Re: [Qemu-devel] [PATCH] net: rocker: fix an incorrect array bounds check

[Paolo Bonzini <pbonzini@redhat.com>]

On 22/12/2015 18:26, P J P wrote:
> +-- On Tue, 22 Dec 2015, Paolo Bonzini wrote --+
> | > -        if (++iovcnt > ROCKER_TX_FRAGS_MAX) {
> | > +        if (++iovcnt >= ROCKER_TX_FRAGS_MAX) {
> | 
> | Doesn't this forbid some valid ROCKER_TX_FRAGS_MAX-element iovecs?
> 
>   forbid..?  Sorry, I did not get the question.
> 
> | The check should be moved before the assignment to iov[iovcnt].iov_len.
> 
>   You mean like below..?
> 
> ===
> diff --git a/hw/net/rocker/rocker.c b/hw/net/rocker/rocker.c
> index c57f1a6..2e77e50 100644
> --- a/hw/net/rocker/rocker.c
> +++ b/hw/net/rocker/rocker.c
> @@ -232,6 +232,9 @@ static int tx_consume(Rocker *r, DescInfo *info)
>          frag_addr = rocker_tlv_get_le64(tlvs[ROCKER_TLV_TX_FRAG_ATTR_ADDR]);
>          frag_len = rocker_tlv_get_le16(tlvs[ROCKER_TLV_TX_FRAG_ATTR_LEN]);
>  
> +        if (iovcnt >= ROCKER_TX_FRAGS_MAX) {
> +            goto err_too_many_frags;
> +        }
>          iov[iovcnt].iov_len = frag_len;
>          iov[iovcnt].iov_base = g_malloc(frag_len);
>          if (!iov[iovcnt].iov_base) {
> @@ -244,10 +247,7 @@ static int tx_consume(Rocker *r, DescInfo *info)
>              err = -ROCKER_ENXIO;
>              goto err_bad_io;
>          }
> -
> -        if (++iovcnt > ROCKER_TX_FRAGS_MAX) {
> -            goto err_too_many_frags;
> -        }
> +        iovcnt++;
>      }
>  
>      if (iovcnt) {
> ===
> 
> Thank you.
> --
> Prasad J Pandit / Red Hat Product Security Team
> 47AF CE69 3A90 54AA 9045 1053 DD13 3D32 FE5B 041F
> 
> 

Yes, can you submit it as v2?

Paolo