On Wed, Apr 18, 2018 at 07:42:56AM +0200, Gerd Hoffmann wrote:
> s/PAGE_SIZE/PAGE_MASK/
>
> Luckily release_offset is never larger than PAGE_SIZE, so the bug has no
> bad side effects and managed to stay unnoticed for years that way ...
>
> Signed-off-by: Gerd Hoffmann <kraxel@xxxxxxxxxx>
Sweeet. Since the buggy code uses the same expression for page frame and
offset I don't think there's a security bug. You might still want to cc:
stable (since without you defacto can't ever use this feature).
Reviewed-by: Daniel Vetter <daniel.vetter@xxxxxxxx>
> ---
> drivers/gpu/drm/qxl/qxl_ioctl.c | 4 ++--
> drivers/gpu/drm/qxl/qxl_release.c | 6 +++---
> 2 files changed, 5 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/gpu/drm/qxl/qxl_ioctl.c b/drivers/gpu/drm/qxl/qxl_ioctl.c
> index e238a1a2ec..6cc9f3367f 100644
> --- a/drivers/gpu/drm/qxl/qxl_ioctl.c
> +++ b/drivers/gpu/drm/qxl/qxl_ioctl.c
> @@ -182,9 +182,9 @@ static int qxl_process_single_command(struct qxl_device *qdev,
> goto out_free_reloc;
>
> /* TODO copy slow path code from i915 */
> - fb_cmd = qxl_bo_kmap_atomic_page(qdev, cmd_bo, (release->release_offset & PAGE_SIZE));
> + fb_cmd = qxl_bo_kmap_atomic_page(qdev, cmd_bo, (release->release_offset & PAGE_MASK));
> unwritten = __copy_from_user_inatomic_nocache
> - (fb_cmd + sizeof(union qxl_release_info) + (release->release_offset & ~PAGE_SIZE),
> + (fb_cmd + sizeof(union qxl_release_info) + (release->release_offset & ~PAGE_MASK),
> u64_to_user_ptr(cmd->command), cmd->command_size);
>
> {
> diff --git a/drivers/gpu/drm/qxl/qxl_release.c b/drivers/gpu/drm/qxl/qxl_release.c
> index 5d84a66fed..a0b4244d28 100644
> --- a/drivers/gpu/drm/qxl/qxl_release.c
> +++ b/drivers/gpu/drm/qxl/qxl_release.c
> @@ -411,10 +411,10 @@ union qxl_release_info *qxl_release_map(struct qxl_device *qdev,
> struct qxl_bo_list *entry = list_first_entry(&release->bos, struct qxl_bo_list, tv.head);
> struct qxl_bo *bo = to_qxl_bo(entry->tv.bo);
>
> - ptr = qxl_bo_kmap_atomic_page(qdev, bo, release->release_offset & PAGE_SIZE);
> + ptr = qxl_bo_kmap_atomic_page(qdev, bo, release->release_offset & PAGE_MASK);
> if (!ptr)
> return NULL;
> - info = ptr + (release->release_offset & ~PAGE_SIZE);
> + info = ptr + (release->release_offset & ~PAGE_MASK);
> return info;
> }
>
> @@ -426,7 +426,7 @@ void qxl_release_unmap(struct qxl_device *qdev,
> struct qxl_bo *bo = to_qxl_bo(entry->tv.bo);
> void *ptr;
>
> - ptr = ((void *)info) - (release->release_offset & ~PAGE_SIZE);
> + ptr = ((void *)info) - (release->release_offset & ~PAGE_MASK);
> qxl_bo_kunmap_atomic_page(qdev, bo, ptr);
> }
>
> --
> 2.9.3
>
> _______________________________________________
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> dri-devel@xxxxxxxxxxxxxxxxxxxxx
> https://lists.freedesktop.org/mailman/listinfo/dri-devel
--
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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