Xen devel - Nov 2013 - [PATCH] Fix ptr calculation when converting from a VA

From: Jean-Yves Migeon <jym@NetBSD.org>

The ptr calculation shall take the offset into the page into account
when ptr is valid.

Reported regression on NetBSD''s port-xen with last known working libxen
being rev 2.9. This corrupts the kernel symbol table when the table is
not loaded on a page boundary.

Issue was tracked down by FastIce and Jeff Rizzo. See also
http://mail-index.netbsd.org/port-xen/2013/10/16/msg008088.html

Signed-off-by: Jean-Yves Migeon <jym@NetBSD.org>
---
 tools/libxc/xc_dom.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/libxc/xc_dom.h b/tools/libxc/xc_dom.h
index a183e62..7099cee 100644
--- a/tools/libxc/xc_dom.h
+++ b/tools/libxc/xc_dom.h
@@ -342,7 +342,7 @@ static inline void *xc_dom_vaddr_to_ptr(struct xc_dom_image
*dom,
     if ( ptr == NULL )
         return ptr;
     *safe_region_out = (safe_region_count << XC_DOM_PAGE_SHIFT(dom)) -
offset;
-    return ptr;
+    return ptr + offset;
 }
 
 static inline xen_pfn_t xc_dom_p2m_host(struct xc_dom_image *dom, xen_pfn_t
pfn)
-- 
1.8.1.5

>>> On 29.11.13 at 11:39, <jym@NetBSD.org> wrote:
> From: Jean-Yves Migeon <jym@NetBSD.org>
> 
> The ptr calculation shall take the offset into the page into account
> when ptr is valid.
> 
> Reported regression on NetBSD''s port-xen with last known working
libxen
> being rev 2.9. This corrupts the kernel symbol table when the table is
> not loaded on a page boundary.
> 
> Issue was tracked down by FastIce and Jeff Rizzo. See also
> http://mail-index.netbsd.org/port-xen/2013/10/16/msg008088.html 
> 
> Signed-off-by: Jean-Yves Migeon <jym@NetBSD.org>
Reviewed-by: Jan Beulich <jbeulich@suse.com>
> ---
>  tools/libxc/xc_dom.h | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/tools/libxc/xc_dom.h b/tools/libxc/xc_dom.h
> index a183e62..7099cee 100644
> --- a/tools/libxc/xc_dom.h
> +++ b/tools/libxc/xc_dom.h
> @@ -342,7 +342,7 @@ static inline void *xc_dom_vaddr_to_ptr(struct 
> xc_dom_image *dom,
>      if ( ptr == NULL )
>          return ptr;
>      *safe_region_out = (safe_region_count << XC_DOM_PAGE_SHIFT(dom))
- offset;
> -    return ptr;
> +    return ptr + offset;
>  }
>  
>  static inline xen_pfn_t xc_dom_p2m_host(struct xc_dom_image *dom,
xen_pfn_t
> pfn)
> -- 
> 1.8.1.5
> 
> 
> _______________________________________________
> Xen-devel mailing list
> Xen-devel@lists.xen.org 
> http://lists.xen.org/xen-devel

On Fri, 2013-11-29 at 10:54 +0000, Jan Beulich wrote:
> >>> On 29.11.13 at 11:39, <jym@NetBSD.org> wrote:
> > From: Jean-Yves Migeon <jym@NetBSD.org>
> > 
> > The ptr calculation shall take the offset into the page into account
> > when ptr is valid.
> > 
> > Reported regression on NetBSD''s port-xen with last known
working libxen
> > being rev 2.9. This corrupts the kernel symbol table when the table is
> > not loaded on a page boundary.
> > 
> > Issue was tracked down by FastIce and Jeff Rizzo. See also
> > http://mail-index.netbsd.org/port-xen/2013/10/16/msg008088.html 
> > 
> > Signed-off-by: Jean-Yves Migeon <jym@NetBSD.org>
> 
> Reviewed-by: Jan Beulich <jbeulich@suse.com>
I see that Ian J also agreed this was correct in
<21139.14338.814627.156401@mariner.uk.xensource.com>.

Acked  + applied. Thanks everyone.