x86/vsyscall_emu/64: Don't use RET in vsyscall emulation

x86/vsyscall_emu/64: Don't use RET in vsyscall emulation

commit c43b9d6d5d712194abe39503253ebef11287fb51 upstream.

This is userspace code and doesn't play by the normal kernel rules.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Borislav Petkov <bp@suse.de>
Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@canonical.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>