From c73a72f4cbb47672c8cc7f7d7aba52f1cb15baca Mon Sep 17 00:00:00 2001
From: Jakub Kicinski <kuba@kernel.org>
Date: Thu, 17 Nov 2022 19:39:03 -0800
Subject: [PATCH] netlink: remove the flex array from struct nlmsghdr
I've added a flex array to struct nlmsghdr in
commit 738136a0e375 ("netlink: split up copies in the ack construction")
to allow accessing the data easily. It leads to warnings with clang,
if user space wraps this structure into another struct and the flex
array is not at the end of the container.
Reviewed-by: Kees Cook <keescook@chromium.org>
Reviewed-by: David Ahern <dsahern@kernel.org>
Link: https://lore.kernel.org/all/20221114023927.GA685@u2004-local/
Link: https://lore.kernel.org/r/20221118033903.1651026-1-kuba@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
---
include/uapi/linux/netlink.h | 2 --
net/netlink/af_netlink.c | 2 +-
2 files changed, 1 insertion(+), 3 deletions(-)
diff --git a/include/uapi/linux/netlink.h b/include/uapi/linux/netlink.h
index 5da0da59bf01..e2ae82e3f9f7 100644
--- a/include/uapi/linux/netlink.h
+++ b/include/uapi/linux/netlink.h
@@ -48,7 +48,6 @@ struct sockaddr_nl {
* @nlmsg_flags: Additional flags
* @nlmsg_seq: Sequence number
* @nlmsg_pid: Sending process port ID
- * @nlmsg_data: Message payload
*/
struct nlmsghdr {
__u32 nlmsg_len;
@@ -56,7 +55,6 @@ struct nlmsghdr {
__u16 nlmsg_flags;
__u32 nlmsg_seq;
__u32 nlmsg_pid;
- __u8 nlmsg_data[];
};
/* Flags values */
diff --git a/net/netlink/af_netlink.c b/net/netlink/af_netlink.c
index 9ebdf3262015..d73091f6bb0f 100644
--- a/net/netlink/af_netlink.c
+++ b/net/netlink/af_netlink.c
@@ -2514,7 +2514,7 @@ void netlink_ack(struct sk_buff *in_skb, struct nlmsghdr *nlh, int err,
if (!nlmsg_append(skb, nlmsg_len(nlh)))
goto err_bad_put;
- memcpy(errmsg->msg.nlmsg_data, nlh->nlmsg_data,
+ memcpy(nlmsg_data(&errmsg->msg), nlmsg_data(nlh),
nlmsg_len(nlh));
}
--
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