Re: [PATCHv2 0/5] Fix compatible mmap() return pointer over 4Gb

[Andy Lutomirski]

Kirill, can you take a careful look at this series?  I bet you're
going to run into this stuff too.

On Mon, Jan 16, 2017 at 4:33 AM, Dmitry Safonov <dsafonov@xxxxxxxxxxxxx> wrote:
> 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@xxxxxxxxxxxxx>
> Cc: Ingo Molnar <mingo@xxxxxxxxxx>
> Cc: "H. Peter Anvin" <hpa@xxxxxxxxx>
> Cc: Andy Lutomirski <luto@xxxxxxxxxx>
> Cc: Borislav Petkov <bp@xxxxxxx>
> Cc: x86@xxxxxxxxxx
> Cc: linux-mm@xxxxxxxxx
>
> Dmitry Safonov (5):
>   x86/mm: split arch_mmap_rnd() on compat/native versions
>   x86/mm: introduce mmap_{,legacy}_base
>   x86/mm: fix native mmap() in compat bins and vice-versa
>   x86/mm: for MAP_32BIT check in_compat_syscall() instead TIF_ADDR32
>   selftests/x86: add test to check compat mmap() return addr
>
>  arch/x86/include/asm/elf.h                     |  14 +-
>  arch/x86/include/asm/processor.h               |   2 +-
>  arch/x86/kernel/sys_x86_64.c                   |  48 +++++-
>  arch/x86/mm/hugetlbpage.c                      |   2 +-
>  arch/x86/mm/mmap.c                             |  56 ++++---
>  tools/testing/selftests/x86/Makefile           |   2 +-
>  tools/testing/selftests/x86/test_compat_mmap.c | 208 +++++++++++++++++++++++++
>  7 files changed, 301 insertions(+), 31 deletions(-)
>  create mode 100644 tools/testing/selftests/x86/test_compat_mmap.c
>
> --
> 2.11.0
>