This is a note to let you know that I've just added the patch titled drm/qxl: qxl_release use after free to the 5.6-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: drm-qxl-qxl_release-use-after-free.patch and it can be found in the queue-5.6 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. commit 2b3ea4fa076e0e1907351d6c2e499f29fc289532 Author: Vasily Averin <vvs@xxxxxxxxxxxxx> Date: Wed Apr 29 12:01:24 2020 +0300 drm/qxl: qxl_release use after free 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@xxxxxxxxxxxxxxx Fixes: f64122c1f6ad ("drm: add new QXL driver. (v1.4)") Signed-off-by: Vasily Averin <vvs@xxxxxxxxxxxxx> Link: http://patchwork.freedesktop.org/patch/msgid/fa17b338-66ae-f299-68fe-8d32419d9071@xxxxxxxxxxxxx Signed-off-by: Gerd Hoffmann <kraxel@xxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> diff --git a/drivers/gpu/drm/qxl/qxl_cmd.c b/drivers/gpu/drm/qxl/qxl_cmd.c index dc9af6ac3cc4e..d082c194ccccf 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 16d73b22f3f54..92d84280096e0 100644 --- a/drivers/gpu/drm/qxl/qxl_display.c +++ b/drivers/gpu/drm/qxl/qxl_display.c @@ -523,8 +523,8 @@ 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; @@ -665,8 +665,8 @@ 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 != NULL) qxl_bo_unpin(old_cursor_bo); @@ -713,8 +713,8 @@ 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 void qxl_update_dumb_head(struct qxl_device *qdev, diff --git a/drivers/gpu/drm/qxl/qxl_draw.c b/drivers/gpu/drm/qxl/qxl_draw.c index f8776d60d08e2..3599db096973e 100644 --- a/drivers/gpu/drm/qxl/qxl_draw.c +++ b/drivers/gpu/drm/qxl/qxl_draw.c @@ -243,8 +243,8 @@ 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) diff --git a/drivers/gpu/drm/qxl/qxl_ioctl.c b/drivers/gpu/drm/qxl/qxl_ioctl.c index 8117a45b36102..72f3f1bbb40c1 100644 --- a/drivers/gpu/drm/qxl/qxl_ioctl.c +++ b/drivers/gpu/drm/qxl/qxl_ioctl.c @@ -261,11 +261,8 @@ 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: