Re: [PATCH v2] netfilter: nfnetlink: Improve input length sanitization in nfnetlink_rcv

[Pablo Neira Ayuso]

On Wed, Jun 07, 2017 at 03:50:38PM +0200, Mateusz Jurczyk wrote:
> 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 < NLMSG_HDRLEN 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.

Applied, thanks.