[libvirt] [PATCH] usb: Correct test for virUSBDeviceListSteal

[Laine Stump]

On 07/05/2013 02:23 AM, Gonglei (Arei) wrote:
> In the for loop, the if condition is always true, and will execute memmove.
> But it will cause the list->devs[i+1] overflow while i equals list->count-1.
>
> Signed-off-by: Gonglei <arei.gonglei at huawei.com>
> ---
>  src/util/virusb.c |    2 +-
>  1 files changed, 1 insertions(+), 1 deletions(-)
>
> diff --git a/src/util/virusb.c b/src/util/virusb.c
> index d34e44f..30d0b12 100644
> --- a/src/util/virusb.c
> +++ b/src/util/virusb.c
> @@ -497,7 +497,7 @@ virUSBDeviceListSteal(virUSBDeviceListPtr list,
>  
>          ret = list->devs[i];
>  
> -        if (i != list->count--)
> +        if (i != --list->count)
>              memmove(&list->devs[i],
>                      &list->devs[i+1],
>                      sizeof(*list->devs) * (list->count - i));

This function is a good candidate for switching to VIR_DELETE_ELEMENT()
instead. This will eliminate the bug that you found while making the
code much shorter. I have a patch for that sitting around, I'll rebase
it and post it.

(I actually have 15 patches that replace memmove+VIR_REALLOC() with
VIR_DELETE_ELEMENT and VIR_INSERT_ELEMENT. I had written them as
examples of VIR_*_ELEMENT and posted them, but was too nervous of
potential regression to push them (or even nag about reviews).