netdev - Re: [PATCH iproute2] lib/libnetlink: fix response seq check

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Date:   Wed, 3 Oct 2018 16:01:40 -0700
From:   Vlad Dumitrescu <vlad@...itrescu.ro>
To:     stephen@...workplumber.org, chrism@...lanox.com,
        Mahesh Bandewar <maheshb@...gle.com>
Cc:     netdev@...r.kernel.org, Vlad Dumitrescu <vladum@...gle.com>
Subject: Re: [PATCH iproute2] lib/libnetlink: fix response seq check

Hi,

On Fri, Sep 28, 2018 at 10:14 AM <vlad@...itrescu.ro> wrote:
>
> From: Vlad Dumitrescu <vladum@...gle.com>
>
> Taking a one-iovec example, with rtnl->seq at 42. iovlen == 1, seq
> becomes 43 on line 604, and a message is sent with nlmsg_seq == 43. If
> a response with nlmsg_seq of 42 is received, the condition being fixed
> in this patch would incorrectly accept it.
>
> Fixes: 72a2ff3916e5 ("lib/libnetlink: Add a new function rtnl_talk_iov")
> Signed-off-by: Vlad Dumitrescu <vladum@...gle.com>
> ---
>  lib/libnetlink.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/lib/libnetlink.c b/lib/libnetlink.c
> index f18dceac..4d2416bf 100644
> --- a/lib/libnetlink.c
> +++ b/lib/libnetlink.c
> @@ -647,7 +647,7 @@ static int __rtnl_talk_iov(struct rtnl_handle *rtnl, struct iovec *iov,
>
>                         if (nladdr.nl_pid != 0 ||
>                             h->nlmsg_pid != rtnl->local.nl_pid ||
> -                           h->nlmsg_seq > seq || h->nlmsg_seq < seq - iovlen) {
> +                           h->nlmsg_seq > seq || h->nlmsg_seq < seq - iovlen + 1) {
>                                 /* Don't forget to skip that message. */
>                                 status -= NLMSG_ALIGN(len);
>                                 h = (struct nlmsghdr *)((char *)h + NLMSG_ALIGN(len));
> --
> 2.19.0.605.g01d371f741-goog

Did anybody get a chance to review this? I'm not 100% sure I'm fixing
the right thing.

Thanks,
Vlad