Commit message: drm/vc4: Return -EINVAL on the overflow checks failing.

By failing to set the errno, we'd continue on to trying to set up the
RCL, and then oops on trying to dereference the tile_bo that binning
validation should have set up.

Reported-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Eric Anholt <eric@anholt.net>
Fixes: d5b1a78a772f ("drm/vc4: Add support for drawing 3D frames.")
CVE: CVE-2017-5577
CWE: CWE-388
Vulnerability description: The vc4_get_bcl function in drivers/gpu/drm/vc4/vc4_gem.c in the VideoCore DRM driver in the Linux kernel before 4.9.7 does not set an errno value upon certain overflow detections, which allows local users to cause a denial of service (incorrect pointer dereference and OOPS) via inconsistent size values in a VC4_SUBMIT_CL ioctl call.

Project: linux
File: vc4_gem.c

vc4_get_bcl(struct drm_device *dev, struct vc4_exec_info *exec)
{
	struct drm_vc4_submit_cl *args = exec->args;
	void *temp = NULL;
	void *bin;
	int ret = 0;
	uint32_t bin_offset = 0;
	uint32_t shader_rec_offset = roundup(bin_offset + args->bin_cl_size,
					     16);
	uint32_t uniforms_offset = shader_rec_offset + args->shader_rec_size;
	uint32_t exec_size = uniforms_offset + args->uniforms_size;
	uint32_t temp_size = exec_size + (sizeof(struct vc4_shader_state) *
					  args->shader_rec_count);
	struct vc4_bo *bo;

	if (shader_rec_offset < args->bin_cl_size ||
	    uniforms_offset < shader_rec_offset ||
	    exec_size < uniforms_offset ||
	    args->shader_rec_count >= (UINT_MAX /
 					  sizeof(struct vc4_shader_state)) ||
 	    temp_size < exec_size) {
 		DRM_ERROR("overflow in exec arguments\n");
		ret = -EINVAL;
 		goto fail;
 	}
 
	/* Allocate space where we'll store the copied in user command lists
	 * and shader records.
	 *
	 * We don't just copy directly into the BOs because we need to
	 * read the contents back for validation, and I think the
	 * bo->vaddr is uncached access.
	 */
	temp = drm_malloc_ab(temp_size, 1);
	if (!temp) {
		DRM_ERROR("Failed to allocate storage for copying "
			  "in bin/render CLs.\n");
		ret = -ENOMEM;
		goto fail;
	}
	bin = temp + bin_offset;
	exec->shader_rec_u = temp + shader_rec_offset;
	exec->uniforms_u = temp + uniforms_offset;
	exec->shader_state = temp + exec_size;
	exec->shader_state_size = args->shader_rec_count;

	if (copy_from_user(bin,
			   (void __user *)(uintptr_t)args->bin_cl,
			   args->bin_cl_size)) {
		ret = -EFAULT;
		goto fail;
	}

	if (copy_from_user(exec->shader_rec_u,
			   (void __user *)(uintptr_t)args->shader_rec,
			   args->shader_rec_size)) {
		ret = -EFAULT;
		goto fail;
	}

	if (copy_from_user(exec->uniforms_u,
			   (void __user *)(uintptr_t)args->uniforms,
			   args->uniforms_size)) {
		ret = -EFAULT;
		goto fail;
	}

	bo = vc4_bo_create(dev, exec_size, true);
	if (IS_ERR(bo)) {
		DRM_ERROR("Couldn't allocate BO for binning\n");
		ret = PTR_ERR(bo);
		goto fail;
	}
	exec->exec_bo = &bo->base;

	list_add_tail(&to_vc4_bo(&exec->exec_bo->base)->unref_head,
		      &exec->unref_list);

	exec->ct0ca = exec->exec_bo->paddr + bin_offset;

	exec->bin_u = bin;

	exec->shader_rec_v = exec->exec_bo->vaddr + shader_rec_offset;
	exec->shader_rec_p = exec->exec_bo->paddr + shader_rec_offset;
	exec->shader_rec_size = args->shader_rec_size;

	exec->uniforms_v = exec->exec_bo->vaddr + uniforms_offset;
	exec->uniforms_p = exec->exec_bo->paddr + uniforms_offset;
	exec->uniforms_size = args->uniforms_size;

	ret = vc4_validate_bin_cl(dev,
				  exec->exec_bo->vaddr + bin_offset,
				  bin,
				  exec);
	if (ret)
		goto fail;

	ret = vc4_validate_shader_recs(dev, exec);
	if (ret)
		goto fail;

	/* Block waiting on any previous rendering into the CS's VBO,
	 * IB, or textures, so that pixels are actually written by the
	 * time we try to read them.
	 */
	ret = vc4_wait_for_seqno(dev, exec->bin_dep_seqno, ~0ull, true);

fail:
	drm_free_large(temp);
	return ret;
}