From mboxrd@z Thu Jan 1 00:00:00 1970 From: walter harms Date: Thu, 22 Oct 2015 11:52:38 +0000 Subject: Re: [patch] igbvf: integer overflow in igbvf_change_mtu() Message-Id: <5628CE06.4070601@bfs.de> List-Id: References: <20151022091013.GC9202@mwanda> In-Reply-To: <20151022091013.GC9202@mwanda> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: kernel-janitors@vger.kernel.org Am 22.10.2015 11:10, schrieb Dan Carpenter: > The "new_mtu" is between 0 and INT_MAX but when we add ETH_HLEN and > ETH_FCS_LEN to it then it could overflow so "max_frame" is negative. We > cap the upper bound of "max_frame" but we don't check for negative > values. This leads to a static checker warning. > > Signed-off-by: Dan Carpenter > > diff --git a/drivers/net/ethernet/intel/igbvf/netdev.c b/drivers/net/ethernet/intel/igbvf/netdev.c > index 297af80..fa338e0 100644 > --- a/drivers/net/ethernet/intel/igbvf/netdev.c > +++ b/drivers/net/ethernet/intel/igbvf/netdev.c > @@ -2350,7 +2350,7 @@ static struct net_device_stats *igbvf_get_stats(struct net_device *netdev) > static int igbvf_change_mtu(struct net_device *netdev, int new_mtu) > { > struct igbvf_adapter *adapter = netdev_priv(netdev); > - int max_frame = new_mtu + ETH_HLEN + ETH_FCS_LEN; > + unsigned int max_frame = new_mtu + ETH_HLEN + ETH_FCS_LEN; > > if (new_mtu < 68 || new_mtu > INT_MAX - ETH_HLEN - ETH_FCS_LEN || > max_frame > MAX_JUMBO_FRAME_SIZE) Perhaps it is better to use MAX_JUMBO_FRAME_SIZE. max_frame = new_mtu + ETH_HLEN + ETH_FCS_LEN = MAX_JUMBO_FRAME_SIZE // max valid new_mtu=MAX_JUMBO_FRAME_SIZE-ETH_HLEN-ETH_FCS_LEN so you can avoid adding a "new" variable INT_MAX into this context. Note: perhaps it would be better for the flow the check new_mtu before calculating max_frame. btw: can someone add a comment about the magic 68 ? is there something like a min_frame_size ? (it is a real question i have no idea) re, wh > -- > To unsubscribe from this list: send the line "unsubscribe kernel-janitors" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html >