Re: [Qemu-devel] [PATCH] usb-storage: fix request canceling

[Paolo Bonzini]

Il 19/04/2012 11:46, Gerd Hoffmann ha scritto:
> Little fix for usb packet handling on i/o cancelation.  The
> usb packet pointer (s->packet) is cleared at the wrong place:
> The scsi request cancel handler does it.  When a usb packet
> is canceled the usb-storage emulation canceles the scsi request
> if present.  In most cases there is one, so usually s->packet
> is cleared as needed even with the code sitting at the wrong
> place.
> 
> If there is no scsi request in flight s->packet is not cleared
> though.  The usb-storage emulation will then try to complete an
> usb packet which is not in flight any more and thereby trigger
> an assert() in the usb core.
> 
> Fix this by clearing s->packet at the correct place, which is
> the usb packet cancel header.
> 
> Signed-off-by: Gerd Hoffmann <address@hidden>
> ---
>  hw/usb/dev-storage.c |    4 +++-
>  1 files changed, 3 insertions(+), 1 deletions(-)
> 
> diff --git a/hw/usb/dev-storage.c b/hw/usb/dev-storage.c
> index d865a5e..3d2f244 100644
> --- a/hw/usb/dev-storage.c
> +++ b/hw/usb/dev-storage.c
> @@ -268,7 +268,6 @@ static void usb_msd_request_cancelled(SCSIRequest *req)
>      if (req == s->req) {
>          scsi_req_unref(s->req);
>          s->req = NULL;
> -        s->packet = NULL;
>          s->scsi_len = 0;
>      }
>  }
> @@ -330,6 +329,9 @@ static void usb_msd_cancel_io(USBDevice *dev, USBPacket 
> *p)
>  {
>      MSDState *s = DO_UPCAST(MSDState, dev, dev);
>  
> +    assert(s->packet == p);
> +    s->packet = NULL;
> +
>      if (s->req) {
>          scsi_req_cancel(s->req);
>      }

Looks good,

Reviewed-by: Paolo Bonzini <address@hidden>