Re: [PATCH v2] hw/net/net_tx_pkt: fix assertion failure in net_tx_pkt_add_raw_fragment()

[Dmitry Fleytman <dmitry.fleytman@gmail.com>]

> On 1 Aug 2020, at 19:42, Mauro Matteo Cascella <mcascell@redhat.com> wrote:
> 
> An assertion failure issue was found in the code that processes network packets
> while adding data fragments into the packet context. It could be abused by a
> malicious guest to abort the QEMU process on the host. This patch replaces the
> affected assert() with a conditional statement, returning false if the current
> data fragment exceeds max_raw_frags.
> 


Reviewed-by: Dmitry Fleytman <dmitry.fleytman@gmail.com>


> Reported-by: Alexander Bulekov <alxndr@bu.edu>
> Reported-by: Ziming Zhang <ezrakiez@gmail.com>
> Signed-off-by: Mauro Matteo Cascella <mcascell@redhat.com>
> ---
> hw/net/net_tx_pkt.c | 5 ++++-
> 1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/hw/net/net_tx_pkt.c b/hw/net/net_tx_pkt.c
> index 9560e4a49e..da262edc3e 100644
> --- a/hw/net/net_tx_pkt.c
> +++ b/hw/net/net_tx_pkt.c
> @@ -379,7 +379,10 @@ bool net_tx_pkt_add_raw_fragment(struct NetTxPkt *pkt, hwaddr pa,
>     hwaddr mapped_len = 0;
>     struct iovec *ventry;
>     assert(pkt);
> -    assert(pkt->max_raw_frags > pkt->raw_frags);
> +
> +    if (pkt->raw_frags >= pkt->max_raw_frags) {
> +        return false;
> +    }
> 
>     if (!len) {
>         return true;
> -- 
> 2.26.2
>