[PATCH 14/21] dmaengine: stm32-mdma: Annotate struct stm32_mdma_device with __counted_by

Kees Cook
2023-08-18T00:00:09Z

Prepare for the coming implementation by GCC and Clang of the __counted_by
attribute. Flexible array members annotated with __counted_by can have
their accesses bounds-checked at run-time checking via CONFIG_UBSAN_BOUNDS
(for array indexing) and CONFIG_FORTIFY_SOURCE (for strcpy/memcpy-family
functions).

As found with Coccinelle[1], add __counted_by for struct stm32_mdma_device.
Additionally, since the element count member must be set before accessing
the annotated flexible array member, move its initialization earlier.

[1] https://github.com/kees/kernel-tools/blob/trunk/coccinelle/examples/counted_by.cocci

Cc: Vinod Koul <vkoul@kernel.org>
Cc: Maxime Coquelin <mcoquelin.stm32@gmail.com>
Cc: Alexandre Torgue <alexandre.torgue@foss.st.com>
Cc: dmaengine@vger.kernel.org
Cc: linux-stm32@st-md-mailman.stormreply.com
Cc: linux-arm-kernel@lists.infradead.org
Signed-off-by: Kees Cook <keescook@chromium.org>
---
drivers/dma/stm32-mdma.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/dma/stm32-mdma.c b/drivers/dma/stm32-mdma.c
index 926d6ecf1274..0c7d2295856e 100644
--- a/drivers/dma/stm32-mdma.c
+++ b/drivers/dma/stm32-mdma.c
@@ -256,7 +256,7 @@ struct stm32_mdma_device {
u32 nr_ahb_addr_masks;
u32 chan_reserved;
struct stm32_mdma_chan chan[STM32_MDMA_MAX_CHANNELS];
- u32 ahb_addr_masks[];
+ u32 ahb_addr_masks[] __counted_by(nr_ahb_addr_masks);
};

static struct stm32_mdma_device *stm32_mdma_get_dev(
@@ -1611,13 +1611,13 @@ static int stm32_mdma_probe(struct platform_device *pdev)
GFP_KERNEL);
if (!dmadev)
return -ENOMEM;
+ dmadev->nr_ahb_addr_masks = count;

dmadev->nr_channels = nr_channels;
dmadev->nr_requests = nr_requests;
device_property_read_u32_array(&pdev->dev, "st,ahb-addr-masks",
dmadev->ahb_addr_masks,
count);
- dmadev->nr_ahb_addr_masks = count;

dmadev->base = devm_platform_ioremap_resource(pdev, 0);
if (IS_ERR(dmadev->base))
--
2.34.1