From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from [140.186.70.92] (port=37189 helo=eggs.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1OYRz4-00008Q-NF for qemu-devel@nongnu.org; Mon, 12 Jul 2010 19:00:23 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.69) (envelope-from ) id 1OYRz3-0007tB-8J for qemu-devel@nongnu.org; Mon, 12 Jul 2010 19:00:22 -0400 Received: from mail-qy0-f173.google.com ([209.85.216.173]:41975) by eggs.gnu.org with esmtp (Exim 4.69) (envelope-from ) id 1OYRz2-0007t0-UH for qemu-devel@nongnu.org; Mon, 12 Jul 2010 19:00:21 -0400 Received: by qyk7 with SMTP id 7so1672531qyk.4 for ; Mon, 12 Jul 2010 16:00:20 -0700 (PDT) Message-ID: <4C3B9E84.3050809@codemonkey.ws> Date: Mon, 12 Jul 2010 18:00:20 -0500 From: Anthony Liguori MIME-Version: 1.0 References: <20100712174823.GA11411@redhat.com> <4C3B8409.9030202@codemonkey.ws> <20100712224254.GD13707@redhat.com> In-Reply-To: <20100712224254.GD13707@redhat.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Subject: [Qemu-devel] Re: [PATCH RFC] e1000: fix access 4 bytes beyond buffer end List-Id: qemu-devel.nongnu.org List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: "Michael S. Tsirkin" Cc: alex.williamson@redhat.com, qemu-devel@nongnu.org On 07/12/2010 05:42 PM, Michael S. Tsirkin wrote: > On Mon, Jul 12, 2010 at 04:07:21PM -0500, Anthony Liguori wrote: > >> On 07/12/2010 12:48 PM, Michael S. Tsirkin wrote: >> >>> We do range check for size, and get size as buffer, >>> but copy size + 4 bytes (4 is for FCS). >>> Let's copy size bytes but put size + 4 in length. >>> >>> Signed-off-by: Michael S. Tsirkin >>> >> I think I'd feel slightly better if we zero'd out the FCS before >> writing it to the guest. It is potentially a data leak. >> >> Regards, >> >> Anthony Liguori >> > I am guessing there's no chance guest actually looks > at this data, otherwise it won't match and we'd get errors, right? > That's my assumption too. Although I believe there are some known issues with e1000 and certain versions of Windows and the Microsoft built-in driver. Maybe this is why those drivers don't work and the Intel drivers do? Regards, Anthony Liguori >>> --- >>> >>> Anthony, Alex, please review. >>> >>> hw/e1000.c | 3 +-- >>> 1 files changed, 1 insertions(+), 2 deletions(-) >>> >>> diff --git a/hw/e1000.c b/hw/e1000.c >>> index 0da65f9..70aba11 100644 >>> --- a/hw/e1000.c >>> +++ b/hw/e1000.c >>> @@ -649,7 +649,6 @@ e1000_receive(VLANClientState *nc, const uint8_t *buf, size_t size) >>> } >>> >>> rdh_start = s->mac_reg[RDH]; >>> - size += 4; // for the header >>> do { >>> if (s->mac_reg[RDH] == s->mac_reg[RDT]&& s->check_rxov) { >>> set_ics(s, 0, E1000_ICS_RXO); >>> @@ -663,7 +662,7 @@ e1000_receive(VLANClientState *nc, const uint8_t *buf, size_t size) >>> if (desc.buffer_addr) { >>> cpu_physical_memory_write(le64_to_cpu(desc.buffer_addr), >>> (void *)(buf + vlan_offset), size); >>> - desc.length = cpu_to_le16(size); >>> + desc.length = cpu_to_le16(size + 4 /* for FCS */); >>> desc.status |= E1000_RXD_STAT_EOP|E1000_RXD_STAT_IXSM; >>> } else // as per intel docs; skip descriptors with null buf addr >>> DBGOUT(RX, "Null RX descriptor!!\n"); >>>