Re: [PATCH v2 04/10] KVM: arm/arm64: vgic-its: Check GITS_BASER Valid bit before saving tables

Andre Przywara
2017-10-06T14:38:05Z

Hi,

On 27/09/17 14:28, Eric Auger wrote:
> At the moment we don't properly check the GITS_BASER<n>.Valid
> bit before saving the collection and device tables.
>
> On Collection table save() we use the gpa field whereas the Valid bit
> should be used. On device table save() there is no check. This can
> cause various bugs, among which a subsequent fault when accessing
> the table in guest memory.
>
> Let's systematically check the Valid bit before doing anything.
>
> We also unifomize the code between save and restore.

uniformize

Apart from that:

> Signed-off-by: Eric Auger <eric.auger@redhat.com>

Reviewed-by: Andre Przywara <andre.przywara@arm.com>

Cheers,
Andre.

> ---
> virt/kvm/arm/vgic/vgic-its.c | 20 +++++++++++---------
> 1 file changed, 11 insertions(+), 9 deletions(-)
>
> diff --git a/virt/kvm/arm/vgic/vgic-its.c b/virt/kvm/arm/vgic/vgic-its.c
> index c1f7972..60ecf91 100644
> --- a/virt/kvm/arm/vgic/vgic-its.c
> +++ b/virt/kvm/arm/vgic/vgic-its.c
> @@ -2067,11 +2067,12 @@ static int vgic_its_device_cmp(void *priv, struct list_head *a,
> static int vgic_its_save_device_tables(struct vgic_its *its)
> {
> const struct vgic_its_abi *abi = vgic_its_get_abi(its);
> + u64 baser = its->baser_device_table;
> struct its_device *dev;
> int dte_esz = abi->dte_esz;
> - u64 baser;
>
> - baser = its->baser_device_table;
> + if (!(baser & GITS_BASER_VALID))
> + return 0;
>
> list_sort(NULL, &its->device_list, vgic_its_device_cmp);
>
> @@ -2217,17 +2218,17 @@ static int vgic_its_restore_cte(struct vgic_its *its, gpa_t gpa, int esz)
> static int vgic_its_save_collection_table(struct vgic_its *its)
> {
> const struct vgic_its_abi *abi = vgic_its_get_abi(its);
> + u64 baser = its->baser_coll_table;
> + gpa_t gpa = BASER_ADDRESS(baser);
> struct its_collection *collection;
> u64 val;
> - gpa_t gpa;
> size_t max_size, filled = 0;
> int ret, cte_esz = abi->cte_esz;
>
> - gpa = BASER_ADDRESS(its->baser_coll_table);
> - if (!gpa)
> + if (!(baser & GITS_BASER_VALID))
> return 0;
>
> - max_size = GITS_BASER_NR_PAGES(its->baser_coll_table) * SZ_64K;
> + max_size = GITS_BASER_NR_PAGES(baser) * SZ_64K;
>
> list_for_each_entry(collection, &its->collection_list, coll_list) {
> ret = vgic_its_save_cte(its, collection, gpa, cte_esz);
> @@ -2258,17 +2259,18 @@ static int vgic_its_save_collection_table(struct vgic_its *its)
> static int vgic_its_restore_collection_table(struct vgic_its *its)
> {
> const struct vgic_its_abi *abi = vgic_its_get_abi(its);
> + u64 baser = its->baser_coll_table;
> int cte_esz = abi->cte_esz;
> size_t max_size, read = 0;
> gpa_t gpa;
> int ret;
>
> - if (!(its->baser_coll_table & GITS_BASER_VALID))
> + if (!(baser & GITS_BASER_VALID))
> return 0;
>
> - gpa = BASER_ADDRESS(its->baser_coll_table);
> + gpa = BASER_ADDRESS(baser);
>
> - max_size = GITS_BASER_NR_PAGES(its->baser_coll_table) * SZ_64K;
> + max_size = GITS_BASER_NR_PAGES(baser) * SZ_64K;
>
> while (read < max_size) {
> ret = vgic_its_restore_cte(its, gpa, cte_esz);
>