linux-kernel - Re: [PATCH] usbip: Fix free of unallocated memory in vhci tx

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Date:   Mon, 21 Oct 2019 17:08:05 +0200 (CEST)
From:   Julia Lawall <julia.lawall@...6.fr>
To:     Suwan Kim <suwan.kim027@...il.com>
cc:     shuah@...nel.org, gregkh@...uxfoundation.org,
        linux-kernel@...r.kernel.org, linux-usb@...r.kernel.org,
        julia.lawall@...6.fr, valentina.manea.m@...il.com,
        kbuild test robot <lkp@...el.com>
Subject: Re: [PATCH] usbip: Fix free of unallocated memory in vhci tx



On Mon, 21 Oct 2019, Suwan Kim wrote:

> iso_buffer should be set to NULL after use and free in the while loop.
> In the case of isochronous URB in the while loop, iso_buffer is
> allocated and after sending it to server, buffer is deallocated. And
> then, if the next URB in the while loop is not a isochronous pipe,
> iso_buffer still holds the previously deallocated buffer address and
> kfree tries to free wrong buffer address.
>
> Fixes: ea44d190764b (“usbip: Implement SG support to vhci-hcd and stub driver”)
> Reported-by: kbuild test robot <lkp@...el.com>
> Reported-by: Julia Lawall <julia.lawall@...6.fr>
> Signed-off-by: Suwan Kim <suwan.kim027@...il.com>
> ---
>  drivers/usb/usbip/vhci_tx.c | 1 +
>  1 file changed, 1 insertion(+)
>
> diff --git a/drivers/usb/usbip/vhci_tx.c b/drivers/usb/usbip/vhci_tx.c
> index c3803785f6ef..b290e810d11b 100644
> --- a/drivers/usb/usbip/vhci_tx.c
> +++ b/drivers/usb/usbip/vhci_tx.c
> @@ -73,6 +73,7 @@ static int vhci_send_cmd_submit(struct vhci_device *vdev)
>  		memset(&pdu_header, 0, sizeof(pdu_header));
>  		memset(&msg, 0, sizeof(msg));
>  		memset(&iov, 0, sizeof(iov));
> +		iso_buffer = NULL;

Somehow I would have put it after the kfree, since the kfree makes the
value invalid.  iso_buffer is already initialized to NULL for the first
iteration.  If you want to put the setting to NULL at the top of the loop,
maybe the = NULL in the first line should be removed.

julia

>
>  		usbip_dbg_vhci_tx("setup txdata urb seqnum %lu\n",
>  				  priv->seqnum);
> --
> 2.21.0
>
>