[lineage-20] Fix CVE-2021-3968

[Flamefire]

As described in #66 this is the minimal approach to fix CVE-2021-3968 (with 2 simple commits first for extra safety)

Upstream those are:

• Commits dd0859dccbe291cf8179a96390f5c0e45cb9af1d & ca97d939db114c8d1619e10a3b82af8615372dae for readonly hooks
• 3dfc9b02864b19f4dab376f14479ee4ad1de6c9e to add new hooks without explicitly adding them (another time)
• Add a new hook in 3ec30113264a7bcd389f51d1738e42da0f41bb5a used to fix the CVE with 11db2de0a

First there are 4 commits required for the others to work from https://github.com/Flamefire/android_kernel_sony_msm8998/pull/15

See #67 where this comes from but I figure you want that to go onto lineage-20

[derfelot]

Thanks