[PATCH net-next] ixgbe: Use struct_size() helper

[PATCH net-next] ixgbe: Use struct_size() helper

[Gustavo A. R. Silva]

One of the more common cases of allocation size calculations is finding
the size of a structure that has a zero-sized array at the end, along
with memory for some number of elements for that array. For example:

struct foo {
    int stuff;
    struct boo entry[];
};

size = sizeof(struct foo) + count * sizeof(struct boo);
instance = kzalloc(size, GFP_KERNEL);

Instead of leaving these open-coded and prone to type mistakes, we can
now use the new struct_size() helper:

instance = kzalloc(struct_size(instance, entry, count), GFP_KERNEL);

Notice that, in this case, variable size is not necessary, hence
it is removed.

This code was detected with the help of Coccinelle.

Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
---
 drivers/net/ethernet/intel/ixgbe/ixgbe_lib.c | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/drivers/net/ethernet/intel/ixgbe/ixgbe_lib.c b/drivers/net/ethernet/intel/ixgbe/ixgbe_lib.c
index 62e6499e4146..cc3196ae5aea 100644
--- a/drivers/net/ethernet/intel/ixgbe/ixgbe_lib.c
+++ b/drivers/net/ethernet/intel/ixgbe/ixgbe_lib.c
@@ -836,12 +836,10 @@ static int ixgbe_alloc_q_vector(struct ixgbe_adapter *adapter,
 	struct ixgbe_ring *ring;
 	int node = NUMA_NO_NODE;
 	int cpu = -1;
-	int ring_count, size;
+	int ring_count;
 	u8 tcs = adapter->hw_tcs;
 
 	ring_count = txr_count + rxr_count + xdp_count;
-	size = sizeof(struct ixgbe_q_vector) +
-	       (sizeof(struct ixgbe_ring) * ring_count);
 
 	/* customize cpu for Flow Director mapping */
 	if ((tcs <= 1) && !(adapter->flags & IXGBE_FLAG_SRIOV_ENABLED)) {
@@ -855,9 +853,11 @@ static int ixgbe_alloc_q_vector(struct ixgbe_adapter *adapter,
 	}
 
 	/* allocate q_vector and rings */
-	q_vector = kzalloc_node(size, GFP_KERNEL, node);
+	q_vector = kzalloc_node(struct_size(q_vector, ring, ring_count),
+				GFP_KERNEL, node);
 	if (!q_vector)
-		q_vector = kzalloc(size, GFP_KERNEL);
+		q_vector = kzalloc(struct_size(q_vector, ring, ring_count),
+				   GFP_KERNEL);
 	if (!q_vector)
 		return -ENOMEM;
 
-- 
2.20.1

Re: [PATCH net-next] ixgbe: Use struct_size() helper

[David Miller]

From: "Gustavo A. R. Silva" <gustavo@embeddedor.com>
Date: Thu, 7 Feb 2019 22:22:58 -0600

> One of the more common cases of allocation size calculations is finding
> the size of a structure that has a zero-sized array at the end, along
> with memory for some number of elements for that array. For example:
> 
> struct foo {
>     int stuff;
>     struct boo entry[];
> };
> 
> size = sizeof(struct foo) + count * sizeof(struct boo);
> instance = kzalloc(size, GFP_KERNEL);
> 
> Instead of leaving these open-coded and prone to type mistakes, we can
> now use the new struct_size() helper:
> 
> instance = kzalloc(struct_size(instance, entry, count), GFP_KERNEL);
> 
> Notice that, in this case, variable size is not necessary, hence
> it is removed.
> 
> This code was detected with the help of Coccinelle.
> 
> Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>

Applied.