[PATCH 3/3] drm/tegra: Check size of a submitted command buffer

[Erik Faye-Lund]

On Fri, May 12, 2017 at 9:02 PM, Dmitry Osipenko <digetx at gmail.com> wrote:
> If command buffer claims a number of words that is higher than its BO can
> fit and a relocation lays past the BO, a kernel OOPS will be fired on that
> relocation address patching. This was triggered by an opentegra Xorg driver
> that erroneously pushed too many commands to the pushbuf.
>
> [   46.829393] Unable to handle kernel paging request at virtual address f09b2000
> ...
> [<c04a3ba4>] (host1x_job_pin) from [<c04dfcd0>] (tegra_drm_submit+0x474/0x510)
> [<c04dfcd0>] (tegra_drm_submit) from [<c04deea0>] (tegra_submit+0x50/0x6c)
> [<c04deea0>] (tegra_submit) from [<c04c07c0>] (drm_ioctl+0x1e4/0x3ec)
> [<c04c07c0>] (drm_ioctl) from [<c02541a0>] (do_vfs_ioctl+0x9c/0x8e4)
> [<c02541a0>] (do_vfs_ioctl) from [<c0254a1c>] (SyS_ioctl+0x34/0x5c)
> [<c0254a1c>] (SyS_ioctl) from [<c0107640>] (ret_fast_syscall+0x0/0x3c)
>
> Signed-off-by: Dmitry Osipenko <digetx at gmail.com>
> ---
>  drivers/gpu/drm/tegra/drm.c | 18 ++++++++++++++----
>  1 file changed, 14 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/gpu/drm/tegra/drm.c b/drivers/gpu/drm/tegra/drm.c
> index 732c8d98044f..e9c74a7780e7 100644
> --- a/drivers/gpu/drm/tegra/drm.c
> +++ b/drivers/gpu/drm/tegra/drm.c
> @@ -361,20 +361,30 @@ int tegra_drm_submit(struct tegra_drm_context *context,
>
>         while (num_cmdbufs) {
>                 struct drm_tegra_cmdbuf cmdbuf;
> -               struct host1x_bo *bo;
> +               struct drm_gem_object *gem;
> +               struct tegra_bo *bo;
>
>                 if (copy_from_user(&cmdbuf, cmdbufs, sizeof(cmdbuf))) {
>                         err = -EFAULT;
>                         goto fail;
>                 }
>
> -               bo = host1x_bo_lookup(file, cmdbuf.handle);
> -               if (!bo) {
> +               gem = drm_gem_object_lookup(file, cmdbuf.handle);
> +               if (!gem) {
>                         err = -ENOENT;
>                         goto fail;
>                 }
>
> -               host1x_job_add_gather(job, bo, cmdbuf.words, cmdbuf.offset);
> +               drm_gem_object_unreference_unlocked(gem);
> +
> +               if (cmdbuf.words * 4 > gem->size) {

Shouldn't this be "cmdbuf.offset + cmdbuf.words * 4 > gem->size"?