bpf: Use struct_size() in kzalloc()

Make use of the struct_size() helper instead of an open-coded version,
in order to avoid any potential type mistakes or integer overflows
that, in the worst scenario, could lead to heap overflows.

This code was detected with the help of Coccinelle and, audited and
fixed manually.

Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/core/bpf_sk_storage.c b/net/core/bpf_sk_storage.c
index cc3712ad8716feb2744dc171a04fd415f905f375..f564f82e91d9ac894d60ab51e0a2d82687d155f1 100644 (file)
--- a/net/core/bpf_sk_storage.c
+++ b/net/core/bpf_sk_storage.c
@@ -524,8 +524,7 @@ bpf_sk_storage_diag_alloc(const struct nlattr *nla_stgs)
                        nr_maps++;
        }
 
-       diag = kzalloc(sizeof(*diag) + sizeof(diag->maps[0]) * nr_maps,
-                      GFP_KERNEL);
+       diag = kzalloc(struct_size(diag, maps, nr_maps), GFP_KERNEL);
        if (!diag)
                return ERR_PTR(-ENOMEM);