net: Assert at build time the assumptions we make about the CMSG header.
It must always be the case that CMSG_ALIGN(sizeof(hdr)) == sizeof(hdr).
Otherwise there are missing adjustments in the various calculations
that parse and build these things.
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/compat.c b/net/compat.c
index 4e27dd1..ba3ac72 100644
--- a/net/compat.c
+++ b/net/compat.c
@@ -130,6 +130,9 @@ int cmsghdr_from_user_compat_to_kern(struct msghdr *kmsg, struct sock *sk,
__kernel_size_t kcmlen, tmp;
int err = -EFAULT;
+ BUILD_BUG_ON(sizeof(struct compat_cmsghdr) !=
+ CMSG_COMPAT_ALIGN(sizeof(struct compat_cmsghdr)));
+
kcmlen = 0;
kcmsg_base = kcmsg = (struct cmsghdr *)stackbuf;
ucmsg = CMSG_COMPAT_FIRSTHDR(kmsg);
