From 160ed70183207c8beb04668737767f617137d9ac Mon Sep 17 00:00:00 2001 From: Mateusz Jurczyk Date: Wed, 7 Jun 2017 16:14:29 +0200 Subject: [PATCH] decnet: dn_rtmsg: Improve input length sanitization in dnrmg_receive_user_skb Verify that the length of the socket buffer is sufficient to cover the nlmsghdr structure before accessing the nlh->nlmsg_len field for further input sanitization. If the client only supplies 1-3 bytes of data in sk_buff, then nlh->nlmsg_len remains partially uninitialized and contains leftover memory from the corresponding kernel allocation. Operating on such data may result in indeterminate evaluation of the nlmsg_len < sizeof(*nlh) expression. The bug was discovered by a runtime instrumentation designed to detect use of uninitialized memory in the kernel. The patch prevents this and other similar tools (e.g. KMSAN) from flagging this behavior in the future. Change-Id: I75991afbc07f14d6b0518db4e6042ee91e89907c Signed-off-by: Mateusz Jurczyk Signed-off-by: David S. Miller Signed-off-by: Kevin F. Haggerty --- net/decnet/netfilter/dn_rtmsg.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/net/decnet/netfilter/dn_rtmsg.c b/net/decnet/netfilter/dn_rtmsg.c index 1531135130d..db4ae610eeb 100644 --- a/net/decnet/netfilter/dn_rtmsg.c +++ b/net/decnet/netfilter/dn_rtmsg.c @@ -105,7 +105,9 @@ static inline void dnrmg_receive_user_skb(struct sk_buff *skb) { struct nlmsghdr *nlh = nlmsg_hdr(skb); - if (nlh->nlmsg_len < sizeof(*nlh) || skb->len < nlh->nlmsg_len) + if (skb->len < sizeof(*nlh) || + nlh->nlmsg_len < sizeof(*nlh) || + skb->len < nlh->nlmsg_len) return; if (!capable(CAP_NET_ADMIN))