Re: [PATCH V2] usb: musb: Get the musb_qh poniter after musb_giveback

[Greg KH <gregkh@linuxfoundation.org>]

On Mon, Sep 18, 2023 at 02:10:38PM +0800, Xingxing Luo wrote:
> When multiple threads are performing USB transmission, musb->lock will be
> unlocked when musb_giveback is executed. At this time, qh may be released
> in the dequeue process in other threads, resulting in a wild pointer, so
> it needs to be here get qh again, and judge whether qh is NULL, and when
> dequeue, you need to set qh to NULL.
> 
> Fixes: dbac5d07d13e ("usb: musb: host: don't start next rx urb if current one failed")
> Signed-off-by: Xingxing Luo <xingxing.luo@unisoc.com>
> ---
>  drivers/usb/musb/musb_host.c | 9 ++++++++-
>  1 file changed, 8 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/usb/musb/musb_host.c b/drivers/usb/musb/musb_host.c
> index a02c29216955..bc4507781167 100644
> --- a/drivers/usb/musb/musb_host.c
> +++ b/drivers/usb/musb/musb_host.c
> @@ -321,10 +321,16 @@ static void musb_advance_schedule(struct musb *musb, struct urb *urb,
>  	musb_giveback(musb, urb, status);
>  	qh->is_ready = ready;
>  
> +	/*
> +	 * musb->lock had been unlocked in musb_giveback, so qh may
> +	 * be freed, need to get it again
> +	 */
> +	qh = musb_ep_get_qh(hw_ep, is_in);
> +
>  	/* reclaim resources (and bandwidth) ASAP; deschedule it, and
>  	 * invalidate qh as soon as list_empty(&hep->urb_list)
>  	 */
> -	if (list_empty(&qh->hep->urb_list)) {
> +	if (qh && list_empty(&qh->hep->urb_list)) {
>  		struct list_head	*head;
>  		struct dma_controller	*dma = musb->dma_controller;
>  
> @@ -2398,6 +2404,7 @@ static int musb_urb_dequeue(struct usb_hcd *hcd, struct urb *urb, int status)
>  		 * and its URB list has emptied, recycle this qh.
>  		 */
>  		if (ready && list_empty(&qh->hep->urb_list)) {
> +			musb_ep_set_qh(qh->hw_ep, is_in, NULL);
>  			qh->hep->hcpriv = NULL;
>  			list_del(&qh->ring);
>  			kfree(qh);
> -- 
> 2.17.1
> 
> 

Hi,

This is the friendly patch-bot of Greg Kroah-Hartman.  You have sent him
a patch that has triggered this response.  He used to manually respond
to these common problems, but in order to save his sanity (he kept
writing the same thing over and over, yet to different people), I was
created.  Hopefully you will not take offence and will fix the problem
in your patch and resubmit it so that it can be accepted into the Linux
kernel tree.

You are receiving this message because of the following common error(s)
as indicated below:

- This looks like a new version of a previously submitted patch, but you
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  Please read the section entitled "The canonical patch format" in the
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If you wish to discuss this problem further, or you have questions about
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Greg will reply once he has dug out from the pending patches received
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thanks,

greg k-h's patch email bot