drm/nouveau/dispnv04: fix null pointer dereference in nv17_tv_get_ld_modes

stable inclusion
from stable-v4.19.317
commit 9289cd3450d1da3e271ef4b054d4d2932c41243e
category: bugfix
bugzilla: https://gitee.com/src-openeuler/kernel/issues/IAGENV
CVE: CVE-2024-41095

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=9289cd3450d1da3e271ef4b054d4d2932c41243e



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commit 66edf3fb331b6c55439b10f9862987b0916b3726 upstream.

In nv17_tv_get_ld_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(). Add a check to avoid npd.

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/20240625081828.2620794-1-make24@iscas.ac.cn


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Yuan Can <yuancan@huawei.com>