Re: [Xen-devel] [PATCH 2/2] libxl: zero the vtpm structures on allocation

[Daniel De Graaf <dgdegra@xxxxxxxxxxxxx>]

On 04/12/2013 10:10 AM, Ian Campbell wrote:
> On Thu, 2013-03-14 at 14:23 +0000, Daniel De Graaf wrote:
> > This avoids returning unallocated memory in the libxl_device_vtpm
> > structure since libxl_device_vtpm_init is not called here.
> Does the code not either loop over ndirs and initialise every one or
> alternatively fail and cleanup without returning the uninitialised
> memory?
The code used to initialize every member and so did not call the _init
function for vtpms; adding a new member to the structure causes this
to miss the new member. An alternative to this patch is to add a call
to libxl_device_vtpm_init inside the loop, similar the disk device type.
The nic device just does memset(nic, 0, sizeof(*nic)), like this patch.

> If this is an issue it expect it is an issue for libxl_device_*_list?
> Probably they should all be calling their respective init functions,
> perhaps via a new libxl_..._init_array helper?
At least disk and nic handle this on a per-element basis, so there's no
immediate advantage to an array helper.

> > Signed-off-by: Daniel De Graaf <dgdegra@xxxxxxxxxxxxx>
> > Cc:     Ian Jackson <ian.jackson@xxxxxxxxxxxxx>
> > Cc:     Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>
> > Cc:     Ian Campbell <ian.campbell@xxxxxxxxxx>
> > ---
> >   tools/libxl/libxl.c | 2 +-
> >   1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/tools/libxl/libxl.c b/tools/libxl/libxl.c
> > index e442afc..2b64700 100644
> > --- a/tools/libxl/libxl.c
> > +++ b/tools/libxl/libxl.c
> > @@ -1853,7 +1853,7 @@ libxl_device_vtpm *libxl_device_vtpm_list(libxl_ctx *ctx, 
> > uint32_t domid, int *n
> >       fe_path = libxl__sprintf(gc, "%s/device/vtpm", libxl__xs_get_dompath(gc, 
> > domid));
> >       dir = libxl__xs_directory(gc, XBT_NULL, fe_path, &ndirs);
> >       if(dir) {
> > -       vtpms = malloc(sizeof(*vtpms) * ndirs);
> > +       vtpms = calloc(sizeof(*vtpms), ndirs);
> >          libxl_device_vtpm* vtpm;
> >          libxl_device_vtpm* end = vtpms + ndirs;
> >          for(vtpm = vtpms; vtpm < end; ++vtpm, ++dir) {

--
Daniel De Graaf
National Security Agency

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