[PATCH 62/64] netlink: Avoid false-positive memcpy() warning
From: Kees Cook <hidden>
Date: 2021-07-27 21:19:23
Also in:
dri-devel, linux-hardening, linux-kbuild, linux-staging, linux-wireless, lkml, netdev
Subsystem:
networking [general], the rest · Maintainers:
"David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, Linus Torvalds
In preparation for FORTIFY_SOURCE performing compile-time and run-time field bounds checking for memcpy(), memmove(), and memset(), avoid intentionally writing across neighboring fields. Add a flexible array member to mark the end of struct nlmsghdr, and split the memcpy() to avoid false positive memcpy() warning: memcpy: detected field-spanning write (size 32) of single field (size 16) Signed-off-by: Kees Cook <redacted> --- include/uapi/linux/netlink.h | 1 + net/netlink/af_netlink.c | 4 +++- 2 files changed, 4 insertions(+), 1 deletion(-)
diff --git a/include/uapi/linux/netlink.h b/include/uapi/linux/netlink.h
index 4c0cde075c27..ddeaa748df5e 100644
--- a/include/uapi/linux/netlink.h
+++ b/include/uapi/linux/netlink.h@@ -47,6 +47,7 @@ struct nlmsghdr { __u16 nlmsg_flags; /* Additional flags */ __u32 nlmsg_seq; /* Sequence number */ __u32 nlmsg_pid; /* Sending process port ID */ + __u8 contents[]; }; /* Flags values */
diff --git a/net/netlink/af_netlink.c b/net/netlink/af_netlink.c
index 24b7cf447bc5..f2dd99e96822 100644
--- a/net/netlink/af_netlink.c
+++ b/net/netlink/af_netlink.c@@ -2447,7 +2447,9 @@ void netlink_ack(struct sk_buff *in_skb, struct nlmsghdr *nlh, int err, NLMSG_ERROR, payload, flags); errmsg = nlmsg_data(rep); errmsg->error = err; - memcpy(&errmsg->msg, nlh, payload > sizeof(*errmsg) ? nlh->nlmsg_len : sizeof(*nlh)); + memcpy(&errmsg->msg, nlh, sizeof(*nlh)); + if (payload > sizeof(*errmsg)) + memcpy(errmsg->msg.contents, nlh->contents, nlh->nlmsg_len - sizeof(*nlh)); if (nlk_has_extack && extack) { if (extack->_msg) {
--
2.30.2