Re: [PATCH] fs: Preventing READ_IMPLIES_EXEC Propagation

From	Peter Maydell <peter.maydell@linaro.org>
Newsgroups	linux.kernel
Subject	Re: [PATCH] fs: Preventing READ_IMPLIES_EXEC Propagation
Date	2017-04-18 22:10 +0200
Message-ID	<txHBM-22s-17@gated-at.bofh.it> (permalink)
References	<tvMcy-30k-17@gated-at.bofh.it> <tvMcy-30k-15@gated-at.bofh.it> <txENB-le-29@gated-at.bofh.it>
Organization	linux.* mail to news gateway

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On 18 April 2017 at 18:01, Catalin Marinas <catalin.marinas@arm.com> wrote:
> On Thu, Apr 13, 2017 at 08:33:52PM +0800, dongbo (E) wrote:
>> From: Dong Bo <dongbo4@huawei.com>
>>
>> In load_elf_binary(), once the READ_IMPLIES_EXEC flag is set,
>> the flag is propagated to its child processes, even the elf
>> files are marked as not requiring executable stack. It may
>> cause superfluous operations on some arch, e.g.
>> __sync_icache_dcache on aarch64 due to a PROT_READ mmap is
>> also marked as PROT_EXEC.

> That's affecting most architectures with a risk of ABI breakage. We
> could do it on arm64 only, though I'm not yet clear on the ABI
> implications (at a first look, there shouldn't be any).

Is there a reason why it isn't just straightforwardly a bug
(which we could fix) to make READ_IMPLIES_EXEC propagate to
child processes? AFAICT this should be per-process: just because
init happens not to have been (re)compiled to permit non-executable
stacks doesn't mean every process on the system needs to have
an executable stack. Behaviour shouldn't be variable across
architectures either, I would hope.

thanks
-- PMM

Thread

[PATCH] fs: Preventing READ_IMPLIES_EXEC Propagation "dongbo (E)" <dongbo4@huawei.com> - 2017-04-13 14:40 +0200
  Re: [PATCH] fs: Preventing READ_IMPLIES_EXEC Propagation Catalin Marinas <catalin.marinas@arm.com> - 2017-04-18 19:10 +0200
    Re: [PATCH] fs: Preventing READ_IMPLIES_EXEC Propagation Peter Maydell <peter.maydell@linaro.org> - 2017-04-18 22:10 +0200
      Re: [PATCH] fs: Preventing READ_IMPLIES_EXEC Propagation Catalin Marinas <catalin.marinas@arm.com> - 2017-04-19 12:40 +0200
        Re: [PATCH] fs: Preventing READ_IMPLIES_EXEC Propagation Peter Maydell <peter.maydell@linaro.org> - 2017-04-19 12:50 +0200
        Re: [PATCH] fs: Preventing READ_IMPLIES_EXEC Propagation "dongbo (E)" <dongbo4@huawei.com> - 2017-04-20 06:00 +0200
        Re: [PATCH] fs: Preventing READ_IMPLIES_EXEC Propagation Will Deacon <will.deacon@arm.com> - 2017-04-24 17:50 +0200
          Re: [PATCH] fs: Preventing READ_IMPLIES_EXEC Propagation Catalin Marinas <catalin.marinas@arm.com> - 2017-04-24 18:00 +0200
            Re: [PATCH] fs: Preventing READ_IMPLIES_EXEC Propagation Will Deacon <will.deacon@arm.com> - 2017-04-24 18:10 +0200
            Re: [PATCH] fs: Preventing READ_IMPLIES_EXEC Propagation Catalin Marinas <catalin.marinas@arm.com> - 2017-04-24 18:20 +0200

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