netdev - Re: [PATCH net] mld: fix panic in mld

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Message-ID: <CAMArcTWCY49YxbVnYjWxH=e+J+oFVjXQ1cJKxLorULXYw-c=+Q@mail.gmail.com>
Date:   Sun, 27 Dec 2020 23:40:11 +0900
From:   Taehee Yoo <ap420073@...il.com>
To:     Cong Wang <xiyou.wangcong@...il.com>
Cc:     David Miller <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Linux Kernel Network Developers <netdev@...r.kernel.org>,
        Eric Dumazet <eric.dumazet@...il.com>
Subject: Re: [PATCH net] mld: fix panic in mld_newpack()

On Sun, 27 Dec 2020 at 04:27, Cong Wang <xiyou.wangcong@...il.com> wrote:
>

Hi Cong,
Thank you so much for the review!

> On Wed, Dec 23, 2020 at 8:55 AM Taehee Yoo <ap420073@...il.com> wrote:
> >
> > mld_newpack() doesn't allow to allocate high order page,
> > just order-0 allocation is allowed.
> > If headroom size is too large, a kernel panic could occur in skb_put().
> ...
> > Allowing high order page allocation could fix this problem.
> >
> > Fixes: 72e09ad107e7 ("ipv6: avoid high order allocations")
>
> So you just revert this commit which fixes another issue. ;)
>

Yes, This patch is actually to revert 72e09ad107e7 commit.
But I found conflict while I do "git revert". so I just sent a normal patch :)

> How about changing timers to delayed works so that we can
> make both sides happy? It is certainly much more work, but
> looks worthy of it.
>

Thank you so much for your advice!
But I'm so sorry I didn't understand some points.

1. you said "both side" and I understand these as follows:
a) failure of allocation because of a high order and it is fixed
by 72e09ad107e7
b) kernel panic because of 72e09ad107e7
Are these two issues right?

2. So, as far as I understand your mention, these timers are
good to be changed to the delayed works And these timers are mca_timer,
mc_gq_timer, mc_ifc_timer, mc_dad_timer.
Do I understand your mention correctly?
If so, what is the benefit of it?
I, unfortunately, couldn't understand the relationship between changing
timers to the delayed works and these issues.

Could you please explain the above things again?

Thank you!