From: yuan linyu <cug...@163.com>
Date: Tue, 3 Jan 2017 20:42:17 +0800
> From: yuan linyu <linyu.y...@alcatel-sbell.com.cn>
>
> sizeof(struct cmsghdr) and sizeof(struct compat_cmsghdr) already aligned.
> remove use CMSG_ALIGN(sizeof(struct cmsghdr)) and
> CMSG_COMPAT_ALIGN(sizeof(struct compat_cmsghdr)) keep code consistent.
>
> Signed-off-by: yuan linyu <linyu.y...@alcatel-sbell.com.cn>
Applied, and I added the following commit which will make sure our
analysis is accurate.
====================
[PATCH] 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 <da...@davemloft.net>
---
net/compat.c | 3 +++
net/socket.c | 2 ++
2 files changed, 5 insertions(+)
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);
diff --git a/net/socket.c b/net/socket.c
index 8487bf1..5f3b5a2 100644
--- a/net/socket.c
+++ b/net/socket.c
@@ -1948,6 +1948,8 @@ static int ___sys_sendmsg(struct socket *sock, struct
user_msghdr __user *msg,
ctl_buf = msg_sys->msg_control;
ctl_len = msg_sys->msg_controllen;
} else if (ctl_len) {
+ BUILD_BUG_ON(sizeof(struct cmsghdr) !=
+ CMSG_ALIGN(sizeof(struct cmsghdr)));
if (ctl_len > sizeof(ctl)) {
ctl_buf = sock_kmalloc(sock->sk, ctl_len, GFP_KERNEL);
if (ctl_buf == NULL)
--
2.4.11
