From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from [140.186.70.92] (port=54495 helo=eggs.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1OYQf8-0005ud-Co for qemu-devel@nongnu.org; Mon, 12 Jul 2010 17:35:43 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.69) (envelope-from ) id 1OYQf7-0005ru-Cj for qemu-devel@nongnu.org; Mon, 12 Jul 2010 17:35:42 -0400 Received: from mx1.redhat.com ([209.132.183.28]:39216) by eggs.gnu.org with esmtp (Exim 4.69) (envelope-from ) id 1OYQf7-0005rT-67 for qemu-devel@nongnu.org; Mon, 12 Jul 2010 17:35:41 -0400 Date: Tue, 13 Jul 2010 00:30:23 +0300 From: "Michael S. Tsirkin" Message-ID: <20100712213023.GB13707@redhat.com> References: <20100712174823.GA11411@redhat.com> <4C3B8409.9030202@codemonkey.ws> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4C3B8409.9030202@codemonkey.ws> 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: Anthony Liguori Cc: alex.williamson@redhat.com, qemu-devel@nongnu.org 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? > 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");