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From: Ingo Molnar <mingo@kernel.org>
To: Russell King - ARM Linux <linux@arm.linux.org.uk>
Cc: Kees Cook <keescook@chromium.org>,
	Heiko Carstens <heiko.carstens@de.ibm.com>,
	Michael Ellerman <mpe@ellerman.id.au>,
	"James E.J. Bottomley" <jejb@parisc-linux.org>,
	Catalin Marinas <catalin.marinas@arm.com>,
	LKML <linux-kernel@vger.kernel.org>,
	Andy Lutomirski <luto@amacapital.net>,
	"H. Peter Anvin" <hpa@zytor.com>,
	Mathias Krause <minipli@googlemail.com>,
	Ingo Molnar <mingo@redhat.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	"x86@kernel.org" <x86@kernel.org>, Arnd Bergmann <arnd@arndb.de>,
	PaX Team <pageexec@freemail.hu>, Emese Revfy <re.emese@gmail.com>,
	"kernel-hardening@lists.openwall.com" 
	<kernel-hardening@lists.openwall.com>,
	linux-arch <linux-arch@vger.kernel.org>
Subject: Re: [PATCH v2 1/4] init: create cmdline param to disable readonly
Date: Tue, 1 Dec 2015 08:24:03 +0100	[thread overview]
Message-ID: <20151201072403.GA28270@gmail.com> (raw)
In-Reply-To: <20151130222437.GT8644@n2100.arm.linux.org.uk>


* Russell King - ARM Linux <linux@arm.linux.org.uk> wrote:

> On Mon, Nov 30, 2015 at 01:52:10PM -0800, Kees Cook wrote:
> > On Wed, Nov 25, 2015 at 11:51 PM, Ingo Molnar <mingo@kernel.org> wrote:
> > > * Kees Cook <keescook@chromium.org> wrote:
> > >> +#ifdef CONFIG_DEBUG_RODATA
> > >
> > > Btw., could you please remove the Kconfig option altogether in an additional patch
> > > and make read-only sections an always-on feature? It has been default-y for years
> > > and all distros have it enabled.
> > 
> > Yeah, this is something I've wanted to do for a while, but I would
> > point out that only a few architectures have actually implemented it,
> > and for arm and arm64 it was very recent:
> 
> I don't think it can entirely be a kernel command line option.  On ARM,
> enabling DEBUG_RODATA has a substantial effect on the size of the kernel
> image - we have to pad various sections to 1MB boundaries so we can
> set the appropriate permissions.
> 
> Forcing this layout on everyone won't work.

Yeah, so I'd suggest to have it always-on on x86 (after adding the boot option), 
to simplify the x86 code and to make it more obvious that we rely on this.

There's a moderate amount of #ifdeffery around this:

  triton:~/tip> git grep -w CONFIG_DEBUG_RODATA arch/x86/  | grep \# | wc -l
  15

Thanks,

	Ingo

WARNING: multiple messages have this Message-ID (diff)
From: Ingo Molnar <mingo@kernel.org>
To: Russell King - ARM Linux <linux@arm.linux.org.uk>
Cc: Kees Cook <keescook@chromium.org>,
	Heiko Carstens <heiko.carstens@de.ibm.com>,
	Michael Ellerman <mpe@ellerman.id.au>,
	"James E.J. Bottomley" <jejb@parisc-linux.org>,
	Catalin Marinas <catalin.marinas@arm.com>,
	LKML <linux-kernel@vger.kernel.org>,
	Andy Lutomirski <luto@amacapital.net>,
	"H. Peter Anvin" <hpa@zytor.com>,
	Mathias Krause <minipli@googlemail.com>,
	Ingo Molnar <mingo@redhat.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	"x86@kernel.org" <x86@kernel.org>, Arnd Bergmann <arnd@arndb.de>,
	PaX Team <pageexec@freemail.hu>, Emese Revfy <re.emese@gmail.com>,
	"kernel-hardening@lists.openwall.com"
	<kernel-hardening@lists.openwall.com>,
	linux-arch <linux-arch@vger.kernel.org>
Subject: [kernel-hardening] Re: [PATCH v2 1/4] init: create cmdline param to disable readonly
Date: Tue, 1 Dec 2015 08:24:03 +0100	[thread overview]
Message-ID: <20151201072403.GA28270@gmail.com> (raw)
In-Reply-To: <20151130222437.GT8644@n2100.arm.linux.org.uk>


* Russell King - ARM Linux <linux@arm.linux.org.uk> wrote:

> On Mon, Nov 30, 2015 at 01:52:10PM -0800, Kees Cook wrote:
> > On Wed, Nov 25, 2015 at 11:51 PM, Ingo Molnar <mingo@kernel.org> wrote:
> > > * Kees Cook <keescook@chromium.org> wrote:
> > >> +#ifdef CONFIG_DEBUG_RODATA
> > >
> > > Btw., could you please remove the Kconfig option altogether in an additional patch
> > > and make read-only sections an always-on feature? It has been default-y for years
> > > and all distros have it enabled.
> > 
> > Yeah, this is something I've wanted to do for a while, but I would
> > point out that only a few architectures have actually implemented it,
> > and for arm and arm64 it was very recent:
> 
> I don't think it can entirely be a kernel command line option.  On ARM,
> enabling DEBUG_RODATA has a substantial effect on the size of the kernel
> image - we have to pad various sections to 1MB boundaries so we can
> set the appropriate permissions.
> 
> Forcing this layout on everyone won't work.

Yeah, so I'd suggest to have it always-on on x86 (after adding the boot option), 
to simplify the x86 code and to make it more obvious that we rely on this.

There's a moderate amount of #ifdeffery around this:

  triton:~/tip> git grep -w CONFIG_DEBUG_RODATA arch/x86/  | grep \# | wc -l
  15

Thanks,

	Ingo

  parent reply	other threads:[~2015-12-01  7:24 UTC|newest]

Thread overview: 42+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-11-25 23:31 [PATCH v2 0/4] introduce post-init read-only memory Kees Cook
2015-11-25 23:31 ` [kernel-hardening] " Kees Cook
2015-11-25 23:31 ` [PATCH v2 1/4] init: create cmdline param to disable readonly Kees Cook
2015-11-25 23:31   ` [kernel-hardening] " Kees Cook
2015-11-26  0:37   ` PaX Team
2015-11-26  0:37     ` [kernel-hardening] " PaX Team
2015-11-26  0:37     ` PaX Team
2015-11-26  0:37     ` PaX Team
2015-11-26  0:44   ` [kernel-hardening] " Greg KH
2015-11-26  0:44     ` Greg KH
2015-11-26  7:51   ` Ingo Molnar
2015-11-26  7:51     ` [kernel-hardening] " Ingo Molnar
2015-11-30 21:52     ` Kees Cook
2015-11-30 21:52       ` [kernel-hardening] " Kees Cook
2015-11-30 21:52       ` Kees Cook
2015-11-30 22:24       ` Russell King - ARM Linux
2015-11-30 22:24         ` [kernel-hardening] " Russell King - ARM Linux
2015-11-30 22:24         ` Russell King - ARM Linux
2015-11-30 22:34         ` Kees Cook
2015-11-30 22:34           ` [kernel-hardening] " Kees Cook
2015-11-30 22:34           ` Kees Cook
2015-12-01  7:24         ` Ingo Molnar [this message]
2015-12-01  7:24           ` [kernel-hardening] " Ingo Molnar
2015-12-01  7:24           ` Ingo Molnar
2015-12-01  7:19       ` Heiko Carstens
2015-12-01  7:19         ` [kernel-hardening] " Heiko Carstens
2015-12-01  7:19         ` Heiko Carstens
2015-11-25 23:31 ` [PATCH v2 2/4] introduce post-init read-only memory Kees Cook
2015-11-25 23:31   ` [kernel-hardening] " Kees Cook
2015-11-26  0:15   ` PaX Team
2015-11-26  0:15     ` [kernel-hardening] " PaX Team
2015-11-26  0:15     ` PaX Team
2015-11-26  0:15     ` PaX Team
2015-11-30 22:24     ` H. Peter Anvin
2015-11-30 22:24       ` [kernel-hardening] " H. Peter Anvin
2015-12-09 19:35       ` Kees Cook
2015-12-09 19:35         ` [kernel-hardening] " Kees Cook
2015-12-09 19:35         ` Kees Cook
2015-11-25 23:31 ` [PATCH v2 3/4] lkdtm: verify that __ro_after_init works correctly Kees Cook
2015-11-25 23:31   ` [kernel-hardening] " Kees Cook
2015-11-25 23:31 ` [PATCH v2 4/4] x86, vdso: mark vDSO read-only after init Kees Cook
2015-11-25 23:31   ` [kernel-hardening] " Kees Cook

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