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Date: Wed, 28 Jan 2015 00:46:05 +0300
From: Pavel Emelyanov <xemul@parallels.com>
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To: Kees Cook <keescook@chromium.org>, Cyrill Gorcunov <gorcunov@gmail.com>
CC: Andrew Morton <akpm@linux-foundation.org>,
        "Kirill A. Shutemov" <kirill@shutemov.name>,
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Subject: Re: [RFC][PATCH v2] procfs: Always expose /proc/<pid>/map_files/
 and make it readable
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>>> Are mount namespaces handled in this output?
>>
>> Could you clarify this moment, i'm not sure i get it.
> 
> I changed how I asked this question in my review of the documentation,
> but it looks like these symlinks aren't "regular" symlinks (that are
> up to the follower to have access to the file system path shown), but
> rather they bypass VFS. As a result, I'm wondering how things like
> mount namespaces might change this behavior: what is shown, the path
> from the perspective of the target, or from the viewer (which may be
> in separate mount namespaces).

These work just like the /proc/$pid/fd/$n links do. When you readlink
on it the d_path() is called which walks up the dentry/vfsmnt tree
until it reaches either current root or the global one. For "another"
mount namespace case it produces the path relative to this namespace's
root.

Thanks,
Pavel