From mboxrd@z Thu Jan 1 00:00:00 1970 From: Konrad Rzeszutek Wilk Subject: Re: [PATCH v1 03/10] xen/pt: Check if reg->init function sets the 'data' past the reg->size Date: Fri, 17 Jul 2015 12:47:12 -0400 Message-ID: <20150717164712.GB19827__28393.1114864119$1437151718$gmane$org@l.oracle.com> References: <1435866681-18468-1-git-send-email-konrad.wilk@oracle.com> <1435866681-18468-4-git-send-email-konrad.wilk@oracle.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Received: from mail6.bemta5.messagelabs.com ([195.245.231.135]) by lists.xen.org with esmtp (Exim 4.72) (envelope-from ) id 1ZG8nC-0006xk-6h for xen-devel@lists.xenproject.org; Fri, 17 Jul 2015 16:47:22 +0000 Content-Disposition: inline In-Reply-To: List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org To: Stefano Stabellini Cc: xen-devel@lists.xenproject.org, qemu-devel@nongnu.org, JBeulich@suse.com List-Id: xen-devel@lists.xenproject.org On Fri, Jul 17, 2015 at 05:03:44PM +0100, Stefano Stabellini wrote: > On Thu, 2 Jul 2015, Konrad Rzeszutek Wilk wrote: > > It should never happen, but in case it does (an developer adds > > a new register and the 'init_val' expands past the register > > size) we want to report. The code will only write up to > > reg->size so there is no runtime danger of the register spilling > > across other ones - however to catch this sort of thing > > we still return an error. > > > > Signed-off-by: Konrad Rzeszutek Wilk > > --- > > hw/xen/xen_pt_config_init.c | 10 ++++++++-- > > 1 file changed, 8 insertions(+), 2 deletions(-) > > > > diff --git a/hw/xen/xen_pt_config_init.c b/hw/xen/xen_pt_config_init.c > > index 3938afd..09309ba 100644 > > --- a/hw/xen/xen_pt_config_init.c > > +++ b/hw/xen/xen_pt_config_init.c > > @@ -1904,9 +1904,15 @@ static int xen_pt_config_reg_init(XenPCIPassthroughState *s, > > } else > > val = data; > > > > + if (val & ~size_mask) { > > + XEN_PT_ERR(&s->dev,"Offset 0x%04x:0x%04x expands past register size(%d)!\n", > > + offset, val, reg->size); > > + g_free(reg_entry); > > + return -ENXIO; > > + } > > If we worry about changes to init_val, wouldn't it be better to add > QEMU_BUILD_BUG_ON(data & ~size_mask)? Duh. Yes :-) > > > > /* This could be just pci_set_long as we don't modify the bits > > - * past reg->size, but in case this routine is run in parallel > > - * we do not want to over-write other registers. */ > > + * past reg->size, but in case this routine is run in parallel or the > > + * init value is larger, we do not want to over-write registers. */ > > switch (reg->size) { > > case 1: pci_set_byte(s->dev.config + offset, (uint8_t)val); break; > > case 2: pci_set_word(s->dev.config + offset, (uint16_t)val); break; > > -- > > 2.1.0 > >