x86, vsyscall: fix the oops crash with __pa_vsymbol()
x86, vsyscall: fix the oops crash with __pa_vsymbol()

Appended patch fixes an oops while changing the vsyscall sysctl.
I am sure no one tested this code before integrating into mainline :(

BTW, using ioremap() in vsyscall_sysctl_change() to get the virtual
address of a kernel symbol sounds like an over kill.. I wonder if we
can define a simple __va_vsymbol() which will return directly the
kernel direct mapping. comments in the code which says gcc has trouble
with __va(__pa()) sounds bogus to me. __pa() on a vsyscall address will
not work anyhow :(

And also, the whole nop out syscall in vsyscall page infrastructure
(vsyscall_sysctl_change()) is added to make some attacks difficult,
and yet I don't see this nop out being done by default. This area
requires more cleanups?

Fix an oops with __pa_vsymbol(). VSYSCALL_FIRST_PAGE is a fixmap index.
We want the starting virtual address of the vsyscall page and not the index.

[ mingo: arch/x86 adaptation ]

Reported-by: Yanmin Zhang <5aa8ede52005e38a48fccf8ed843c06a1c45986c@intel.com>
Signed-off-by: Suresh Siddha <a42fd12510d3895be740fb89f87586733ee62f57@intel.com>
Signed-off-by: Ingo Molnar <9dbbbf0688fedc85ad4da37637f1a64b8c718ee2@elte.hu>
Signed-off-by: Thomas Gleixner <00e4cf8f46a57000a44449bf9dd8cbbcc209fd2a@linutronix.de>

TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs