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 4.4-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-4.4 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. >From 933db73351d359f74b14f4af095808260aff11f9 Mon Sep 17 00:00:00 2001 From: Vasily Averin <vvs@xxxxxxxxxxxxx> Date: Wed, 29 Apr 2020 12:01:24 +0300 Subject: drm/qxl: qxl_release use after free From: Vasily Averin <vvs@xxxxxxxxxxxxx> 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: Vasily Averin <vvs@xxxxxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- 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 @@ -529,8 +529,8 @@ 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); @@ -572,9 +572,8 @@ 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 @@ -292,8 +292,8 @@ qxl_hide_cursor(struct qxl_device *qdev) 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); return 0; } @@ -390,8 +390,8 @@ static int qxl_crtc_cursor_set2(struct d 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); /* finish with the userspace bo */ ret = qxl_bo_reserve(user_bo, false); @@ -450,8 +450,8 @@ static int qxl_crtc_cursor_move(struct d cmd->u.position.y = qcrtc->cur_y + qcrtc->hot_spot_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); return 0; } --- a/drivers/gpu/drm/qxl/qxl_draw.c +++ b/drivers/gpu/drm/qxl/qxl_draw.c @@ -245,8 +245,8 @@ 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) @@ -385,8 +385,8 @@ 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) @@ -436,8 +436,8 @@ 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) @@ -480,8 +480,8 @@ 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); out_free_bos: out_free_release: Patches currently in stable-queue which might be from vvs@xxxxxxxxxxxxx are queue-4.4/drm-qxl-qxl_release-use-after-free.patch queue-4.4/drm-qxl-qxl_release-leak-in-qxl_draw_dirty_fb.patch