This fixes a bug where userspace provided address is not fully mapped
and the kernel tries to read/write it while using PageTable fast page.
In the future userspace input should be copied on syscall entry, so
userspace could not modify the input during syscall. Currently there
is change that userspace input passes kernel syscall validation and
after that userspace could modify the input before the value is
actually used.
Bananymous
df260fe0e8