4.9-stable review patch. If anyone has any objections, please let me know.
------------------ From: Mateusz Jurczyk <[email protected]> [ Upstream commit dd0da17b209ed91f39872766634ca967c170ada1 ] 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 <[email protected]> Signed-off-by: David S. Miller <[email protected]> Signed-off-by: Greg Kroah-Hartman <[email protected]> --- net/decnet/netfilter/dn_rtmsg.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) --- a/net/decnet/netfilter/dn_rtmsg.c +++ b/net/decnet/netfilter/dn_rtmsg.c @@ -102,7 +102,9 @@ static inline void dnrmg_receive_user_sk { 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))
