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* [PATCH 4.19] drm/qxl: qxl_release use after free
@ 2020-05-04 11:36 Vasily Averin
  2020-05-04 16:39 ` Greg KH
  0 siblings, 1 reply; 2+ messages in thread
From: Vasily Averin @ 2020-05-04 11:36 UTC (permalink / raw)
  To: gregkh, stable; +Cc: Gerd Hoffmann

>From 933db73351d359f74b14f4af095808260aff11f9 Mon Sep 17 00:00:00 2001
From: Vasily Averin <vvs@virtuozzo.com>
Date: Wed, 29 Apr 2020 12:01:24 +0300
Subject: drm/qxl: qxl_release use after free

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 v.4.19 stable
Signed-off-by: Vasily Averin <vvs@virtuozzo.com>
---
 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(-)

diff --git a/drivers/gpu/drm/qxl/qxl_cmd.c b/drivers/gpu/drm/qxl/qxl_cmd.c
index 208af9f37914..be3eaf102fee 100644
--- a/drivers/gpu/drm/qxl/qxl_cmd.c
+++ b/drivers/gpu/drm/qxl/qxl_cmd.c
@@ -500,8 +500,8 @@ int qxl_hw_surface_alloc(struct qxl_device *qdev,
 	/* 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);
@@ -543,9 +543,8 @@ int qxl_hw_surface_dealloc(struct qxl_device *qdev,
 	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;
 }
diff --git a/drivers/gpu/drm/qxl/qxl_display.c b/drivers/gpu/drm/qxl/qxl_display.c
index 0570c6826bff..769e12b4c13c 100644
--- a/drivers/gpu/drm/qxl/qxl_display.c
+++ b/drivers/gpu/drm/qxl/qxl_display.c
@@ -532,8 +532,8 @@ static int qxl_primary_apply_cursor(struct drm_plane *plane)
 	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;
 
@@ -694,8 +694,8 @@ static void qxl_cursor_atomic_update(struct drm_plane *plane,
 	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);
@@ -740,8 +740,8 @@ static void qxl_cursor_atomic_disable(struct drm_plane *plane,
 	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,
diff --git a/drivers/gpu/drm/qxl/qxl_draw.c b/drivers/gpu/drm/qxl/qxl_draw.c
index 4d8681e84e68..958d0d870c99 100644
--- 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_fb_image *qxl_fb_image,
 		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)
@@ -381,8 +381,8 @@ void qxl_draw_dirty_fb(struct qxl_device *qdev,
 	}
 	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)
@@ -432,8 +432,8 @@ void qxl_draw_copyarea(struct qxl_device *qdev,
 	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)
@@ -476,8 +476,8 @@ void qxl_draw_fill(struct qxl_draw_fill *qxl_draw_fill_rec)
 
 	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)
diff --git a/drivers/gpu/drm/qxl/qxl_ioctl.c b/drivers/gpu/drm/qxl/qxl_ioctl.c
index 6cc9f3367fa0..5536b2f7b7b0 100644
--- 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(struct qxl_device *qdev,
 			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);
 
 out_free_bos:
 out_free_release:
-- 
2.17.1


^ permalink raw reply related	[flat|nested] 2+ messages in thread
* Re: [PATCH 4.19] drm/qxl: qxl_release use after free
  2020-05-04 11:36 [PATCH 4.19] drm/qxl: qxl_release use after free Vasily Averin
@ 2020-05-04 16:39 ` Greg KH
  0 siblings, 0 replies; 2+ messages in thread
From: Greg KH @ 2020-05-04 16:39 UTC (permalink / raw)
  To: Vasily Averin; +Cc: stable, Gerd Hoffmann

On Mon, May 04, 2020 at 02:36:27PM +0300, Vasily Averin wrote:
> >>From 933db73351d359f74b14f4af095808260aff11f9 Mon Sep 17 00:00:00 2001
> From: Vasily Averin <vvs@virtuozzo.com>
> Date: Wed, 29 Apr 2020 12:01:24 +0300
> Subject: drm/qxl: qxl_release use after free
> 
> 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 v.4.19 stable

Now replaced, thansk.

greg k-h

^ permalink raw reply	[flat|nested] 2+ messages in thread
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2020-05-04 11:36 [PATCH 4.19] drm/qxl: qxl_release use after free Vasily Averin
2020-05-04 16:39 ` Greg KH

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