From: Florian Weimer <fweimer@redhat.com>
To: Andy Lutomirski <luto@kernel.org>
Cc: linux-arch@vger.kernel.org,
Linux API <linux-api@vger.kernel.org>,
linux-x86_64@vger.kernel.org,
kernel-hardening@lists.openwall.com, linux-mm@kvack.org,
the arch/x86 maintainers <x86@kernel.org>,
musl@lists.openwall.com, libc-alpha@sourceware.org,
linux-kernel@vger.kernel.org,
Dave Hansen <dave.hansen@intel.com>,
Kees Cook <keescook@chromium.org>,
Andrei Vagin <avagin@gmail.com>
Subject: [musl] Re: [PATCH v3 1/3] x86: Implement arch_prctl(ARCH_VSYSCALL_CONTROL) to disable vsyscall
Date: Fri, 14 Jan 2022 14:36:24 +0100 [thread overview]
Message-ID: <87sftqtp5z.fsf@oldenburg.str.redhat.com> (raw)
In-Reply-To: <e431fa42-26ec-8ac6-f954-e681b1e0e9a6@kernel.org> (Andy Lutomirski's message of "Thu, 13 Jan 2022 13:47:26 -0800")
* Andy Lutomirski:
> Is there a reason you didn't just change the check earlier in the
> function to:
>
> if (vsyscall_mode == NONE || current->mm->context.vsyscall_disabled)
Andrei requested that I don't print anything if vsyscall was disabled.
The original patch used a different message for better diagnostics.
> Also, I still think the prctl should not be available if
> vsyscall=emulate. Either we should fully implement it or we should
> not implement. We could even do:
>
> pr_warn_once("userspace vsyscall hardening request ignored because you
> have vsyscall=emulate. Unless you absolutely need vsyscall=emulate,
> update your system to use vsyscall=xonly.\n");
>
> and thus encourage good behavior.
I think there is still some hardening applied even with
vsyscall=emulate. The question is what is more important: the
additional hardening, or clean, easily described behavior of the
interface.
Maybe ARCH_VSYSCALL_CONTROL could return different values based on to
what degree it could disable vsyscall?
The pr_warn_once does not seem particularly useful. Anyone who upgrades
glibc and still uses vsyscall=emulate will see that, with no way to
disable it.
Thanks,
Florian
prev parent reply other threads:[~2022-01-14 13:36 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-01-05 16:02 [musl] " Florian Weimer
2022-01-05 16:03 ` [musl] [PATCH v3 2/3] selftests/x86/Makefile: Support per-target $(LIBS) configuration Florian Weimer
2022-01-05 16:03 ` [musl] [PATCH v3 3/3] x86: Add test for arch_prctl(ARCH_VSYSCALL_CONTROL) Florian Weimer
2022-01-13 21:31 ` [musl] " Andy Lutomirski
2022-01-13 21:57 ` Florian Weimer
2022-01-13 21:31 ` [musl] Re: [PATCH v3 2/3] selftests/x86/Makefile: Support per-target $(LIBS) configuration Andy Lutomirski
2022-01-13 22:00 ` Florian Weimer
2022-01-14 2:34 ` Andy Lutomirski
2022-01-14 13:28 ` Florian Weimer
2022-01-13 17:27 ` [musl] Re: [PATCH v3 1/3] x86: Implement arch_prctl(ARCH_VSYSCALL_CONTROL) to disable vsyscall Florian Weimer
2022-01-13 21:47 ` Andy Lutomirski
2022-01-14 13:36 ` Florian Weimer [this message]
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