linux-kernel - Re: [PATCH net] nfc: nci: Fix handling of zero-length payload packets in nci_rx

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Date: Fri, 17 May 2024 00:43:31 +0900 (JST)
From: Shigeru Yoshida <syoshida@...hat.com>
To: ryasuoka@...hat.com
Cc: horms@...nel.org, krzk@...nel.org, davem@...emloft.net,
 edumazet@...gle.com, kuba@...nel.org, pabeni@...hat.com,
 netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH net] nfc: nci: Fix handling of zero-length payload
 packets in nci_rx_work()

Hi Yasuoka-san,

On Thu, 16 May 2024 18:24:54 +0900, Ryosuke Yasuoka wrote:
> Thank you for your review and comment, Simon.
> 
> On Thu, May 16, 2024 at 09:43:48AM +0100, Simon Horman wrote:
>> Hi Yasuoka-san,
>> 
>> On Thu, May 16, 2024 at 12:17:07AM +0900, Ryosuke Yasuoka wrote:
>> > When nci_rx_work() receives a zero-length payload packet, it should
>> > discard the packet without exiting the loop. Instead, it should continue
>> > processing subsequent packets.
>> 
>> nit: I think it would be clearer to say:
>> 
>> ... it should not discard the packet and exit the loop. Instead, ...
> 
> Great. I'll update commit msg like this.
> 
>> > 
>> > Fixes: d24b03535e5e ("nfc: nci: Fix uninit-value in nci_dev_up and nci_ntf_packet")
>> > Closes: https://lore.kernel.org/lkml/20240428134525.GW516117@kernel.org/T/
>> 
>> nit: I'm not sure this Closes link is adding much,
>>      there are more changes coming, right?
> 
> No. I just wanna show the URL link as a reference where this bug is
> found. This URL discuss a little bit different topic as you know.
> 
> In the following discussion [1], Jakub pointed out that changing
> continue statement to break is not related to the patch "Fix
> uninit-value in nci_rw_work". So I posted this new small patch before
> posting v5 patch for "Fix: uninit-value in nci_rw_work".
> 
> If Closes tag is not appropriate, I can remove this in this v2 patch.
> What do you think?

I think this patch, continuing the loop after freeing skb, came from
the following discussion:

https://lore.kernel.org/lkml/Zi-vGH1ROjiv1yJ2@zeus/

In such a case, you can use Link: tag with the above URL and mention
it in the change log like "As discussed [1], ...". But this patch
small and clear, so I think the current change log is enough to convey
the intent of the changes without external link.

You may find the following document helpful:

https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Documentation/process/submitting-patches.rst?h=v6.9#n115

Thanks,
Shigeru

> 
> [1] https://lore.kernel.org/all/20240510190613.72838bf0@kernel.org/
> 
>> > Reported-by: Ryosuke Yasuoka <ryasuoka@...hat.com>
>> > Signed-off-by: Ryosuke Yasuoka <ryasuoka@...hat.com>
>> > ---
>> >  net/nfc/nci/core.c | 3 +--
>> >  1 file changed, 1 insertion(+), 2 deletions(-)
>> > 
>> > diff --git a/net/nfc/nci/core.c b/net/nfc/nci/core.c
>> > index b133dc55304c..f2ae8b0d81b9 100644
>> > --- a/net/nfc/nci/core.c
>> > +++ b/net/nfc/nci/core.c
>> > @@ -1518,8 +1518,7 @@ static void nci_rx_work(struct work_struct *work)
>> >  
>> >  		if (!nci_plen(skb->data)) {
>> >  			kfree_skb(skb);
>> > -			kcov_remote_stop();
>> > -			break;
>> > +			continue;
>> >  		}
>> >  
>> >  		/* Process frame */
>> > -- 
>> > 2.44.0
>> > 
>> > 
>> 
> 
> Thank you for your help.
> Ryosuke
> 
>