[PATCHv4 0/5] Fix compatible mmap() return pointer over 4Gb

[Dmitry Safonov <dsafonov@virtuozzo.com>]

Changes since v3:
- fixed usage of 64-bit random mask for 32-bit mm->mmap_compat_base,
  during introducing mmap_compat{_legacy,}_base

Changes since v2:
- don't distinguish native and compat tasks by TIF_ADDR32,
  introduced mmap_compat{_legacy,}_base which allows to treat them
  the same
- fixed kbuild errors

Changes since v1:
- Recalculate mmap_base instead of using max possible virtual address
  for compat/native syscall. That will make policy for allocation the
  same in 32-bit binaries and in 32-bit syscalls in 64-bit binaries.
  I need this because sys_mmap() in restored 32-bit process shouldn't
  hit the stack area.
- Fixed mmap() with MAP_32BIT flag in the same usecases
- used in_compat_syscall() helper rather TS_COMPAT check (Andy noticed)
- introduced find_top() helper as suggested by Andy to simplify code
- fixed test error-handeling: it checked the result of sys_mmap() with
  MMAP_FAILED, which is not correct, as it calls raw syscall - now
  checks return value to be aligned to PAGE_SIZE.

Description from v1 [2]:

A fix for bug in mmap() that I referenced in [1].
Also selftest for it.

I would like to mark the fix as for stable v4.9 kernel if it'll
be accepted, as I try to support compatible 32-bit C/R
after v4.9 and working compatible mmap() is really wanted there.

[1]: https://marc.info/?l=linux-kernel&m=148311451525315
[2]: https://marc.info/?l=linux-kernel&m=148415888707662

Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@suse.de>
Cc: x86@kernel.org
Cc: linux-mm@kvack.org

Dmitry Safonov (5):
  x86/mm: split arch_mmap_rnd() on compat/native versions
  x86/mm: introduce mmap{,_legacy}_base
  x86/mm: fix 32-bit mmap() for 64-bit ELF
  x86/mm: check in_compat_syscall() instead TIF_ADDR32 for
    mmap(MAP_32BIT)
  selftests/x86: add test to check compat mmap() return addr

 arch/Kconfig                                   |   7 +
 arch/x86/Kconfig                               |   1 +
 arch/x86/include/asm/elf.h                     |   4 +-
 arch/x86/include/asm/processor.h               |   3 +-
 arch/x86/kernel/sys_x86_64.c                   |  32 +++-
 arch/x86/mm/mmap.c                             |  89 +++++++----
 include/linux/mm_types.h                       |   5 +
 tools/testing/selftests/x86/Makefile           |   2 +-
 tools/testing/selftests/x86/test_compat_mmap.c | 208 +++++++++++++++++++++++++
 9 files changed, 311 insertions(+), 40 deletions(-)
 create mode 100644 tools/testing/selftests/x86/test_compat_mmap.c

-- 
2.11.0

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