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 [off-list ref] wrote:

quoted

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 <redacted>

Reviewed-by: Chuck Lever <redacted>

Thank you, Chuck.
--
Gustavo

quoted

---
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