lore.kernel.org/r/20220930113408.19720-1-m.szyprowski@samsung.com
Signed-off-by: Mark Brown <broonie@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c
index 556d65a..06dd1be 100644 (file)
--- a/drivers/spi/spi.c
+++ b/drivers/spi/spi.c
@@ -1007,6 +1007,8 @@ void spi_unmap_buf(struct spi_controller *ctlr, struct device *dev,
        if (sgt->orig_nents) {
                dma_unmap_sg(dev, sgt->sgl, sgt->orig_nents, dir);
                sg_free_table(sgt);
+               sgt->orig_nents = 0;
+               sgt->nents = 0;
        }
 }