From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:54670) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ZQLoQ-0003PO-PZ for qemu-devel@nongnu.org; Fri, 14 Aug 2015 16:42:51 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1ZQLoM-0002Eq-PE for qemu-devel@nongnu.org; Fri, 14 Aug 2015 16:42:50 -0400 Received: from aserp1040.oracle.com ([141.146.126.69]:44526) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ZQLoM-0002EF-JA for qemu-devel@nongnu.org; Fri, 14 Aug 2015 16:42:46 -0400 Date: Fri, 14 Aug 2015 16:42:38 -0400 From: Konrad Rzeszutek Wilk Message-ID: <20150814204238.GA21854@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-Disposition: inline In-Reply-To: Subject: Re: [Qemu-devel] [PATCH v1 03/10] xen/pt: Check if reg->init function sets the 'data' past the reg->size List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Stefano Stabellini Cc: xen-devel@lists.xenproject.org, qemu-devel@nongnu.org, JBeulich@suse.com 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)? I couldnt' figure out how to make that work nicely. The QEMU_BUILD_BUG_ON look to be build time - not run-time. Which means that doing: for (i = 0; i < grp_entries; i++) { entries = grp_entries[i]... for (j = 0; j < entries; j++) QEMU_BUILD_BUG_ON(entries[j].init_val & ~size_mask) } is not something I can image the compiler working with? > > > > /* 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 > >