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Subject: Re: [PATCH v4 00/14] Provide generic top-down mmap layout functions
From:   Alex Ghiti <alex@ghiti.fr>
To:     Paul Burton <paul.burton@mips.com>
Cc:     Albert Ou <aou@eecs.berkeley.edu>,
        Kees Cook <keescook@chromium.org>,
        Catalin Marinas <catalin.marinas@arm.com>,
        Palmer Dabbelt <palmer@sifive.com>,
        Will Deacon <will.deacon@arm.com>,
        Russell King <linux@armlinux.org.uk>,
        Ralf Baechle <ralf@linux-mips.org>,
        linux-kernel@vger.kernel.org, linux-mm@kvack.org,
        Luis Chamberlain <mcgrof@kernel.org>,
        linux-riscv@lists.infradead.org,
        Alexander Viro <viro@zeniv.linux.org.uk>,
        James Hogan <jhogan@kernel.org>, linux-fsdevel@vger.kernel.org,
        Andrew Morton <akpm@linux-foundation.org>,
        linux-mips@vger.kernel.org, Christoph Hellwig <hch@lst.de>,
        linux-arm-kernel@lists.infradead.org
References: <20190526134746.9315-1-alex@ghiti.fr>
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Message-ID: <c4049021-50fd-32e5-7052-24d58b31e072@ghiti.fr>
Date:   Sun, 30 Jun 2019 11:34:40 -0400
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On 6/13/19 1:29 AM, Alex Ghiti wrote:
> On 5/26/19 9:47 AM, Alexandre Ghiti wrote:
>> 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


>
>>
>> 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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