[net-next] svcrdma: Use struct_size() in kmalloc()
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Message ID 20190115211140.GA16131@embeddedor
State New
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Series
  • [net-next] svcrdma: Use struct_size() in kmalloc()
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Commit Message

Gustavo A. R. Silva Jan. 15, 2019, 9:11 p.m. UTC
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 = kmalloc(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 = kmalloc(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/svc_rdma_rw.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

Comments

Chuck Lever Jan. 15, 2019, 9:49 p.m. UTC | #1
On Jan 15, 2019, at 4:11 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 = kmalloc(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 = kmalloc(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/svc_rdma_rw.c | 3 +--
> 1 file changed, 1 insertion(+), 2 deletions(-)
> 
> diff --git a/net/sunrpc/xprtrdma/svc_rdma_rw.c b/net/sunrpc/xprtrdma/svc_rdma_rw.c
> index dc1951759a8e..cad37c2122ab 100644
> --- a/net/sunrpc/xprtrdma/svc_rdma_rw.c
> +++ b/net/sunrpc/xprtrdma/svc_rdma_rw.c
> @@ -64,8 +64,7 @@ svc_rdma_get_rw_ctxt(struct svcxprt_rdma *rdma, unsigned int sges)
> 		spin_unlock(&rdma->sc_rw_ctxt_lock);
> 	} else {
> 		spin_unlock(&rdma->sc_rw_ctxt_lock);
> -		ctxt = kmalloc(sizeof(*ctxt) +
> -			       SG_CHUNK_SIZE * sizeof(struct scatterlist),
> +		ctxt = kmalloc(struct_size(ctxt, rw_first_sgl, SG_CHUNK_SIZE),
> 			       GFP_KERNEL);
> 		if (!ctxt)
> 			goto out;
> -- 
> 2.20.1

--
Chuck Lever
Gustavo A. R. Silva Jan. 15, 2019, 9:53 p.m. UTC | #2
On 1/15/19 3:49 PM, Chuck Lever wrote:
> 
> 
> On Jan 15, 2019, at 4:11 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 = kmalloc(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 = kmalloc(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>
> 

Thank you, Chuck.
--
Gustavo

> 
>> ---
>> net/sunrpc/xprtrdma/svc_rdma_rw.c | 3 +--
>> 1 file changed, 1 insertion(+), 2 deletions(-)
>>
>> diff --git a/net/sunrpc/xprtrdma/svc_rdma_rw.c b/net/sunrpc/xprtrdma/svc_rdma_rw.c
>> index dc1951759a8e..cad37c2122ab 100644
>> --- a/net/sunrpc/xprtrdma/svc_rdma_rw.c
>> +++ b/net/sunrpc/xprtrdma/svc_rdma_rw.c
>> @@ -64,8 +64,7 @@ svc_rdma_get_rw_ctxt(struct svcxprt_rdma *rdma, unsigned int sges)
>> 		spin_unlock(&rdma->sc_rw_ctxt_lock);
>> 	} else {
>> 		spin_unlock(&rdma->sc_rw_ctxt_lock);
>> -		ctxt = kmalloc(sizeof(*ctxt) +
>> -			       SG_CHUNK_SIZE * sizeof(struct scatterlist),
>> +		ctxt = kmalloc(struct_size(ctxt, rw_first_sgl, SG_CHUNK_SIZE),
>> 			       GFP_KERNEL);
>> 		if (!ctxt)
>> 			goto out;
>> -- 
>> 2.20.1
> 
> --
> Chuck Lever
> 
> 
>
J. Bruce Fields Jan. 16, 2019, 11:07 p.m. UTC | #3
On Tue, Jan 15, 2019 at 04:49:16PM -0500, Chuck Lever wrote:
> 
> 
> On Jan 15, 2019, at 4:11 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 = kmalloc(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 = kmalloc(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, applying for 5.1.--b.

> 
> 
> > ---
> > net/sunrpc/xprtrdma/svc_rdma_rw.c | 3 +--
> > 1 file changed, 1 insertion(+), 2 deletions(-)
> > 
> > diff --git a/net/sunrpc/xprtrdma/svc_rdma_rw.c b/net/sunrpc/xprtrdma/svc_rdma_rw.c
> > index dc1951759a8e..cad37c2122ab 100644
> > --- a/net/sunrpc/xprtrdma/svc_rdma_rw.c
> > +++ b/net/sunrpc/xprtrdma/svc_rdma_rw.c
> > @@ -64,8 +64,7 @@ svc_rdma_get_rw_ctxt(struct svcxprt_rdma *rdma, unsigned int sges)
> > 		spin_unlock(&rdma->sc_rw_ctxt_lock);
> > 	} else {
> > 		spin_unlock(&rdma->sc_rw_ctxt_lock);
> > -		ctxt = kmalloc(sizeof(*ctxt) +
> > -			       SG_CHUNK_SIZE * sizeof(struct scatterlist),
> > +		ctxt = kmalloc(struct_size(ctxt, rw_first_sgl, SG_CHUNK_SIZE),
> > 			       GFP_KERNEL);
> > 		if (!ctxt)
> > 			goto out;
> > -- 
> > 2.20.1
> 
> --
> Chuck Lever
> 
>

Patch
diff mbox series

diff --git a/net/sunrpc/xprtrdma/svc_rdma_rw.c b/net/sunrpc/xprtrdma/svc_rdma_rw.c
index dc1951759a8e..cad37c2122ab 100644
--- a/net/sunrpc/xprtrdma/svc_rdma_rw.c
+++ b/net/sunrpc/xprtrdma/svc_rdma_rw.c
@@ -64,8 +64,7 @@  svc_rdma_get_rw_ctxt(struct svcxprt_rdma *rdma, unsigned int sges)
 		spin_unlock(&rdma->sc_rw_ctxt_lock);
 	} else {
 		spin_unlock(&rdma->sc_rw_ctxt_lock);
-		ctxt = kmalloc(sizeof(*ctxt) +
-			       SG_CHUNK_SIZE * sizeof(struct scatterlist),
+		ctxt = kmalloc(struct_size(ctxt, rw_first_sgl, SG_CHUNK_SIZE),
 			       GFP_KERNEL);
 		if (!ctxt)
 			goto out;