From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andrew Cooper Subject: Re: [PATCH 02/22] libxc: introduce xc_dom_seg_to_ptr_pages Date: Mon, 10 Jun 2013 13:21:51 +0100 Message-ID: <51B5C4DF.2050002@citrix.com> References: <1370629642-6990-1-git-send-email-ian.jackson@eu.citrix.com> <1370629642-6990-3-git-send-email-ian.jackson@eu.citrix.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <1370629642-6990-3-git-send-email-ian.jackson@eu.citrix.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 07/06/13 19:27, Ian Jackson wrote: > Provide a version of xc_dom_seg_to_ptr which returns the number of > guest pages it has actually mapped. This is useful for callers who > want to do range checking; we will use this later in this series. > > This is part of the fix to a security issue, XSA-55. > > Signed-off-by: Ian Jackson > > v5: xc_dom_seg_to_ptr_pages sets *pages_out=0 if it returns NULL. > > v4 was: > > Acked-by: Ian Campbell > Reviewed-by: Konrad Rzeszutek Wilk With a view to security, why does this change need to be present? At the end of the v6 series, this new function has 1 caller from xc_dom_load_elf_kernel() and 5 callers of the original function. >>From looking at the semantics of the function, it either returns NULL, or maps all requested pages (xc_dom_seg size rounded up to the nearest page) With that in mind, xc_dom_load_elf_kernel() can calculate elf->dest_size given a successful mapping from xc_dom_seg_to_ptr(), without needing this _pages() variant. As a result, I do not think it is needed to put this change in, unless I am missing something about the semantics. ~Andrew > --- > tools/libxc/xc_dom.h | 18 +++++++++++++++--- > 1 files changed, 15 insertions(+), 3 deletions(-) > > diff --git a/tools/libxc/xc_dom.h b/tools/libxc/xc_dom.h > index ac36600..da0598c 100644 > --- a/tools/libxc/xc_dom.h > +++ b/tools/libxc/xc_dom.h > @@ -294,14 +294,26 @@ void *xc_dom_pfn_to_ptr(struct xc_dom_image *dom, xen_pfn_t first, > void xc_dom_unmap_one(struct xc_dom_image *dom, xen_pfn_t pfn); > void xc_dom_unmap_all(struct xc_dom_image *dom); > > -static inline void *xc_dom_seg_to_ptr(struct xc_dom_image *dom, > - struct xc_dom_seg *seg) > +static inline void *xc_dom_seg_to_ptr_pages(struct xc_dom_image *dom, > + struct xc_dom_seg *seg, > + xen_pfn_t *pages_out) > { > xen_vaddr_t segsize = seg->vend - seg->vstart; > unsigned int page_size = XC_DOM_PAGE_SIZE(dom); > xen_pfn_t pages = (segsize + page_size - 1) / page_size; > + void *retval; > + > + retval = xc_dom_pfn_to_ptr(dom, seg->pfn, pages); > + > + if ( pages_out != NULL ) > + *pages_out = retval ? pages : 0; > + return retval; > +} > > - return xc_dom_pfn_to_ptr(dom, seg->pfn, pages); > +static inline void *xc_dom_seg_to_ptr(struct xc_dom_image *dom, > + struct xc_dom_seg *seg) > +{ > + return xc_dom_seg_to_ptr_pages(dom, seg, NULL); > } > > static inline void *xc_dom_vaddr_to_ptr(struct xc_dom_image *dom,