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From: Christian Brauner <christian.brauner@ubuntu.com>
To: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Andreas Schwab <schwab@linux-m68k.org>,
	Jann Horn <jannh@google.com>, Kees Cook <keescook@chromium.org>,
	Al Viro <viro@zeniv.linux.org.uk>,
	Andrew Morton <akpm@linux-foundation.org>,
	Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>,
	Eric Biggers <ebiggers3@gmail.com>,
	Dmitry Vyukov <dvyukov@google.com>,
	linux-fsdevel <linux-fsdevel@vger.kernel.org>,
	linux-security-module <linux-security-module@vger.kernel.org>,
	Linux API <linux-api@vger.kernel.org>,
	kernel list <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 1/4] exec: Change uselib(2) IS_SREG() failure to EACCES
Date: Tue, 19 May 2020 15:29:31 +0200	[thread overview]
Message-ID: <20200519132931.3b7yugfv2ajry6y7@wittgenstein> (raw)
In-Reply-To: <87ftbwun0h.fsf@x220.int.ebiederm.org>

On Tue, May 19, 2020 at 07:28:46AM -0500, Eric W. Biederman wrote:
> Andreas Schwab <schwab@linux-m68k.org> writes:
> 
> > On Mai 19 2020, Eric W. Biederman wrote:
> >
> >> I am wondering if there are source trees for libc4 or libc5 around
> >> anywhere that we can look at to see how usage of uselib evolved.
> >
> > libc5 is available from archive.debian.org.
> >
> > http://archive.debian.org/debian-archive/debian/pool/main/libc/libc/libc_5.4.46.orig.tar.gz
> 
> Interesting.
> 
> It appears that the old a.out code to make use of uselib remained in
> the libc5 sources but it was all conditional on the being compiled not
> to use ELF.
> 
> libc5 did provide a wrapper for the uselib system call.
> 
> It appears glibc also provides a wrapper for the uselib system call
> named: uselib@GLIBC_2.2.5.
> 
> I don't see a glibc header file that provides a declaration for uselib
> though.
> 
> So the question becomes did anyone use those glibc wrappers.

The only software I could find was ski, the ia64 instruction set
emulator, which apparently used to make use of this and when glibc
removed they did:

#define uselib(libname) syscall(__NR_uselib, libname)

but they only define it for the sake of the internal syscall list they
maintain so not actively using it. I just checked, ski is available on
Fedora 31 and Fedora has USELIB disabled.
Codesearch on Debian yields no users that actively use the syscall for
anything.

Christian

  reply	other threads:[~2020-05-19 13:29 UTC|newest]

Thread overview: 28+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-05-18  5:54 [PATCH 0/4] Relocate execve() sanity checks Kees Cook
2020-05-18  5:54 ` [PATCH 1/4] exec: Change uselib(2) IS_SREG() failure to EACCES Kees Cook
2020-05-18 13:02   ` Christian Brauner
2020-05-18 14:43     ` Jann Horn
2020-05-18 14:46       ` Christian Brauner
2020-05-18 23:57         ` Eric W. Biederman
2020-05-19  8:11           ` Christian Brauner
2020-05-19  8:37           ` Andreas Schwab
2020-05-19 11:56             ` Eric W. Biederman
2020-05-19 12:12               ` Andreas Schwab
2020-05-19 12:28                 ` Eric W. Biederman
2020-05-19 13:29                   ` Christian Brauner [this message]
2020-05-19 14:49                     ` Eric W. Biederman
2020-05-19 13:13               ` Christian Brauner
2020-05-19 14:32                 ` Geert Uytterhoeven
2020-05-19 14:47                   ` Christian Brauner
2020-05-18  5:54 ` [PATCH 2/4] exec: Relocate S_ISREG() check Kees Cook
     [not found]   ` <20200525091420.GI12456@shao2-debian>
2020-06-04 22:45     ` [exec] 166d03c9ec: ltp.execveat02.fail Kees Cook
2020-06-05  2:57     ` Kees Cook
2020-05-18  5:54 ` [PATCH 3/4] exec: Relocate path_noexec() check Kees Cook
2020-05-18  5:54 ` [PATCH 4/4] fs: Include FMODE_EXEC when converting flags to f_mode Kees Cook
2020-05-19 15:06 ` [PATCH 0/4] Relocate execve() sanity checks Eric W. Biederman
2020-05-19 16:26   ` Kees Cook
2020-05-19 17:41     ` Eric W. Biederman
2020-05-19 17:56       ` Kees Cook
2020-05-19 18:42         ` Eric W. Biederman
2020-05-19 21:17           ` Kees Cook
2020-05-19 22:58             ` John Johansen

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