netdev - Re: [PATCH net 2/3] bpf, mlx5: fix various refcount/prog issues in mlx5e_xdp

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Message-ID: <582A0124.2040100@iogearbox.net>
Date:   Mon, 14 Nov 2016 19:23:32 +0100
From:   Daniel Borkmann <daniel@...earbox.net>
To:     Alexei Starovoitov <alexei.starovoitov@...il.com>
CC:     davem@...emloft.net, bblanco@...mgrid.com, tariqt@...lanox.com,
        zhiyisun@...il.com, ranas@...lanox.com, netdev@...r.kernel.org
Subject: Re: [PATCH net 2/3] bpf, mlx5: fix various refcount/prog issues in
 mlx5e_xdp_set

On 11/14/2016 06:35 PM, Alexei Starovoitov wrote:
> On Mon, Nov 14, 2016 at 09:49:49AM +0100, Daniel Borkmann wrote:
>> On 11/14/2016 03:49 AM, Alexei Starovoitov wrote:
>>> On Mon, Nov 14, 2016 at 01:43:41AM +0100, Daniel Borkmann wrote:
>> [...]
>>>> diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
>>>> index 751e806..a0fca9f 100644
>>>> --- a/kernel/bpf/syscall.c
>>>> +++ b/kernel/bpf/syscall.c
>>>> @@ -682,6 +682,17 @@ struct bpf_prog *bpf_prog_add(struct bpf_prog *prog, int i)
>>>>   }
>>>>   EXPORT_SYMBOL_GPL(bpf_prog_add);
>>>>
>>>> +void bpf_prog_sub(struct bpf_prog *prog, int i)
>>>> +{
>>>> +	/* Only to be used for undoing previous bpf_prog_add() in some
>>>> +	 * error path. We still know that another entity in our call
>>>> +	 * path holds a reference to the program, thus atomic_sub() can
>>>> +	 * be safely used in such cases!
>>>> +	 */
>>>> +	WARN_ON(atomic_sub_return(i, &prog->aux->refcnt) == 0);
>>>> +}
>>>> +EXPORT_SYMBOL_GPL(bpf_prog_sub);
>>>
>>> the patches look good. I'm only worried about net/net-next merge
>>> conflict here. (I would have to deal with it as well).
>>> So instead of copying the above helper can we apply net-next's
>>> 'bpf, mlx4: fix prog refcount in mlx4_en_try_alloc_resources error path'
>>> patch to net without mlx4_xdp_set hunk and then apply
>>> the rest of this patch?
>>> Even better is to send this patch 2/3 to net-next?
>>> yes, it's an issue, but very small one. There is no security
>>> concern here, so I would prefer to avoid merge conflict.
>>> Did you do a test merge of net/net-next by any chance?
>>
>> Yes, I did a test merge and git resolved the above just fine w/o
>> any conflicts. I have no strong opinion whether net or net-next.
>> If preferred, I can just resend this series in the evening against
>> net-next instead, perhaps that's a bit better.
>
> I have slight preference to go via net-next, but since it merges fine,
> I don't mind net route too.

Ok, I'll rebase for net-next then.