From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andrew Cooper Subject: Re: [PATCH v7 00/22] XSA55 libelf fixes for unstable Date: Wed, 12 Jun 2013 15:19:35 +0100 Message-ID: <51B88377.9040009@citrix.com> References: <1370974865-19554-1-git-send-email-ian.jackson@eu.citrix.com> <51B77ABA.20304@citrix.com> <20920.31638.988504.813293@mariner.uk.xensource.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20920.31638.988504.813293@mariner.uk.xensource.com> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org To: Ian Jackson Cc: "xen-devel@lists.xensource.com" , "mattjd@gmail.com" , "security@xen.org" List-Id: xen-devel@lists.xenproject.org On 12/06/13 14:45, Ian Jackson wrote: > Andrew Cooper writes ("Re: [PATCH v7 00/22] XSA55 libelf fixes for unstable"): >> On 11/06/13 19:20, Ian Jackson wrote: >>> This is version 7 of my series to try to fix libelf and the domain >>> loader. >> Fantastic. This entire series is now >> >> Reviewed-by: Andrew Cooper > Great, thanks. The 4.1 backports are a work in progress. > > I have had a review from Oracle by private email. Prompted by that > review I did a search and now I'm suspicious of a range test in > xc_dom_alloc_segment. > > I'm considering adding the patch below to the end of my series. > > Ian. > > > Subject: libxc: Better range check in xc_dom_alloc_segment > > If seg->pfn is too large, the arithmetic in the range check might > overflow, defeating the range check. > > This is part of the fix to a security issue, XSA-55. > > Signed-off-by: Ian Jackson Wow - yes that does need fixing. It is the same sort of argument as for the extra changes to patch 22. Reviewed-by: Andrew Cooper > > diff --git a/tools/libxc/xc_dom_core.c b/tools/libxc/xc_dom_core.c > index bf05d2a..9c0a52c 100644 > --- a/tools/libxc/xc_dom_core.c > +++ b/tools/libxc/xc_dom_core.c > @@ -510,7 +510,8 @@ int xc_dom_alloc_segment(struct xc_dom_image *dom, > seg->vstart = start; > seg->pfn = (seg->vstart - dom->parms.virt_base) / page_size; > > - if ( pages > dom->total_pages || /* double test avoids overflow probs */ > + if ( pages > dom->total_pages || /* multiple test avoids overflow probs */ > + seg->pfn > dom->total_pages || > pages > dom->total_pages - seg->pfn) > { > xc_dom_panic(dom->xch, XC_OUT_OF_MEMORY,