Re: [PATCH] memory: initialize 'fv' in MemoryRegionCache to make Coverity happy

[Stefan Hajnoczi <stefanha@gmail.com>]

On Mon, 9 Oct 2023 at 06:44, Ilya Maximets <i.maximets@ovn.org> wrote:
>
> Coverity scan reports multiple false-positive "defects" for the
> following series of actions in virtio.c:
>
>   MemoryRegionCache indirect_desc_cache;
>   address_space_cache_init_empty(&indirect_desc_cache);
>   address_space_cache_destroy(&indirect_desc_cache);
>
> For some reason it's unable to recognize the dependency between 'mrs.mr'
> and 'fv' and insists that '!mrs.mr' check in address_space_cache_destroy
> may take a 'false' branch, even though it is explicitly initialized to
> NULL in the address_space_cache_init_empty():
>
>   *** CID 1522371:  Memory - illegal accesses  (UNINIT)
>   /qemu/hw/virtio/virtio.c: 1627 in virtqueue_split_pop()
>   1621         }
>   1622
>   1623         vq->inuse++;
>   1624
>   1625         trace_virtqueue_pop(vq, elem, elem->in_num, elem->out_num);
>   1626     done:
>   >>>     CID 1522371:  Memory - illegal accesses  (UNINIT)
>   >>>     Using uninitialized value "indirect_desc_cache.fv" when
>   >>>     calling "address_space_cache_destroy".
>   1627         address_space_cache_destroy(&indirect_desc_cache);
>   1628
>   1629         return elem;
>   1630
>   1631     err_undo_map:
>   1632         virtqueue_undo_map_desc(out_num, in_num, iov);
>
>   ** CID 1522370:  Memory - illegal accesses  (UNINIT)
>
> Instead of trying to silence these false positive reports in 4
> different places, initializing 'fv' as well, as this doesn't result
> in any noticeable performance impact.
>
> Signed-off-by: Ilya Maximets <i.maximets@ovn.org>
> ---
>  include/exec/memory.h | 2 ++
>  1 file changed, 2 insertions(+)

Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>