On 27/07/16 19:08, Andrew Cooper wrote:
> Coverity identifies that __get_gfn_type_access() unconditionally writes to its
> type parameter under a number of circumstances.
>
> Signed-off-by: Andrew Cooper
Reviewed-by: George Dunlap
> ---
> CC: Jan Beulich
> CC: Tim Deegan
> CC: George Dunlap
> CC: Tamas K Lengyel
>
> There is a second complaint that ap2ma and p2ma are used before initialisation
> in the following line, although that is harder to reason about. I think the
> code is OK...
Well there are paths through __get_gfn_type_access() which don't set the
access value -- namely if p2m is null or
!paging_mode_translate(p2m->domain) (which coverity has no way of knowing).
That probably could use being made more robust at some point.
-George
> ---
> xen/arch/x86/mm/mem_sharing.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/xen/arch/x86/mm/mem_sharing.c b/xen/arch/x86/mm/mem_sharing.c
> index 47e0820..14952ce 100644
> --- a/xen/arch/x86/mm/mem_sharing.c
> +++ b/xen/arch/x86/mm/mem_sharing.c
> @@ -870,6 +870,7 @@ int mem_sharing_nominate_page(struct domain *d,
> unsigned int i;
> struct p2m_domain *ap2m;
> mfn_t amfn;
> +p2m_type_t ap2mt;
> p2m_access_t ap2ma;
>
> altp2m_list_lock(d);
> @@ -880,7 +881,7 @@ int mem_sharing_nominate_page(struct domain *d,
> if ( !ap2m )
> continue;
>
> -amfn = get_gfn_type_access(ap2m, gfn, NULL, &ap2ma, 0, NULL);
> +amfn = get_gfn_type_access(ap2m, gfn, &ap2mt, &ap2ma, 0, NULL);
> if ( mfn_valid(amfn) && (mfn_x(amfn) != mfn_x(mfn) || ap2ma !=
> p2ma) )
> {
> altp2m_list_unlock(d);
>
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