netdev - Re: [PATCH net-next] ipv6: do not check fib6_has_expires() in fib6_info

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Date: Thu, 7 Dec 2023 12:27:39 -0800
From: Kui-Feng Lee <sinquersw@...il.com>
To: David Ahern <dsahern@...nel.org>, Eric Dumazet <edumazet@...gle.com>,
 "David S . Miller" <davem@...emloft.net>, Jakub Kicinski <kuba@...nel.org>,
 Paolo Abeni <pabeni@...hat.com>
Cc: netdev@...r.kernel.org, eric.dumazet@...il.com,
 syzbot+c15aa445274af8674f41@...kaller.appspotmail.com,
 Kui-Feng Lee <thinker.li@...il.com>
Subject: Re: [PATCH net-next] ipv6: do not check fib6_has_expires() in
 fib6_info_release()



On 12/7/23 12:25, David Ahern wrote:
> On 12/7/23 1:13 PM, Eric Dumazet wrote:
>> My prior patch went a bit too far, because apparently fib6_has_expires()
>> could be true while f6i->gc_link is not hashed yet.
> 
> yes, and I got distracted by that stack trace and avoiding errors in the
> create function. The diff I sent does not solve any corruption with list
> since the newly allocated f6i is not linked (and gc-link is initialized).
> 
> Kui-Feng: no need to send that patch again since it is not really
> changing anything. Let's see if the other warn on triggers.

Got it!

> 
>>
>> fib6_set_expires_locked() can indeed set RTF_EXPIRES
>> while f6i->fib6_table is NULL.
>>
>> Original syzbot reports were about corruptions caused
>> by dangling f6i->gc_link.
>>
>> Fixes: 5a08d0065a91 ("ipv6: add debug checks in fib6_info_release()")
>> Reported-by: syzbot+c15aa445274af8674f41@...kaller.appspotmail.com
>> Signed-off-by: Eric Dumazet <edumazet@...gle.com>
>> Cc: David Ahern <dsahern@...nel.org>
>> Cc: Kui-Feng Lee <thinker.li@...il.com>
>> ---
>>   include/net/ip6_fib.h | 1 -
>>   1 file changed, 1 deletion(-)
>>
> 
> 
> Reviewed-by: David Ahern <dsahern@...nel.org>
> 
>