From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from [140.186.70.92] (port=54834 helo=eggs.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1OYQhU-0007aE-Uh for qemu-devel@nongnu.org; Mon, 12 Jul 2010 17:38:09 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.69) (envelope-from ) id 1OYQhT-00069F-Lr for qemu-devel@nongnu.org; Mon, 12 Jul 2010 17:38:08 -0400 Received: from mail-yx0-f173.google.com ([209.85.213.173]:65139) by eggs.gnu.org with esmtp (Exim 4.69) (envelope-from ) id 1OYQhT-000696-IG for qemu-devel@nongnu.org; Mon, 12 Jul 2010 17:38:07 -0400 Received: by yxm8 with SMTP id 8so1226410yxm.4 for ; Mon, 12 Jul 2010 14:38:06 -0700 (PDT) Message-ID: <4C3B8B3E.6050504@codemonkey.ws> Date: Mon, 12 Jul 2010 16:38:06 -0500 From: Anthony Liguori MIME-Version: 1.0 References: <20100712174823.GA11411@redhat.com> <4C3B8409.9030202@codemonkey.ws> <20100712213023.GB13707@redhat.com> In-Reply-To: <20100712213023.GB13707@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 04:30 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. >> > It's the buffer guest allocated, and we leave it untouched. > How does this leak data? > Sorry, you're right. Reviewed-by: Anthony Liguori Regards, Anthony Liguori > >> 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"); >>>