netdev - Re: Regression: net/ipv6/mld running system out of memory (not a leak)

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Date:   Thu, 5 Mar 2020 12:02:35 +0800
From:   Hangbin Liu <liuhangbin@...il.com>
To:     Rafał Miłecki <zajec5@...il.com>
Cc:     Network Development <netdev@...r.kernel.org>,
        "David S. Miller" <davem@...emloft.net>,
        Alexey Kuznetsov <kuznet@....inr.ac.ru>,
        Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>,
        Felix Fietkau <nbd@....name>, John Crispin <john@...ozen.org>,
        Jo-Philipp Wich <jo@...n.io>
Subject: Re: Regression: net/ipv6/mld running system out of memory (not a
 leak)

On Wed, Mar 04, 2020 at 11:07:36AM +0100, Rafał Miłecki wrote:
> BINGO.
> 
> Summary:
> Every "ifconfig $dev down" results in:
> ipv6_mc_down() → igmp6_group_dropped() → igmp6_leave_group() → mld_add_delrec()
> & allocating & adding "struct ifmcaddr6" (ff02::2) to the idev->mc_tomb.

Yes, when link down, we store the pmc info in idev->mc_tomb via
mld_add_delrec(), but later when link up, we didn't create new pmc,
but just copy the pmc info in idev->mc_tomb to current idev via
mld_del_delrec() and free the tomb pmc.

> Should I still try it given my above debugging results?

In the new patch, I removed the "ff02::2" address in ipv6_mc_down()
and re-added it in ipv6_mc_up(). I would appreciate if you could help
try it and see if we really did wrong in mld_add_delrec().

Thanks
Hangbin