linux-kernel - [PATCH 0/2] fs, elf: get rid of MAP

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Date:   Mon, 16 Oct 2017 15:44:44 +0200
From:   Michal Hocko <mhocko@...nel.org>
To:     LKML <linux-kernel@...r.kernel.org>
Cc:     Linus Torvalds <torvalds@...ux-foundation.org>,
        Kees Cook <keescook@...omium.org>,
        Jiri Kosina <jkosina@...e.cz>,
        Al Viro <viro@...iv.linux.org.uk>,
        Oleg Nesterov <oleg@...hat.com>,
        Ingo Molnar <mingo@...hat.com>, Baoquan He <bhe@...hat.com>
Subject: [PATCH 0/2] fs, elf: get rid of MAP_FIXED from the loader

Hi,
the previous discussion didn't really show any hard requirement for
MAP_FIXED usage for the elf segments mapping. I have spent some more
time studying the code (thanks to Qualys for their insight) and
concluded that the current MAP_FIXED usage is rather fragile and not
really needed. The first patch replaces it by a hint mmaping and failing
rather than silently corrupt an existing memory and the second patch
removes MAP_FIXED for the initial segment mapping because this shouldn't
be really needed either, I would even call it wrong.
Anyway, more details are in the changelog of patches. I will really
appreciate any feedback.

This has passed some testing with PIE/PIC binaries running in the loop
without any negative side effects detected.