linux-kernel - Re: [PATCH 1/4] exec: Change uselib(2) IS

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Message-ID: <20200519131341.qiysndpmj75zfjtz@wittgenstein>
Date:   Tue, 19 May 2020 15:13:41 +0200
From:   Christian Brauner <christian.brauner@...ntu.com>
To:     "Eric W. Biederman" <ebiederm@...ssion.com>
Cc:     Andreas Schwab <schwab@...ux-m68k.org>,
        Jann Horn <jannh@...gle.com>,
        Kees Cook <keescook@...omium.org>,
        Al Viro <viro@...iv.linux.org.uk>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>,
        Eric Biggers <ebiggers3@...il.com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        linux-fsdevel <linux-fsdevel@...r.kernel.org>,
        linux-security-module <linux-security-module@...r.kernel.org>,
        Linux API <linux-api@...r.kernel.org>,
        kernel list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/4] exec: Change uselib(2) IS_SREG() failure to EACCES

On Tue, May 19, 2020 at 06:56:36AM -0500, Eric W. Biederman wrote:
> Andreas Schwab <schwab@...ux-m68k.org> writes:
> 
> > On Mai 18 2020, Eric W. Biederman wrote:
> >
> >> If it was only libc4 and libc5 that used the uselib system call then it
> >> can probably be removed after enough time.
> >
> > Only libc4 used it, libc5 was already ELF.
> 
> binfmt_elf.c supports uselib.  In a very a.out ish way.  Do you know if
> that support was ever used?
> 
> If we are truly talking a.out only we should be able to make uselib
> conditional on a.out support in the kernel which is strongly mostly
> disabled at this point.

The only ones that even allow setting AOUT:

arch/alpha/Kconfig:     select HAVE_AOUT
arch/m68k/Kconfig:      select HAVE_AOUT if MMU

and x86 deprecated it March 2019:
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=eac616557050737a8d6ef6fe0322d0980ff0ffde

Christian