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authorMateusz Jurczyk <mjurczyk@google.com>2017-06-07 16:14:29 +0200
committerDavid S. Miller <davem@davemloft.net>2017-06-08 10:51:22 -0400
commitdd0da17b209ed91f39872766634ca967c170ada1 (patch)
tree1d31dd81171bc855f26ac2cfb6f801b7f9889f3c
parentc164772dd32343ee19e276ce0137830557517834 (diff)
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. Signed-off-by: Mateusz Jurczyk <mjurczyk@google.com> Signed-off-by: David S. Miller <davem@davemloft.net>
-rw-r--r--net/decnet/netfilter/dn_rtmsg.c4
1 files changed, 3 insertions, 1 deletions
diff --git a/net/decnet/netfilter/dn_rtmsg.c b/net/decnet/netfilter/dn_rtmsg.c
index 1ed81ac6dd1a..aa8ffecc46a4 100644
--- a/net/decnet/netfilter/dn_rtmsg.c
+++ b/net/decnet/netfilter/dn_rtmsg.c
@@ -102,7 +102,9 @@ 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 (!netlink_capable(skb, CAP_NET_ADMIN))