linux-kernel - Re: [net RFC v1 1/1] page_pool: fix NULL dereference crash

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Date:   Sat, 22 Jan 2022 09:31:17 +0100
From:   Jesper Dangaard Brouer <jbrouer@...hat.com>
To:     Colin Foster <colin.foster@...advantage.com>,
        Alexei Starovoitov <alexei.starovoitov@...il.com>
Cc:     brouer@...hat.com, LKML <linux-kernel@...r.kernel.org>,
        Network Development <netdev@...r.kernel.org>,
        Toke Høiland-Jørgensen <toke@...hat.com>,
        John Fastabend <john.fastabend@...il.com>,
        Alexei Starovoitov <ast@...nel.org>,
        Jakub Kicinski <kuba@...nel.org>,
        "David S. Miller" <davem@...emloft.net>,
        Ilias Apalodimas <ilias.apalodimas@...aro.org>,
        Jesper Dangaard Brouer <hawk@...nel.org>
Subject: Re: [net RFC v1 1/1] page_pool: fix NULL dereference crash



On 22/01/2022 03.40, Colin Foster wrote:
> On Fri, Jan 21, 2022 at 05:13:28PM -0800, Alexei Starovoitov wrote:
>> On Fri, Jan 21, 2022 at 4:57 PM Colin Foster
>> <colin.foster@...advantage.com> wrote:
>>>
>>> Check for the existence of page pool params before dereferencing. This can
>>> cause crashes in certain conditions.
>>
>> In what conditions?
>> Out of tree driver?
>>
>>> Fixes: 35b2e549894b ("page_pool: Add callback to init pages when they are
>>> allocated")
>>>
>>> Signed-off-by: Colin Foster <colin.foster@...advantage.com>
>>> ---
>>>   net/core/page_pool.c | 2 +-
>>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>>
>>> diff --git a/net/core/page_pool.c b/net/core/page_pool.c
>>> index bd62c01a2ec3..641f849c95e7 100644
>>> --- a/net/core/page_pool.c
>>> +++ b/net/core/page_pool.c
>>> @@ -213,7 +213,7 @@ static void page_pool_set_pp_info(struct page_pool *pool,
>>>   {
>>>          page->pp = pool;
>>>          page->pp_magic |= PP_SIGNATURE;
>>> -       if (pool->p.init_callback)
>>> +       if (pool->p && pool->p.init_callback)
> 
> And my apologies - this should be if (pool... not if (pool->p. kernelbot
> will be sure to tell me of this blunder soon

Can you confirm if your crash is fixed by this change?


>>>                  pool->p.init_callback(page, pool->p.init_arg);
>>>   }