[PATCH 4.14 05/26] drm/qxl: qxl_release use after free

Greg Kroah-Hartman
2020-05-04T18:00:57Z

From: Vasily Averin <vvs@virtuozzo.com>

commit 933db73351d359f74b14f4af095808260aff11f9 upstream.

qxl_release should not be accesses after qxl_push_*_ring_release() calls:
userspace driver can process submitted command quickly, move qxl_release
into release_ring, generate interrupt and trigger garbage collector.

It can lead to crashes in qxl driver or trigger memory corruption
in some kmalloc-192 slab object

Gerd Hoffmann proposes to swap the qxl_release_fence_buffer_objects() +
qxl_push_{cursor,command}_ring_release() calls to close that race window.

cc: stable@vger.kernel.org
Fixes: f64122c1f6ad ("drm: add new QXL driver. (v1.4)")
Signed-off-by: Vasily Averin <vvs@virtuozzo.com>
Link: http://patchwork.freedesktop.org/patch/msgid/fa17b338-66ae-f299-68fe-8d32419d9071@virtuozzo.com
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
[backported to v4.14-stable]
Signed-off-by: Vasily Averin <vvs@virtuozzo.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
drivers/gpu/drm/qxl/qxl_cmd.c | 5 ++---
drivers/gpu/drm/qxl/qxl_display.c | 6 +++---
drivers/gpu/drm/qxl/qxl_draw.c | 8 ++++----
drivers/gpu/drm/qxl/qxl_ioctl.c | 5 +----
4 files changed, 10 insertions(+), 14 deletions(-)

--- a/drivers/gpu/drm/qxl/qxl_cmd.c
+++ b/drivers/gpu/drm/qxl/qxl_cmd.c
@@ -533,8 +533,8 @@ int qxl_hw_surface_alloc(struct qxl_devi
/* no need to add a release to the fence for this surface bo,
since it is only released when we ask to destroy the surface
and it would never signal otherwise */
- qxl_push_command_ring_release(qdev, release, QXL_CMD_SURFACE, false);
qxl_release_fence_buffer_objects(release);
+ qxl_push_command_ring_release(qdev, release, QXL_CMD_SURFACE, false);

surf->hw_surf_alloc = true;
spin_lock(&qdev->surf_id_idr_lock);
@@ -576,9 +576,8 @@ int qxl_hw_surface_dealloc(struct qxl_de
cmd->surface_id = id;
qxl_release_unmap(qdev, release, &cmd->release_info);

- qxl_push_command_ring_release(qdev, release, QXL_CMD_SURFACE, false);
-
qxl_release_fence_buffer_objects(release);
+ qxl_push_command_ring_release(qdev, release, QXL_CMD_SURFACE, false);

return 0;
}
--- a/drivers/gpu/drm/qxl/qxl_display.c
+++ b/drivers/gpu/drm/qxl/qxl_display.c
@@ -533,8 +533,8 @@ static int qxl_primary_apply_cursor(stru
cmd->u.set.visible = 1;
qxl_release_unmap(qdev, release, &cmd->release_info);

- qxl_push_cursor_ring_release(qdev, release, QXL_CMD_CURSOR, false);
qxl_release_fence_buffer_objects(release);
+ qxl_push_cursor_ring_release(qdev, release, QXL_CMD_CURSOR, false);

return ret;

@@ -701,8 +701,8 @@ static void qxl_cursor_atomic_update(str
cmd->u.position.y = plane->state->crtc_y + fb->hot_y;

qxl_release_unmap(qdev, release, &cmd->release_info);
- qxl_push_cursor_ring_release(qdev, release, QXL_CMD_CURSOR, false);
qxl_release_fence_buffer_objects(release);
+ qxl_push_cursor_ring_release(qdev, release, QXL_CMD_CURSOR, false);

if (old_cursor_bo)
qxl_bo_unref(&old_cursor_bo);
@@ -747,8 +747,8 @@ static void qxl_cursor_atomic_disable(st
cmd->type = QXL_CURSOR_HIDE;
qxl_release_unmap(qdev, release, &cmd->release_info);

- qxl_push_cursor_ring_release(qdev, release, QXL_CMD_CURSOR, false);
qxl_release_fence_buffer_objects(release);
+ qxl_push_cursor_ring_release(qdev, release, QXL_CMD_CURSOR, false);
}

static int qxl_plane_prepare_fb(struct drm_plane *plane,
--- a/drivers/gpu/drm/qxl/qxl_draw.c
+++ b/drivers/gpu/drm/qxl/qxl_draw.c
@@ -241,8 +241,8 @@ void qxl_draw_opaque_fb(const struct qxl
qxl_bo_physical_address(qdev, dimage->bo, 0);
qxl_release_unmap(qdev, release, &drawable->release_info);

- qxl_push_command_ring_release(qdev, release, QXL_CMD_DRAW, false);
qxl_release_fence_buffer_objects(release);
+ qxl_push_command_ring_release(qdev, release, QXL_CMD_DRAW, false);

out_free_palette:
if (palette_bo)
@@ -382,8 +382,8 @@ void qxl_draw_dirty_fb(struct qxl_device
}
qxl_bo_kunmap(clips_bo);

- qxl_push_command_ring_release(qdev, release, QXL_CMD_DRAW, false);
qxl_release_fence_buffer_objects(release);
+ qxl_push_command_ring_release(qdev, release, QXL_CMD_DRAW, false);

out_release_backoff:
if (ret)
@@ -433,8 +433,8 @@ void qxl_draw_copyarea(struct qxl_device
drawable->u.copy_bits.src_pos.y = sy;
qxl_release_unmap(qdev, release, &drawable->release_info);

- qxl_push_command_ring_release(qdev, release, QXL_CMD_DRAW, false);
qxl_release_fence_buffer_objects(release);
+ qxl_push_command_ring_release(qdev, release, QXL_CMD_DRAW, false);

out_free_release:
if (ret)
@@ -477,8 +477,8 @@ void qxl_draw_fill(struct qxl_draw_fill

qxl_release_unmap(qdev, release, &drawable->release_info);

- qxl_push_command_ring_release(qdev, release, QXL_CMD_DRAW, false);
qxl_release_fence_buffer_objects(release);
+ qxl_push_command_ring_release(qdev, release, QXL_CMD_DRAW, false);

out_free_release:
if (ret)
--- a/drivers/gpu/drm/qxl/qxl_ioctl.c
+++ b/drivers/gpu/drm/qxl/qxl_ioctl.c
@@ -257,11 +257,8 @@ static int qxl_process_single_command(st
apply_surf_reloc(qdev, &reloc_info[i]);
}

+ qxl_release_fence_buffer_objects(release);
ret = qxl_push_command_ring_release(qdev, release, cmd->type, true);
- if (ret)
- qxl_release_backoff_reserve_list(release);
- else
- qxl_release_fence_buffer_objects(release);