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Subject: Re: [PATCH v2 1/5] fs: Add support for an O_MAYEXEC flag on
 sys_open()
To:     Florian Weimer <fweimer@redhat.com>,
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Date:   Fri, 6 Sep 2019 18:06:25 +0200
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On 06/09/2019 17:56, Florian Weimer wrote:
> Let's assume I want to add support for this to the glibc dynamic loader,
> while still being able to run on older kernels.
>
> Is it safe to try the open call first, with O_MAYEXEC, and if that fails
> with EINVAL, try again without O_MAYEXEC?

The kernel ignore unknown open(2) flags, so yes, it is safe even for
older kernel to use O_MAYEXEC.

>
> Or do I risk disabling this security feature if I do that?

It is only a security feature if the kernel support it, otherwise it is
a no-op.

>
> Do we need a different way for recognizing kernel support.  (Note that
> we cannot probe paths in /proc for various reasons.)

There is no need to probe for kernel support.

>
> Thanks,
> Florian
>

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