[PATCH] dmaengine: pxa_dma: Prefer struct_size over open coded arithmetic

As noted in the "Deprecated Interfaces, Language Features, Attributes,
and Conventions" documentation [1], size calculations (especially
multiplication) should not be performed in memory allocator (or similar)
function arguments due to the risk of them overflowing. This could lead
to values wrapping around and a smaller allocation being made than the
caller was expecting. Using those allocations could lead to linear
overflows of heap memory and other misbehaviors.

So, use the struct_size() helper to do the arithmetic instead of the
argument "size + count * size" in the kzalloc() function.

[1] https://www.kernel.org/doc/html/latest/process/deprecated.html#open-coded-arithmetic-in-allocator-arguments

Signed-off-by: Len Baker <redacted>
---
 drivers/dma/pxa_dma.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/drivers/dma/pxa_dma.c b/drivers/dma/pxa_dma.c
index 4a2a796e348c..52d04641e361 100644
--- a/drivers/dma/pxa_dma.c
+++ b/drivers/dma/pxa_dma.c

@@ -742,8 +742,7 @@ pxad_alloc_desc(struct pxad_chan *chan, unsigned int nb_hw_desc)
 	dma_addr_t dma;
 	int i;

-	sw_desc = kzalloc(sizeof(*sw_desc) +
-			  nb_hw_desc * sizeof(struct pxad_desc_hw *),
+	sw_desc = kzalloc(struct_size(sw_desc, hw_desc, nb_hw_desc),
 			  GFP_NOWAIT);
 	if (!sw_desc)
 		return NULL;
--

2.25.1


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On 9/18/21 05:40, Len Baker wrote:

As noted in the "Deprecated Interfaces, Language Features, Attributes,
and Conventions" documentation [1], size calculations (especially
multiplication) should not be performed in memory allocator (or similar)
function arguments due to the risk of them overflowing. This could lead
to values wrapping around and a smaller allocation being made than the
caller was expecting. Using those allocations could lead to linear
overflows of heap memory and other misbehaviors.

So, use the struct_size() helper to do the arithmetic instead of the
argument "size + count * size" in the kzalloc() function.

[1] https://www.kernel.org/doc/html/latest/process/deprecated.html#open-coded-arithmetic-in-allocator-arguments

Signed-off-by: Len Baker <redacted>

Reviewed-by: Gustavo A. R. Silva <gustavoars@kernel.org>

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On Mon, Sep 20, 2021 at 07:00:58PM -0500, Gustavo A. R. Silva wrote:

On 9/18/21 05:40, Len Baker wrote:

quoted

As noted in the "Deprecated Interfaces, Language Features, Attributes,
and Conventions" documentation [1], size calculations (especially
multiplication) should not be performed in memory allocator (or similar)
function arguments due to the risk of them overflowing. This could lead
to values wrapping around and a smaller allocation being made than the
caller was expecting. Using those allocations could lead to linear
overflows of heap memory and other misbehaviors.

So, use the struct_size() helper to do the arithmetic instead of the
argument "size + count * size" in the kzalloc() function.

[1] https://www.kernel.org/doc/html/latest/process/deprecated.html#open-coded-arithmetic-in-allocator-arguments

Signed-off-by: Len Baker <redacted>

Reviewed-by: Gustavo A. R. Silva <gustavoars@kernel.org>

I'm taking this in my -next tree.

Thanks
--
Gustavo

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