Xen devel - Nov 2013 - [PATCH RESEND] libxl: Do not generate short block in libxl__datacopier_prefixdata

Ages ago, Chunyan Liu writes:
> Tried the patch. It worked. Thanks.
Thanks.

IMO this patch should be considered for backporting, too.

Ian.

From 70f4755fba5e6a39e4f8ad55aff2d21f6aa8ff21 Mon Sep 17 00:00:00 2001
From: Ian Jackson <ian.jackson@eu.citrix.com>
Date: Tue, 3 Sep 2013 13:41:46 +0100
Subject: [PATCH] libxl: Do not generate short block in
 libxl__datacopier_prefixdata

libxl__datacopier_prefixdata would prepend a deliberately short block
(not just a half-full one, but one with a short buffer) to the
dc->bufs queue.  However, this is wrong because datacopier_readable
will find it and try to continue to fill it up.

Instead, allocate a full-sized buffer.

Signed-off-by: Ian Jackson <Ian.Jackson@eu.citrix.com>
Tested-by: Chunyan Liu <cyliu@suse.com>
---
 tools/libxl/libxl_aoutils.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/libxl/libxl_aoutils.c b/tools/libxl/libxl_aoutils.c
index 983a60a..b4eb6e5 100644
--- a/tools/libxl/libxl_aoutils.c
+++ b/tools/libxl/libxl_aoutils.c
@@ -89,7 +89,7 @@ void libxl__datacopier_prefixdata(libxl__egc *egc,
libxl__datacopier_state *dc,
 
     assert(len < dc->maxsz - dc->used);
 
-    buf = libxl__zalloc(NOGC, sizeof(*buf) - sizeof(buf->buf) + len);
+    buf = libxl__zalloc(NOGC, sizeof(*buf));
     buf->used = len;
     memcpy(buf->buf, data, len);
 
-- 
1.7.10.4

On Tue, 2013-11-12 at 16:49 +0000, Ian Jackson wrote:
> Ages ago, Chunyan Liu writes:
> > Tried the patch. It worked. Thanks.
> 
> Thanks.
> 
> IMO this patch should be considered for backporting, too.
> 
> Ian.
> 
> From 70f4755fba5e6a39e4f8ad55aff2d21f6aa8ff21 Mon Sep 17 00:00:00 2001
> From: Ian Jackson <ian.jackson@eu.citrix.com>
> Date: Tue, 3 Sep 2013 13:41:46 +0100
> Subject: [PATCH] libxl: Do not generate short block in
>  libxl__datacopier_prefixdata
> 
> libxl__datacopier_prefixdata would prepend a deliberately short block
> (not just a half-full one, but one with a short buffer) to the
> dc->bufs queue.  However, this is wrong because datacopier_readable
> will find it and try to continue to fill it up.
> 
> Instead, allocate a full-sized buffer.
> 
> Signed-off-by: Ian Jackson <Ian.Jackson@eu.citrix.com>
> Tested-by: Chunyan Liu <cyliu@suse.com>
Acked-by: Ian Campbell <ian.campbell@citrix.com>
> ---
>  tools/libxl/libxl_aoutils.c |    2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/tools/libxl/libxl_aoutils.c b/tools/libxl/libxl_aoutils.c
> index 983a60a..b4eb6e5 100644
> --- a/tools/libxl/libxl_aoutils.c
> +++ b/tools/libxl/libxl_aoutils.c
> @@ -89,7 +89,7 @@ void libxl__datacopier_prefixdata(libxl__egc *egc,
libxl__datacopier_state *dc,
>  
>      assert(len < dc->maxsz - dc->used);
>  
> -    buf = libxl__zalloc(NOGC, sizeof(*buf) - sizeof(buf->buf) + len);
> +    buf = libxl__zalloc(NOGC, sizeof(*buf));
>      buf->used = len;
>      memcpy(buf->buf, data, len);
>

Ian Campbell writes ("Re: [PATCH RESEND] libxl: Do not generate short block
in libxl__datacopier_prefixdata"):
> On Tue, 2013-11-12 at 16:49 +0000, Ian Jackson wrote:
> > From 70f4755fba5e6a39e4f8ad55aff2d21f6aa8ff21 Mon Sep 17 00:00:00 2001
> > From: Ian Jackson <ian.jackson@eu.citrix.com>
> > Date: Tue, 3 Sep 2013 13:41:46 +0100
> > Subject: [PATCH] libxl: Do not generate short block in
> >  libxl__datacopier_prefixdata
> > 
> > libxl__datacopier_prefixdata would prepend a deliberately short block
> > (not just a half-full one, but one with a short buffer) to the
> > dc->bufs queue.  However, this is wrong because datacopier_readable
> > will find it and try to continue to fill it up.
> > 
> > Instead, allocate a full-sized buffer.
> > 
> > Signed-off-by: Ian Jackson <Ian.Jackson@eu.citrix.com>
> > Tested-by: Chunyan Liu <cyliu@suse.com>
> 
> Acked-by: Ian Campbell <ian.campbell@citrix.com>
Thanks,

Committed-by: Ian Jackson <ian.jackson@eu.citrix.com>

I have put it on my backport list too.

Ian.

Ian Jackson writes ("Re: [PATCH RESEND] libxl: Do not generate short block
in libxl__datacopier_prefixdata"):
> Committed-by: Ian Jackson <ian.jackson@eu.citrix.com>
> 
> I have put it on my backport list too.
Now applied to 4.3, 4.2.  Was not applicable to 4.1.

Ian.