From: Kees Cook <keescook@chromium.org>
To: Matthew Wilcox <willy@infradead.org>
Cc: Jann Horn <jannh@google.com>,
Ariadne Conill <ariadne@dereferenced.org>,
Michael Kerrisk <mtk.manpages@gmail.com>,
Christian Brauner <brauner@kernel.org>,
Rich Felker <dalias@libc.org>,
Eric Biederman <ebiederm@xmission.com>,
Alexander Viro <viro@zeniv.linux.org.uk>,
linux-fsdevel@vger.kernel.org, stable@vger.kernel.org,
linux-kernel@vger.kernel.org, linux-hardening@vger.kernel.org
Subject: Re: [PATCH] fs/binfmt_elf: Add padding NULL when argc == 0
Date: Wed, 26 Jan 2022 12:13:16 -0800 [thread overview]
Message-ID: <202201261210.E0E7EB83@keescook> (raw)
In-Reply-To: <YfGqLnE9wNieTsAg@casper.infradead.org>
On Wed, Jan 26, 2022 at 08:08:14PM +0000, Matthew Wilcox wrote:
> On Wed, Jan 26, 2022 at 11:58:39AM -0800, Kees Cook wrote:
> > We can't mutate argc; it'll turn at least some userspace into an
> > infinite loop:
> > https://sources.debian.org/src/valgrind/1:3.18.1-1/none/tests/execve.c/?hl=22#L22
>
> How does that become an infinite loop? We obviously wouldn't mutate
> argc in the caller, just the callee.
Oh, sorry, I misread. It's using /bin/true, not argv[0] (another bit of
code I found was using argv[0]). Yeah, {"", NULL} could work.
> Also, there's a version of this where we only mutate argc if we're
> executing a setuid program, which would remove the privilege
> escalation part of things.
True; though I'd like to keep the logic as non-specialized as possible.
I don't like making stuff conditional on privilege boundaries if we can
make it always happen.
--
Kees Cook
next prev parent reply other threads:[~2022-01-26 20:13 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-01-26 17:57 [PATCH] fs/binfmt_elf: Add padding NULL when argc == 0 Kees Cook
2022-01-26 18:07 ` Jann Horn
2022-01-26 18:42 ` Ariadne Conill
2022-01-26 19:50 ` Jann Horn
2022-01-26 19:58 ` Kees Cook
2022-01-26 20:08 ` Matthew Wilcox
2022-01-26 20:13 ` Kees Cook [this message]
2022-01-26 20:31 ` Eric W. Biederman
2022-01-26 19:56 ` Kees Cook
2022-01-26 20:10 ` Ariadne Conill
2022-01-26 20:46 ` Ariadne Conill
2022-01-26 20:52 ` Rich Felker
2022-01-29 7:41 ` [fs/binfmt_elf] 4736b95ed2: kernel-selftests.x86.make_fail kernel test robot
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