fbdev: imxfb: Check fb_add_videomode to prevent null-ptr-deref

Vulnerability Description

In the Linux kernel, the following vulnerability has been resolved: fbdev: imxfb: Check fb_add_videomode to prevent null-ptr-deref fb_add_videomode() can fail with -ENOMEM when its internal kmalloc() cannot allocate a struct fb_modelist. If that happens, the modelist stays empty but the driver continues to register. Add a check for its return value to prevent poteintial null-ptr-deref, which is similar to the commit 17186f1f90d3 ("fbdev: Fix do_register_framebuffer to prevent null-ptr-deref in fb_videomode_to_var").

References

• https://git.kernel.org/stable/c/69373502c2b5d364842c702c941d1171e4f35a7c
• https://git.kernel.org/stable/c/f00c29e6755ead56baf2a9c1d3c4c0bb40af3612
• https://git.kernel.org/stable/c/cca8f5a3991916729b39d797d01499c335137319
• https://git.kernel.org/stable/c/ac16154cccda8be10ee3ae188f10a06f3890bc5d
• https://git.kernel.org/stable/c/4b5d36cc3014986e6fac12eaa8433fe56801d4ce
• https://git.kernel.org/stable/c/40f0a51f6c54d46a94b9f1180339ede7ca7ee190
• https://git.kernel.org/stable/c/49377bac9e3bec1635065a033c9679214fe7593e
• https://git.kernel.org/stable/c/f060441c153495750804133555cf0a211a856892
• https://git.kernel.org/stable/c/da11e6a30e0bb8e911288bdc443b3dc8f6a7cac7