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

Krzysztof Kozlowski
2023-11-20T18:44:34Z

On 19/11/2023 17:47, 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@syzkaller.appspotmail.com
> Closes: https://lore.kernel.org/lkml/00000000000075472b06007df4fb@google.com
> Signed-off-by: Nguyen Dinh Phi <phind.uet@gmail.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

As pointed out, drop.

>
> 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);
> -

Drop this change.

> 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) {

Rest looks good, thank you. I think the driver is still not safe for
closing the file descriptor, but that's separate issue.

Please send v2 fixing above points, with a changelog under ---.

Best regards,
Krzysztof