tree 1d31dd81171bc855f26ac2cfb6f801b7f9889f3c
parent c164772dd32343ee19e276ce0137830557517834
author Mateusz Jurczyk <mjurczyk@google.com> 1496844869 +0200
committer David S. Miller <davem@davemloft.net> 1496933482 -0400

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>