Re: [Qemu-devel] [PATCH v2 3/9] ccid-card-passthru: Assert on a stricter expression

[Marc-André Lureau]

Hi

On Thu, Feb 14, 2019 at 9:20 PM Philippe Mathieu-Daudé
<address@hidden> wrote:
>
> Suggested-by: Paolo Bonzini <address@hidden>
> Signed-off-by: Philippe Mathieu-Daudé <address@hidden>
> ---
>  hw/usb/ccid-card-passthru.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/hw/usb/ccid-card-passthru.c b/hw/usb/ccid-card-passthru.c
> index 1676b5fc05..0c44b38fc2 100644
> --- a/hw/usb/ccid-card-passthru.c
> +++ b/hw/usb/ccid-card-passthru.c
> @@ -270,7 +270,7 @@ static void ccid_card_vscard_read(void *opaque, const 
> uint8_t *buf, int size)
>      VSCMsgHeader *hdr;
>
>      assert(size <= VSCARD_IN_SIZE - card->vscard_in_pos);
> -    assert(card->vscard_in_hdr < VSCARD_IN_SIZE);
> +    assert(card->vscard_in_hdr < card->vscard_in_pos);


I think you need "<=".

card->vscard_in_hdr is updated in the loop and may reach card->vscard_in_pos:

    while ((card->vscard_in_pos - card->vscard_in_hdr >= sizeof(VSCMsgHeader))
         &&(card->vscard_in_pos - card->vscard_in_hdr >=
                                  sizeof(VSCMsgHeader) + ntohl(hdr->length))) {
...
        card->vscard_in_hdr += hdr->length + sizeof(VSCMsgHeader);
...
    }

if "hdr->length + sizeof(VSCMsgHeader)" == "card->vscard_in_pos -
card->vscard_in_hdr", card->vscard_in_hdr == card->vscard_in_pos after
the loop.


I think the existing assert() could also stay.

>      memcpy(card->vscard_in_data + card->vscard_in_pos, buf, size);
>      card->vscard_in_pos += size;
>      hdr = (VSCMsgHeader *)(card->vscard_in_data + card->vscard_in_hdr);
> --
> 2.20.1
>