x86/ldt: Prevent LDT inheritance on exec()

LDT should not be inherited on exec(), only on fork().

To sanitize that, the LDT initialization for a new process must be split into parts and the actual duplication moved to arch_dup_mmap() which is only called on fork(). This requires that arch_dup_mmap() gains a return value.

Changes vs. V1:
Moved the duplication to arch_dup_mmap() as suggested by Linus.

Thanks,

tglx

---
 arch/powerpc/include/asm/mmu_context.h     |    5 +++--
 arch/x86/kernel/ldt.c                      |   17 +++++------------
 b/arch/um/include/asm/mmu_context.h        |    3 ++-
 b/arch/unicore32/include/asm/mmu_context.h |    5 +++--
 b/arch/x86/include/asm/mmu_context.h       |   24 ++++++++++++++++--------
 include/asm-generic/mm_hooks.h             |    5 +++--
 kernel/fork.c                              |    3 +--
 tools/testing/selftests/x86/ldt_gdt.c      |    9 +++------
 8 files changed, 36 insertions(+), 35 deletions(-)