[PATCH v3 1/3] accel/amdxdna: refuse an I/O memory mapping of an imported BO

amdxdna_gem_obj_vmap() takes whatever dma_buf_vmap() returns and only
rejects a NULL vaddr. iosys_map is discriminated by is_iomem, so an
exporter answering with an I/O mapping leaves a void __iomem pointer in
abo->mem.kva, which amdxdna_cmd_set_error() memsets and memcpys through.

amdxdna_drm_va_tbl takes a dmabuf_fd, so such a BO can be any exporter's
buffer. amdgpu cannot reach this: its .pin forces GTT for a non peer to
peer attachment like ours. An exporter on drm_gem_prime_dmabuf_ops has
no .pin, and drm_gem_ttm_vmap() answers iomem for a VRAM resident
object, so an NPU paired with nouveau or radeon does.

Refuse the mapping. vmw_gem_vmap() does the same; unlike that one this
path is reachable from an unprivileged ioctl, so it does not warn.

Signed-off-by: Taimuraz Kaitmazov <[email protected]>
---
 drivers/accel/amdxdna/amdxdna_gem.c | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/drivers/accel/amdxdna/amdxdna_gem.c b/drivers/accel/amdxdna/amdxdna_gem.c
index 1f190b319bb..b66ec9e4828 100644
--- a/drivers/accel/amdxdna/amdxdna_gem.c
+++ b/drivers/accel/amdxdna/amdxdna_gem.c
@@ -683,10 +683,16 @@ static int amdxdna_gem_obj_vmap(struct drm_gem_object *obj, struct iosys_map *ma
 
 	dma_resv_assert_held(obj->resv);
 
-	if (is_import_bo(abo))
+	if (is_import_bo(abo)) {
 		ret = dma_buf_vmap(abo->dma_buf, map);
-	else
+		/* Callers use mem.kva as an ordinary kernel address. */
+		if (!ret && map->is_iomem) {
+			dma_buf_vunmap(abo->dma_buf, map);
+			return -EOPNOTSUPP;
+		}
+	} else {
 		ret = drm_gem_shmem_object_vmap(obj, map);
+	}
 	if (ret)
 		return ret;
 	if (!map->vaddr)
-- 
2.55.0