From: Simon Horman <horms@kernel.org>
To: Ryosuke Yasuoka <ryasuoka@redhat.com>
Cc: krzk@kernel.org, davem@davemloft.net, edumazet@google.com,
kuba@kernel.org, pabeni@redhat.com, netdev@vger.kernel.org,
linux-kernel@vger.kernel.org, syoshida@redhat.com,
syzbot+d7b4dc6cd50410152534@syzkaller.appspotmail.com
Subject: Re: [PATCH net v2] nfc: nci: Fix uninit-value in nci_rx_work
Date: Mon, 29 Apr 2024 17:41:18 +0100 [thread overview]
Message-ID: <20240429164118.GB516117@kernel.org> (raw)
In-Reply-To: <Zi-vGH1ROjiv1yJ2@zeus>
On Mon, Apr 29, 2024 at 11:30:48PM +0900, Ryosuke Yasuoka wrote:
> On Sun, Apr 28, 2024 at 02:45:25PM +0100, Simon Horman wrote:
> > On Sat, Apr 27, 2024 at 07:35:54PM +0900, Ryosuke Yasuoka wrote:
...
> Thank you for your comment, Simon.
>
> Yes, if it handles packets correctly in nci_{rsp,ntf,rx_data}_packet(),
> it should not reach invalid_pkt_free and it should continue to work in
> the for statement. Sorry, it is my mistake and need to fix it.
>
> BTW, in the current implementation, if the payload is zero, it will free
> the skb and exit the for statement. I wonder it is intended.
>
> > > - if (!nci_plen(skb->data)) {
> > > - kfree_skb(skb);
> > > - break;
> > > - }
>
> When the packet is invalid, it should be discarded but it should not
> exit the for statement by break. Instead, the skb should just free and
> it should handle the subsequent packet by continue. If yes, then it
> may be like below,
>
> for (; (skb = skb_dequeue(&ndev->rx_q)); kcov_remote_stop()) {
> kcov_remote_start_common(skb_get_kcov_handle(skb));
>
> /* Send copy to sniffer */
> nfc_send_to_raw_sock(ndev->nfc_dev, skb,
> RAW_PAYLOAD_NCI, NFC_DIRECTION_RX);
>
> if (!skb->len)
> goto invalid_pkt_free;
>
> /* Process frame */
> switch (nci_mt(skb->data)) {
> case NCI_MT_RSP_PKT:
> if (!nci_valid_size(skb, NCI_CTRL_HDR_SIZE))
> goto invalid_pkt_free;
> nci_rsp_packet(ndev, skb);
> continue; <<<---
>
> case NCI_MT_NTF_PKT:
> if (!nci_valid_size(skb, NCI_CTRL_HDR_SIZE))
> goto invalid_pkt_free;
> nci_ntf_packet(ndev, skb);
> continue; <<<---
>
> case NCI_MT_DATA_PKT:
> if (!nci_valid_size(skb, NCI_DATA_HDR_SIZE))
> goto invalid_pkt_free;
> nci_rx_data_packet(ndev, skb);
> continue; <<<---
>
> default:
> pr_err("unknown MT 0x%x\n", nci_mt(skb->data));
> goto invalid_pkt_free;
> }
> invalid_pkt_free:
> kfree_skb(skb);
> }
>
> Could I hear your opinion?
Hi Yasuoka-san,
Thanks for pointing this out.
I agree that it is not good to 'break' after kfree_skb() for two reasons:
1. As you mention, the loop should keep going and process other skbs
2. kcov_remote_stop() needs to be called for each skb
I might have used a 'continue' above the invalid_pkt_free label.
But I think your suggestion - using 'continue' inside the switch statement
- is also correct, and seems fine to me.
Please post a v3 when you are ready.
--
pw-bot: changes-requested
prev parent reply other threads:[~2024-04-29 16:41 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-04-27 10:35 [PATCH net v2] nfc: nci: Fix uninit-value in nci_rx_work Ryosuke Yasuoka
2024-04-28 13:45 ` Simon Horman
2024-04-29 14:30 ` Ryosuke Yasuoka
2024-04-29 16:41 ` Simon Horman [this message]
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