netdev - Re: [PATCH v2] ipv6: acquire write lock for addr_list in dev_forward

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Date:   Mon, 21 Mar 2022 09:42:14 -0600
From:   David Ahern <dsahern@...nel.org>
To:     Niels Dossche <dossche.niels@...il.com>,
        Paolo Abeni <pabeni@...hat.com>, netdev@...r.kernel.org
Cc:     "David S. Miller" <davem@...emloft.net>,
        Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>,
        Jakub Kicinski <kuba@...nel.org>
Subject: Re: [PATCH v2] ipv6: acquire write lock for addr_list in
 dev_forward_change

On 3/19/22 7:17 AM, Niels Dossche wrote:
> I have an additional question about the locks on the addr_list actually.
> In addrconf_ifdown, there's a loop on addr_list within a write lock in idev->lock
>> list_for_each_entry_safe(ifa, tmp, &idev->addr_list, if_list)
> The loop body unlocks the idev->lock and reacquires it later. I assume because of the lock dependency on ifa->lock and the calls that acquire the mc_lock? Shouldn't that list iteration also be protected during the whole iteration?
> 


That loop needs to be improved as well. Locking in ipv6 code is a bit
hairy.