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Subject: Re: [PATCH net-next] svcrdma: Use struct_size() in kmalloc()
From:   Chuck Lever <chuck.lever@oracle.com>
In-Reply-To: <20190115211140.GA16131@embeddedor>
Date:   Tue, 15 Jan 2019 16:49:16 -0500
Cc:     Trond Myklebust <trond.myklebust@hammerspace.com>,
        Anna Schumaker <anna.schumaker@netapp.com>,
        Bruce Fields <bfields@fieldses.org>,
        Jeff Layton <jlayton@kernel.org>,
        "David S. Miller" <davem@davemloft.net>,
        Linux NFS Mailing List <linux-nfs@vger.kernel.org>,
        netdev@vger.kernel.org, linux-kernel@vger.kernel.org
Content-Transfer-Encoding: quoted-printable
Message-Id: <F652FEF1-0FD7-4FFD-80D4-44DBC2FF47B5@oracle.com>
References: <20190115211140.GA16131@embeddedor>
To:     "Gustavo A. R. Silva" <gustavo@embeddedor.com>
Sender: linux-nfs-owner@vger.kernel.org
Precedence: bulk


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:
>=20
> struct foo {
>    int stuff;
>    struct boo entry[];
> };
>=20
> instance =3D kmalloc(sizeof(struct foo) + count * sizeof(struct boo), =
GFP_KERNEL);
>=20
> Instead of leaving these open-coded and prone to type mistakes, we can
> now use the new struct_size() helper:
>=20
> instance =3D kmalloc(struct_size(instance, entry, count), GFP_KERNEL);
>=20
> This code was detected with the help of Coccinelle.
>=20
> 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(-)
>=20
> 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 =3D kmalloc(sizeof(*ctxt) +
> -			       SG_CHUNK_SIZE * sizeof(struct =
scatterlist),
> +		ctxt =3D kmalloc(struct_size(ctxt, rw_first_sgl, =
SG_CHUNK_SIZE),
> 			       GFP_KERNEL);
> 		if (!ctxt)
> 			goto out;
> --=20
> 2.20.1

--
Chuck Lever