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drm/qxl: qxl_release use after free

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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: f64122c1f6 ("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>
This commit is contained in:
Vasily Averin
2020-04-29 12:01:24 +03:00
committed by Gerd Hoffmann
parent 5b5703dbaf
commit 933db73351
4 changed files with 7 additions and 11 deletions
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5
drivers/gpu/drm/qxl/qxl_ioctl.c
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@@ -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: