linux-kernel - [PATCH] spi: Ensure that sg_table won't be used after being freed

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Message-Id: <20220930113408.19720-1-m.szyprowski@samsung.com>
Date:   Fri, 30 Sep 2022 13:34:08 +0200
From:   Marek Szyprowski <m.szyprowski@...sung.com>
To:     linux-spi@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:     Marek Szyprowski <m.szyprowski@...sung.com>,
        Vincent Whitchurch <vincent.whitchurch@...s.com>,
        Mark Brown <broonie@...nel.org>
Subject: [PATCH] spi: Ensure that sg_table won't be used after being freed

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@...sung.com>
---
 drivers/spi/spi.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c
index 44e4352d948b..5f9aedd1f0b6 100644
--- a/drivers/spi/spi.c
+++ b/drivers/spi/spi.c
@@ -1102,6 +1102,8 @@ static void spi_unmap_buf_attrs(struct spi_controller *ctlr,
 	if (sgt->orig_nents) {
 		dma_unmap_sgtable(dev, sgt, dir, attrs);
 		sg_free_table(sgt);
+		sgt->orig_nents = 0;
+		sgt->nents = 0;
 	}
 }
 
-- 
2.17.1