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Re: [PATCH v2] decnet: dn_rtmsg: Improve input length sanitization in dnrmg_receive_user_skb

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Mateusz Jurczyk <mjurczyk@google.com> 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 < 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.

Instead of changing all the internal users wouldn't it be better
to add this check once in netlink_unicast_kernel?

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[PATCH] decnet: dn_rtmsg: Improve input length sanitization in dnrmg_receive_user_skb Mateusz Jurczyk <mjurczyk@google.com> - 2017-06-07 15:20 +0200
  Re: [PATCH v2] decnet: dn_rtmsg: Improve input length sanitization  in dnrmg_receive_user_skb Florian Westphal <fw@strlen.de> - 2017-06-07 16:20 +0200
    Re: [PATCH v2] decnet: dn_rtmsg: Improve input length sanitization in dnrmg_receive_user_skb Mateusz Jurczyk <mjurczyk@google.com> - 2017-06-07 16:50 +0200
      Re: [PATCH v2] decnet: dn_rtmsg: Improve input length sanitization  in dnrmg_receive_user_skb David Miller <davem@davemloft.net> - 2017-06-08 16:40 +0200
  [PATCH v2] decnet: dn_rtmsg: Improve input length sanitization in dnrmg_receive_user_skb Mateusz Jurczyk <mjurczyk@google.com> - 2017-06-07 16:20 +0200

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