drm/msm: Fix null pointer dereference on pointer edp

stable inclusion
from stable-v4.19.213
commit 7f642b93710b6b1119bdff90be01e6b5a2a5d669
category: bugfix
bugzilla: https://gitee.com/src-openeuler/kernel/issues/I9RB7E
CVE: CVE-2021-47445

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=7f642b93710b6b1119bdff90be01e6b5a2a5d669



--------------------------------

commit 2133c4fc upstream.

The initialization of pointer dev dereferences pointer edp before
edp is null checked, so there is a potential null pointer deference
issue. Fix this by only dereferencing edp after edp has been null
checked.

Addresses-Coverity: ("Dereference before null check")
Fixes: ab5b0107 ("drm/msm: Initial add eDP support in msm drm driver (v5)")
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Link: https://lore.kernel.org/r/20210929121857.213922-1-colin.king@canonical.com


Signed-off-by: Rob Clark <robdclark@chromium.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Liu Chuang <liuchuang40@huawei.com>