2019-01-16 12:52:52

by Gustavo A. R. Silva

Subject: [PATCH net-next] svcrdma: Use struct_size() in kmalloc()

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 <[email protected]>
---
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

2019-01-16 14:20:58

by Chuck Lever III

Subject: Re: [PATCH net-next] svcrdma: Use struct_size() in kmalloc()

On Jan 15, 2019, at 4:11 PM, Gustavo A. R. Silva <[email protected]> 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 <[email protected]>

Reviewed-by: Chuck Lever <[email protected]>


> ---
> 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

2019-01-16 15:08:21

by Gustavo A. R. Silva

Subject: Re: [PATCH net-next] svcrdma: Use struct_size() in kmalloc()

On 1/15/19 3:49 PM, Chuck Lever wrote:
>
>
> On Jan 15, 2019, at 4:11 PM, Gustavo A. R. Silva <[email protected]> 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 <[email protected]>
>
> Reviewed-by: Chuck Lever <[email protected]>
>

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
>
>
>

2019-01-17 01:00:19

by J. Bruce Fields

Subject: Re: [PATCH net-next] svcrdma: Use struct_size() in kmalloc()

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 <[email protected]> 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 <[email protected]>
>
> Reviewed-by: Chuck Lever <[email protected]>

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
>
>