By using skb_put we ensure that skb->tail is set
correctly. Currently, skb->tail is always zero, which
leads to errors, such as the following page fault in
rfcomm_recv_frame:

    BUG: unable to handle page fault for address: ffffed1021de29ff
    #PF: supervisor read access in kernel mode
    #PF: error_code(0x0000) - not-present page
    RIP: 0010:rfcomm_run+0x831/0x4040 (net/bluetooth/rfcomm/core.c:1751)

Signed-off-by: Soenke Huster <soenke.huster@eknoes.de>
---
 drivers/bluetooth/virtio_bt.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/bluetooth/virtio_bt.c b/drivers/bluetooth/virtio_bt.c
index 67c21263f9e0..fd281d439505 100644
--- a/drivers/bluetooth/virtio_bt.c
+++ b/drivers/bluetooth/virtio_bt.c
@@ -219,7 +219,7 @@ static void virtbt_rx_work(struct work_struct *work)
 	if (!skb)
 		return;
 
-	skb->len = len;
+	skb_put(skb, len);
 	virtbt_rx_handle(vbt, skb);
 
 	if (virtbt_add_inbuf(vbt) < 0)
-- 
2.36.1

Hi Soenke,

On Sun, Jul 24, 2022 at 11:53 PM Soenke Huster <soenke.huster@eknoes.de> wrote:
>
> By using skb_put we ensure that skb->tail is set
> correctly. Currently, skb->tail is always zero, which
> leads to errors, such as the following page fault in
> rfcomm_recv_frame:
>
>     BUG: unable to handle page fault for address: ffffed1021de29ff
>     #PF: supervisor read access in kernel mode
>     #PF: error_code(0x0000) - not-present page
>     RIP: 0010:rfcomm_run+0x831/0x4040 (net/bluetooth/rfcomm/core.c:1751)

Please add the Fixes tag with the original patch that introduced the problem.

> Signed-off-by: Soenke Huster <soenke.huster@eknoes.de>
> ---
>  drivers/bluetooth/virtio_bt.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/bluetooth/virtio_bt.c b/drivers/bluetooth/virtio_bt.c
> index 67c21263f9e0..fd281d439505 100644
> --- a/drivers/bluetooth/virtio_bt.c
> +++ b/drivers/bluetooth/virtio_bt.c
> @@ -219,7 +219,7 @@ static void virtbt_rx_work(struct work_struct *work)
>         if (!skb)
>                 return;
>
> -       skb->len = len;
> +       skb_put(skb, len);
>         virtbt_rx_handle(vbt, skb);
>
>         if (virtbt_add_inbuf(vbt) < 0)
> --
> 2.36.1
>


-- 
Luiz Augusto von Dentz