drm/nouveau/dispnv04: fix null pointer dereference in nv17_tv_get_hd_modes

stable inclusion
from stable-v4.19.317
commit ffabad4aa91e33ced3c6ae793fb37771b3e9cb51
category: bugfix
bugzilla: https://gitee.com/src-openeuler/kernel/issues/IAGEON
CVE: CVE-2024-41089

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=ffabad4aa91e33ced3c6ae793fb37771b3e9cb51



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commit 6d411c8ccc0137a612e0044489030a194ff5c843 upstream.

In nv17_tv_get_hd_modes(), the return value of drm_mode_duplicate() is
assigned to mode, which will lead to a possible NULL pointer dereference
on failure of drm_mode_duplicate(). The same applies to drm_cvt_mode().
Add a check to avoid null pointer dereference.

Cc: stable@vger.kernel.org
Signed-off-by: Ma Ke <make24@iscas.ac.cn>
Signed-off-by: Lyude Paul <lyude@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240625081029.2619437-1-make24@iscas.ac.cn


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Liu Mingrui <liumingrui@huawei.com>