On 6/13/19 1:29 AM, Alex Ghiti wrote:

On 5/26/19 9:47 AM, Alexandre Ghiti wrote:

quoted

This series introduces generic functions to make top-down mmap layout
easily accessible to architectures, in particular riscv which was
the initial goal of this series.
The generic implementation was taken from arm64 and used successively
by arm, mips and finally riscv.

Note that in addition the series fixes 2 issues:
- stack randomization was taken into account even if not necessary.
- [1] fixed an issue with mmap base which did not take into account
   randomization but did not report it to arm and mips, so by moving
   arm64 into a generic library, this problem is now fixed for both
   architectures.

This work is an effort to factorize architecture functions to avoid
code duplication and oversights as in [1].

[1]: 
https://www.mail-archive.com/linux-kernel@vger.kernel.org/msg1429066.html

Changes in v4:
   - Make ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT select 
ARCH_HAS_ELF_RANDOMIZE
     by default as suggested by Kees,
   - ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT depends on MMU and defines 
the
     functions needed by ARCH_HAS_ELF_RANDOMIZE => architectures that 
use
     the generic mmap topdown functions cannot have 
ARCH_HAS_ELF_RANDOMIZE
     selected without MMU, but I think it's ok since randomization 
without
     MMU does not add much security anyway.
   - There is no common API to determine if a process is 32b, so I 
came up with
     !IS_ENABLED(CONFIG_64BIT) || is_compat_task() in [PATCH v4 12/14].
   - Mention in the change log that x86 already takes care of not 
offseting mmap
     base address if the task does not want randomization.
   - Re-introduce a comment that should not have been removed.
   - Add Reviewed/Acked-By from Paul, Christoph and Kees, thank you 
for that.
   - I tried to minimize the changes from the commits in v3 in order 
to make
     easier the review of the v4, the commits changed or added are:
     - [PATCH v4 5/14]
     - [PATCH v4 8/14]
     - [PATCH v4 11/14]
     - [PATCH v4 12/14]
     - [PATCH v4 13/14]

Hi Paul,

Compared to the previous version you already acked, patches 11, 12 and 13
would need your feedback, do you have time to take a look at them ?

Hope I don't bother you,

Thanks,

Alex

Hi Paul,

Would you have time to give your feedback on patches 11, 12 and 13 ?

Thanks,

Alex

quoted

Changes in v3:
   - Split into small patches to ease review as suggested by Christoph
     Hellwig and Kees Cook
   - Move help text of new config as a comment, as suggested by 
Christoph
   - Make new config depend on MMU, as suggested by Christoph

Changes in v2 as suggested by Christoph Hellwig:
   - Preparatory patch that moves randomize_stack_top
   - Fix duplicate config in riscv
   - Align #if defined on next line => this gives rise to a checkpatch
     warning. I found this pattern all around the tree, in the same 
proportion
     as the previous pattern which was less pretty:
     git grep -C 1 -n -P "^#if defined.+\|\|.*\\\\$"

Alexandre Ghiti (14):
   mm, fs: Move randomize_stack_top from fs to mm
   arm64: Make use of is_compat_task instead of hardcoding this test
   arm64: Consider stack randomization for mmap base only when necessary
   arm64, mm: Move generic mmap layout functions to mm
   arm64, mm: Make randomization selected by generic topdown mmap layout
   arm: Properly account for stack randomization and stack guard gap
   arm: Use STACK_TOP when computing mmap base address
   arm: Use generic mmap top-down layout and brk randomization
   mips: Properly account for stack randomization and stack guard gap
   mips: Use STACK_TOP when computing mmap base address
   mips: Adjust brk randomization offset to fit generic version
   mips: Replace arch specific way to determine 32bit task with generic
     version
   mips: Use generic mmap top-down layout and brk randomization
   riscv: Make mmap allocation top-down by default

  arch/Kconfig                       |  11 +++
  arch/arm/Kconfig                   |   2 +-
  arch/arm/include/asm/processor.h   |   2 -
  arch/arm/kernel/process.c          |   5 --
  arch/arm/mm/mmap.c                 |  52 --------------
  arch/arm64/Kconfig                 |   2 +-
  arch/arm64/include/asm/processor.h |   2 -
  arch/arm64/kernel/process.c        |   8 ---
  arch/arm64/mm/mmap.c               |  72 -------------------
  arch/mips/Kconfig                  |   2 +-
  arch/mips/include/asm/processor.h  |   5 --
  arch/mips/mm/mmap.c                |  84 ----------------------
  arch/riscv/Kconfig                 |  11 +++
  fs/binfmt_elf.c                    |  20 ------
  include/linux/mm.h                 |   2 +
  kernel/sysctl.c                    |   6 +-
  mm/util.c                          | 107 ++++++++++++++++++++++++++++-
  17 files changed, 137 insertions(+), 256 deletions(-)

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