drm/nouveau/secboot: remove VLA usage

In preparation to enabling -Wvla, remove VLA. In this particular
case directly use macro NVKM_MSGQUEUE_CMDLINE_SIZE instead of local
variable cmdline_size. Also, remove cmdline_size as it is not
actually useful anymore.

The use of stack Variable Length Arrays needs to be avoided, as they
can be a vector for stack exhaustion, which can be both a runtime bug
or a security flaw. Also, in general, as code evolves it is easy to
lose track of how big a VLA can get. Thus, we can end up having runtime
failures that are hard to debug.

Also, fixed as part of the directive to remove all VLAs from
the kernel: https://lkml.org/lkml/2018/3/7/621

Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
Reviewed-by: Thierry Reding <treding@nvidia.com>
Signed-off-by: Ben Skeggs <bskeggs@redhat.com>

diff --git a/drivers/gpu/drm/nouveau/nvkm/subdev/secboot/ls_ucode_msgqueue.c b/drivers/gpu/drm/nouveau/nvkm/subdev/secboot/ls_ucode_msgqueue.c
index 6f10b098676ce1a21e788e61a768d2a99a5860c3..1e1f1c635cabc468f1f44cb142c929805b427952 100644 (file)
--- a/drivers/gpu/drm/nouveau/nvkm/subdev/secboot/ls_ucode_msgqueue.c
+++ b/drivers/gpu/drm/nouveau/nvkm/subdev/secboot/ls_ucode_msgqueue.c
@@ -80,12 +80,11 @@ acr_ls_msgqueue_post_run(struct nvkm_msgqueue *queue,
                         struct nvkm_falcon *falcon, u32 addr_args)
 {
        struct nvkm_device *device = falcon->owner->device;
-       u32 cmdline_size = NVKM_MSGQUEUE_CMDLINE_SIZE;
-       u8 buf[cmdline_size];
+       u8 buf[NVKM_MSGQUEUE_CMDLINE_SIZE];
 
-       memset(buf, 0, cmdline_size);
+       memset(buf, 0, sizeof(buf));
        nvkm_msgqueue_write_cmdline(queue, buf);
-       nvkm_falcon_load_dmem(falcon, buf, addr_args, cmdline_size, 0);
+       nvkm_falcon_load_dmem(falcon, buf, addr_args, sizeof(buf), 0);
        /* rearm the queue so it will wait for the init message */
        nvkm_msgqueue_reinit(queue);