linux-kernel - Re: [PATCHv4 0/5] Fix compatible mmap() return pointer over 4Gb

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Date:   Mon, 6 Feb 2017 19:46:55 +0300
From:   Dmitry Safonov <dsafonov@...tuozzo.com>
To:     <linux-kernel@...r.kernel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>,
        Andy Lutomirski <luto@...nel.org>, Borislav Petkov <bp@...e.de>
CC:     <0x7f454c46@...il.com>, <x86@...nel.org>, <linux-mm@...ck.org>,
        Shuah Khan <shuah@...nel.org>,
        <linux-kselftest@...r.kernel.org>
Subject: Re: [PATCHv4 0/5] Fix compatible mmap() return pointer over 4Gb

On 01/30/2017 03:04 PM, Dmitry Safonov wrote:
> 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.

Gentle ping. Any thought on this?

>
> [1]: https://marc.info/?l=linux-kernel&m=148311451525315
> [2]: https://marc.info/?l=linux-kernel&m=148415888707662
>
> Cc: Thomas Gleixner <tglx@...utronix.de>
> Cc: Ingo Molnar <mingo@...hat.com>
> Cc: "H. Peter Anvin" <hpa@...or.com>
> Cc: Andy Lutomirski <luto@...nel.org>
> Cc: Borislav Petkov <bp@...e.de>
> Cc: x86@...nel.org
> Cc: linux-mm@...ck.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
>


-- 
              Dmitry