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* [PATCH net-next] xprtrdma: Use struct_size() in kzalloc()
@ 2019-01-31  0:46 Gustavo A. R. Silva
  2019-01-31 14:11 ` Chuck Lever
  0 siblings, 1 reply; 3+ messages in thread
From: Gustavo A. R. Silva @ 2019-01-31  0:46 UTC (permalink / raw)
  To: Trond Myklebust, Anna Schumaker, J. Bruce Fields, Jeff Layton,
	David S. Miller
  Cc: linux-nfs, netdev, linux-kernel, 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[];
};

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

This code was detected with the help of Coccinelle.

Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
---
 net/sunrpc/xprtrdma/verbs.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/net/sunrpc/xprtrdma/verbs.c b/net/sunrpc/xprtrdma/verbs.c
index 4994e75945b8..9e8cf7456840 100644
--- a/net/sunrpc/xprtrdma/verbs.c
+++ b/net/sunrpc/xprtrdma/verbs.c
@@ -811,8 +811,7 @@ static struct rpcrdma_sendctx *rpcrdma_sendctx_create(struct rpcrdma_ia *ia)
 {
 	struct rpcrdma_sendctx *sc;
 
-	sc = kzalloc(sizeof(*sc) +
-		     ia->ri_max_send_sges * sizeof(struct ib_sge),
+	sc = kzalloc(struct_size(sc, sc_sges, ia->ri_max_send_sges),
 		     GFP_KERNEL);
 	if (!sc)
 		return NULL;
-- 
2.20.1


^ permalink raw reply	[flat|nested] 3+ messages in thread

* Re: [PATCH net-next] xprtrdma: Use struct_size() in kzalloc()
  2019-01-31  0:46 [PATCH net-next] xprtrdma: Use struct_size() in kzalloc() Gustavo A. R. Silva
@ 2019-01-31 14:11 ` Chuck Lever
  2019-02-08  3:49   ` Gustavo A. R. Silva
  0 siblings, 1 reply; 3+ messages in thread
From: Chuck Lever @ 2019-01-31 14:11 UTC (permalink / raw)
  To: Gustavo A. R. Silva
  Cc: Trond Myklebust, Anna Schumaker, Bruce Fields, Jeff Layton,
	David S. Miller, Linux NFS Mailing List, netdev, linux-kernel



> On Jan 30, 2019, at 7:46 PM, Gustavo A. R. Silva <gustavo@embeddedor.com> wrote:
> 
> 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[];
> };
> 
> instance = kzalloc(sizeof(struct foo) + count * sizeof(struct boo), 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);
> 
> This code was detected with the help of Coccinelle.
> 
> Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>

Reviewed-by: Chuck Lever <chuck.lever@oracle.com>


> ---
> net/sunrpc/xprtrdma/verbs.c | 3 +--
> 1 file changed, 1 insertion(+), 2 deletions(-)
> 
> diff --git a/net/sunrpc/xprtrdma/verbs.c b/net/sunrpc/xprtrdma/verbs.c
> index 4994e75945b8..9e8cf7456840 100644
> --- a/net/sunrpc/xprtrdma/verbs.c
> +++ b/net/sunrpc/xprtrdma/verbs.c
> @@ -811,8 +811,7 @@ static struct rpcrdma_sendctx *rpcrdma_sendctx_create(struct rpcrdma_ia *ia)
> {
> 	struct rpcrdma_sendctx *sc;
> 
> -	sc = kzalloc(sizeof(*sc) +
> -		     ia->ri_max_send_sges * sizeof(struct ib_sge),
> +	sc = kzalloc(struct_size(sc, sc_sges, ia->ri_max_send_sges),
> 		     GFP_KERNEL);
> 	if (!sc)
> 		return NULL;
> -- 
> 2.20.1
> 

--
Chuck Lever




^ permalink raw reply	[flat|nested] 3+ messages in thread

* Re: [PATCH net-next] xprtrdma: Use struct_size() in kzalloc()
  2019-01-31 14:11 ` Chuck Lever
@ 2019-02-08  3:49   ` Gustavo A. R. Silva
  0 siblings, 0 replies; 3+ messages in thread
From: Gustavo A. R. Silva @ 2019-02-08  3:49 UTC (permalink / raw)
  To: Chuck Lever
  Cc: Trond Myklebust, Anna Schumaker, Bruce Fields, Jeff Layton,
	David S. Miller, Linux NFS Mailing List, netdev, linux-kernel



On 1/31/19 8:11 AM, Chuck Lever wrote:
> 
> 
>> On Jan 30, 2019, at 7:46 PM, Gustavo A. R. Silva <gustavo@embeddedor.com> wrote:
>>
>> 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[];
>> };
>>
>> instance = kzalloc(sizeof(struct foo) + count * sizeof(struct boo), 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);
>>
>> This code was detected with the help of Coccinelle.
>>
>> Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
> 
> Reviewed-by: Chuck Lever <chuck.lever@oracle.com>
> 

Thanks, Chuck.

--
Gustavo

^ permalink raw reply	[flat|nested] 3+ messages in thread

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2019-01-31  0:46 [PATCH net-next] xprtrdma: Use struct_size() in kzalloc() Gustavo A. R. Silva
2019-01-31 14:11 ` Chuck Lever
2019-02-08  3:49   ` Gustavo A. R. Silva

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