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

[Gustavo A. R. Silva]

On 1/15/19 3:49 PM, Chuck Lever wrote:
> On Jan 15, 2019, at 4:11 PM, Gustavo A. R. Silva <gustavo@xxxxxxxxxxxxxx> 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@xxxxxxxxxxxxxx>
>
> Reviewed-by: Chuck Lever <chuck.lever@xxxxxxxxxx>

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