linux-kernel - Re: Suggested Patch is not working for 22851 Bugzilla issue

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Date:   Tue, 19 Nov 2019 10:57:08 +0100
From:   Michal Hocko <mhocko@...nel.org>
To:     Bala S <balas2380@...il.com>
Cc:     linux-kernel@...r.kernel.org, linux-api@...r.kernel.org,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Kees Cook <keescook@...omium.org>
Subject: Re: Suggested Patch is not working for 22851 Bugzilla issue

Hi
let me add Kees Cook and Linus to the cc list. I didn't have much
time to study the bug report and cannot really comment on the security
aspect of it. But let me point out that a big part of
MAP_FIXED_NOREPLACE usage has been removed from the loader code just
recently because it has caused some regressions
http://lkml.kernel.org/r/20191005233227.GB25745@shell.armlinux.org.uk
b212921b13bd ("elf: don't use MAP_FIXED_NOREPLACE for elf executable mappings").
So you definitely want to look at the current Linus tree for your future
experiments.

On Tue 19-11-19 10:37:44, Bala S wrote:
> Hi Mhocko,
> 
> https://sourceware.org/bugzilla/show_bug.cgi?id=22851
> For the above issue, I have found the patch.
> 
> Patch link:
> https://www.mail-archive.com/linux-kernel@vger.kernel.org/msg1561935.html
> 
> Only change i noticed is 'MAP_FIXED_NOREPLACE' is used instead of
> 'MAP_FIXED_SAFE'.
> 
> I ran test case on the following targets with this patch:
> 
> 1. For X86-64, Still i could see the reported issue( 'libevil.so' just
> runs ‘cat /etc/passwd')
> 
> 2. For MIPS-64, i am not seeing the malicious file content as
> reported. But ‘ldd’ could not found ‘libevil.so’.
> 
> root@...umips64:~/LIN1019-1806# ldd ./main
>         linux-vdso.so.1 (0x000000fff1f20000)
>         libevil.so => not found
>         libc.so.6 => /lib/libc.so.6 (0x0000005e46f70000)
>         /lib/ld.so.1 (0x000000fff7888000)
> 
> I am not clear why this patch is not working for X86-64? But it is
> working for MIPS-64 with some issue.
> Please let me know, if anything is pending on this patch for the reported issue.
> 
> Thanks,
> Bala

-- 
Michal Hocko
SUSE Labs