[PATCH 6/7][Focal/linux-azure] net: mana: Prefer struct_size over open coded arithmetic

Tim Gardner tim.gardner at canonical.com
Thu Oct 21 12:23:40 UTC 2021

From: Len Baker <len.baker at gmx.com>

BugLink: https://bugs.launchpad.net/bugs/1947859

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/v5.14/process/deprecated.html#open-coded-arithmetic-in-allocator-arguments

Signed-off-by: Len Baker <len.baker at gmx.com>
Reviewed-by: Haiyang Zhang <haiyangz at microsoft.com>
Signed-off-by: David S. Miller <davem at davemloft.net>
(cherry picked from commit f11ee2ad25b22c2ee587045dd6999434375532f7)
Signed-off-by: Tim Gardner <tim.gardner at canonical.com>
 drivers/net/ethernet/microsoft/mana/hw_channel.c | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/drivers/net/ethernet/microsoft/mana/hw_channel.c b/drivers/net/ethernet/microsoft/mana/hw_channel.c
index c1310ea1c216f..d5c485a6d2845 100644
--- a/drivers/net/ethernet/microsoft/mana/hw_channel.c
+++ b/drivers/net/ethernet/microsoft/mana/hw_channel.c
@@ -398,9 +398,7 @@ static int mana_hwc_alloc_dma_buf(struct hw_channel_context *hwc, u16 q_depth,
 	int err;
 	u16 i;
-	dma_buf = kzalloc(sizeof(*dma_buf) +
-			  q_depth * sizeof(struct hwc_work_request),
-			  GFP_KERNEL);
+	dma_buf = kzalloc(struct_size(dma_buf, reqs, q_depth), GFP_KERNEL);
 	if (!dma_buf)
 		return -ENOMEM;

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