Re: [PATCH v1 2/2] xen: mapcache: Fix unmapping of first entries in buckets

[Stefano Stabellini]

On Tue, 2 Jul 2024, Edgar E. Iglesias wrote:
> From: "Edgar E. Iglesias" <edgar.iglesias@amd.com>
> 
> This fixes the clobbering of the entry->next pointer when
> unmapping the first entry in a bucket of a mapcache.
> 
> Fixes: 123acd816d ("xen: mapcache: Unmap first entries in buckets")
> Reported-by: Anthony PERARD <anthony.perard@vates.tech>
> Signed-off-by: Edgar E. Iglesias <edgar.iglesias@amd.com>

Reviewed-by: Stefano Stabellini <sstabellini@kernel.org>


> ---
>  hw/xen/xen-mapcache.c | 12 +++++++++++-
>  1 file changed, 11 insertions(+), 1 deletion(-)
> 
> diff --git a/hw/xen/xen-mapcache.c b/hw/xen/xen-mapcache.c
> index 5f23b0adbe..18ba7b1d8f 100644
> --- a/hw/xen/xen-mapcache.c
> +++ b/hw/xen/xen-mapcache.c
> @@ -597,7 +597,17 @@ static void 
> xen_invalidate_map_cache_entry_unlocked(MapCache *mc,
>          pentry->next = entry->next;
>          g_free(entry);
>      } else {
> -        memset(entry, 0, sizeof *entry);
> +        /*
> +         * Invalidate mapping but keep entry->next pointing to the rest
> +         * of the list.
> +         *
> +         * Note that lock is already zero here, otherwise we don't unmap.
> +         */
> +        entry->paddr_index = 0;
> +        entry->vaddr_base = NULL;
> +        entry->valid_mapping = NULL;
> +        entry->flags = 0;
> +        entry->size = 0;
>      }
>  }
>  
> -- 
> 2.43.0
>