decnet: dn_rtmsg: Improve input length sanitization in dnrmg_receive_user_skb
authorMateusz Jurczyk <mjurczyk@google.com>
Wed, 7 Jun 2017 14:14:29 +0000 (16:14 +0200)
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Wed, 5 Jul 2017 12:35:12 +0000 (14:35 +0200)
commit80f5fba8d14d799108395d49317c5b57615b6c73
tree4278c2868efa8c94a4b4615d5ef73856a9c67b8e
parent0d487bc50728828ce0f6d817f2c4f8203568c1c8
decnet: dn_rtmsg: Improve input length sanitization in dnrmg_receive_user_skb

[ 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 <mjurczyk@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
net/decnet/netfilter/dn_rtmsg.c