linux-kernel - Re: [PATCH] nfc: virtual_ncidev: Add variable to check if ndev is running

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Message-ID: <20231120044706epcms2p48c4579db14cc4f3274031036caac4718@epcms2p4>
Date:   Mon, 20 Nov 2023 13:47:06 +0900
From:   Bongsu Jeon <bongsu.jeon@...sung.com>
To:     Nguyen Dinh Phi <phind.uet@...il.com>,
        Bongsu Jeon <bongsu.jeon@...sung.com>,
        "krzysztof.kozlowski@...aro.org" <krzysztof.kozlowski@...aro.org>
CC:     "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "syzbot+6eb09d75211863f15e3e@...kaller.appspotmail.com" 
        <syzbot+6eb09d75211863f15e3e@...kaller.appspotmail.com>
Subject: Re: [PATCH] nfc: virtual_ncidev: Add variable to check if ndev is
 running


On 20/11/2023 01:47, Nguyen Dinh Phi wrote:

> syzbot reported an memory leak that happens when an skb is add to
> send_buff after virtual nci closed.
> This patch adds a variable to track if the ndev is running before
> handling new skb in send function.
> 
> Reported-by: syzbot+6eb09d75211863f15e3e@...kaller.appspotmail.com
> Closes: https://lore.kernel.org/lkml/00000000000075472b06007df4fb@google.com
> Signed-off-by: Nguyen Dinh Phi <phind.uet@...il.com>
> ---
>  drivers/nfc/virtual_ncidev.c | 9 +++++++--
>  1 file changed, 7 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/nfc/virtual_ncidev.c b/drivers/nfc/virtual_ncidev.c
> index b027be0b0b6f..ac8226db54e2 100644
> --- a/drivers/nfc/virtual_ncidev.c
> +++ b/drivers/nfc/virtual_ncidev.c
> @@ -20,26 +20,31 @@
>                                   NFC_PROTO_ISO14443_MASK | \
>                                   NFC_PROTO_ISO14443_B_MASK | \
>                                   NFC_PROTO_ISO15693_MASK)
> +#define NCIDEV_RUNNING 0
This define isn't used.

>  
>  struct virtual_nci_dev {
>          struct nci_dev *ndev;
>          struct mutex mtx;
>          struct sk_buff *send_buff;
>          struct wait_queue_head wq;
> +        bool running;
>  };
>  
>  static int virtual_nci_open(struct nci_dev *ndev)
>  {
> +        struct virtual_nci_dev *vdev = nci_get_drvdata(ndev);
> +
> +        vdev->running = true;
>          return 0;
>  }
>  
>  static int virtual_nci_close(struct nci_dev *ndev)
>  {
>          struct virtual_nci_dev *vdev = nci_get_drvdata(ndev);
> -
>          mutex_lock(&vdev->mtx);
>          kfree_skb(vdev->send_buff);
>          vdev->send_buff = NULL;
> +        vdev->running = false;
>          mutex_unlock(&vdev->mtx);
>  
>          return 0;
> @@ -50,7 +55,7 @@ static int virtual_nci_send(struct nci_dev *ndev, struct sk_buff *skb)
>          struct virtual_nci_dev *vdev = nci_get_drvdata(ndev);
>  
>          mutex_lock(&vdev->mtx);
> -        if (vdev->send_buff) {
> +        if (vdev->send_buff || !vdev->running) {

Dear Krzysztof,

I agree this defensive code.
But i think NFC submodule has to avoid this situation.(calling send function of closed nci_dev)
Could you check this?

Best regards,
Bongsu