[PATCH net-next] igb: use struct_size() helper

[PATCH net-next] igb: 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 = alloc(size, GFP_KERNEL);

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

size = struct_size(instance, entry, count);

This code was detected with the help of Coccinelle.

Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
---
 drivers/net/ethernet/intel/igb/igb_main.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/net/ethernet/intel/igb/igb_main.c b/drivers/net/ethernet/intel/igb/igb_main.c
index 6d812e96572d..69b230c53fed 100644
--- a/drivers/net/ethernet/intel/igb/igb_main.c
+++ b/drivers/net/ethernet/intel/igb/igb_main.c
@@ -1189,15 +1189,15 @@ static int igb_alloc_q_vector(struct igb_adapter *adapter,
 {
 	struct igb_q_vector *q_vector;
 	struct igb_ring *ring;
-	int ring_count, size;
+	int ring_count;
+	size_t size;
 
 	/* igb only supports 1 Tx and/or 1 Rx queue per vector */
 	if (txr_count > 1 || rxr_count > 1)
 		return -ENOMEM;
 
 	ring_count = txr_count + rxr_count;
-	size = sizeof(struct igb_q_vector) +
-	       (sizeof(struct igb_ring) * ring_count);
+	size = struct_size(q_vector, ring, ring_count);
 
 	/* allocate q_vector and rings */
 	q_vector = adapter->q_vector[v_idx];
-- 
2.20.1

Re: [PATCH net-next] igb: use struct_size() helper

[David Miller]

From: "Gustavo A. R. Silva" <gustavo@embeddedor.com>
Date: Thu, 7 Feb 2019 22:15:40 -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 = alloc(size, GFP_KERNEL);
> 
> Instead of leaving these open-coded and prone to type mistakes, we can
> now use the new struct_size() helper:
> 
> size = struct_size(instance, entry, count);
> 
> This code was detected with the help of Coccinelle.
> 
> Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>

Applied.