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From: Kees Cook <keescook@chromium.org>
To: "Reshetova, Elena" <elena.reshetova@intel.com>
Cc: Jann Horn <jannh@google.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	the arch/x86 maintainers <x86@kernel.org>,
	Andy Lutomirski <luto@kernel.org>,
	Peter Zijlstra <peterz@infradead.org>,
	Catalin Marinas <catalin.marinas@arm.com>,
	Will Deacon <will@kernel.org>,
	Mark Rutland <mark.rutland@arm.com>,
	Alexander Potapenko <glider@google.com>,
	Ard Biesheuvel <ard.biesheuvel@linaro.org>,
	Kernel Hardening <kernel-hardening@lists.openwall.com>,
	"linux-arm-kernel@lists.infradead.org"
	<linux-arm-kernel@lists.infradead.org>,
	Linux-MM <linux-mm@kvack.org>,
	kernel list <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v2 0/5] Optionally randomize kernel stack offset each syscall
Date: Wed, 25 Mar 2020 13:27:02 -0700	[thread overview]
Message-ID: <202003251322.180F2536E@keescook> (raw)
In-Reply-To: <BL0PR11MB3281D8D615FA521401B8E320E7CE0@BL0PR11MB3281.namprd11.prod.outlook.com>

On Wed, Mar 25, 2020 at 12:15:12PM +0000, Reshetova, Elena wrote:
> > > Also, are you sure that it isn't possible to make the syscall that
> > > leaked its stack pointer never return to userspace (via ptrace or
> > > SIGSTOP or something like that), and therefore never realign its
> > > stack, while keeping some controlled data present on the syscall's
> > > stack?
> 
> How would you reliably detect that a stack pointer has been leaked
> to userspace while it has been in a syscall? Does not seem to be a trivial
> task to me. 

Well, my expectation is that folks using this defense are also using
panic_on_warn sysctl, etc, so attackers don't get a chance to actually
_use_ register values spilled to dmesg.

-- 
Kees Cook

WARNING: multiple messages have this Message-ID (diff)
From: Kees Cook <keescook@chromium.org>
To: "Reshetova, Elena" <elena.reshetova@intel.com>
Cc: Mark Rutland <mark.rutland@arm.com>,
	Ard Biesheuvel <ard.biesheuvel@linaro.org>,
	Jann Horn <jannh@google.com>,
	Peter Zijlstra <peterz@infradead.org>,
	Catalin Marinas <catalin.marinas@arm.com>,
	the arch/x86 maintainers <x86@kernel.org>,
	kernel list <linux-kernel@vger.kernel.org>,
	Linux-MM <linux-mm@kvack.org>,
	Alexander Potapenko <glider@google.com>,
	Andy Lutomirski <luto@kernel.org>,
	Kernel Hardening <kernel-hardening@lists.openwall.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	Will Deacon <will@kernel.org>,
	"linux-arm-kernel@lists.infradead.org"
	<linux-arm-kernel@lists.infradead.org>
Subject: Re: [PATCH v2 0/5] Optionally randomize kernel stack offset each syscall
Date: Wed, 25 Mar 2020 13:27:02 -0700	[thread overview]
Message-ID: <202003251322.180F2536E@keescook> (raw)
In-Reply-To: <BL0PR11MB3281D8D615FA521401B8E320E7CE0@BL0PR11MB3281.namprd11.prod.outlook.com>

On Wed, Mar 25, 2020 at 12:15:12PM +0000, Reshetova, Elena wrote:
> > > Also, are you sure that it isn't possible to make the syscall that
> > > leaked its stack pointer never return to userspace (via ptrace or
> > > SIGSTOP or something like that), and therefore never realign its
> > > stack, while keeping some controlled data present on the syscall's
> > > stack?
> 
> How would you reliably detect that a stack pointer has been leaked
> to userspace while it has been in a syscall? Does not seem to be a trivial
> task to me. 

Well, my expectation is that folks using this defense are also using
panic_on_warn sysctl, etc, so attackers don't get a chance to actually
_use_ register values spilled to dmesg.

-- 
Kees Cook

_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

  reply	other threads:[~2020-03-25 20:27 UTC|newest]

Thread overview: 52+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-03-24 20:32 [PATCH v2 0/5] Optionally randomize kernel stack offset each syscall Kees Cook
2020-03-24 20:32 ` Kees Cook
2020-03-24 20:32 ` [PATCH v2 1/5] jump_label: Provide CONFIG-driven build state defaults Kees Cook
2020-03-24 20:32   ` Kees Cook
2020-03-24 22:06   ` Peter Zijlstra
2020-03-24 22:06     ` Peter Zijlstra
2020-03-24 20:32 ` [PATCH v2 2/5] init_on_alloc: Unpessimize default-on builds Kees Cook
2020-03-24 20:32   ` Kees Cook
2020-03-26 15:48   ` Alexander Potapenko
2020-03-26 15:48     ` Alexander Potapenko
2020-03-24 20:32 ` [PATCH v2 3/5] stack: Optionally randomize kernel stack offset each syscall Kees Cook
2020-03-24 20:32   ` Kees Cook
2020-03-30 11:25   ` Mark Rutland
2020-03-30 11:25     ` Mark Rutland
2020-03-30 18:18     ` Kees Cook
2020-03-30 18:18       ` Kees Cook
2020-03-30 18:27     ` Kees Cook
2020-03-30 18:27       ` Kees Cook
2020-03-24 20:32 ` [PATCH v2 4/5] x86/entry: Enable random_kstack_offset support Kees Cook
2020-03-24 20:32   ` Kees Cook
2020-03-28 22:26   ` Kees Cook
2020-03-28 22:26     ` Kees Cook
2020-03-24 20:32 ` [PATCH v2 5/5] arm64: entry: " Kees Cook
2020-03-24 20:32   ` Kees Cook
2020-03-25 13:21   ` Mark Rutland
2020-03-25 13:21     ` Mark Rutland
2020-03-25 20:22     ` Kees Cook
2020-03-25 20:22       ` Kees Cook
2020-03-26 11:15       ` Mark Rutland
2020-03-26 11:15         ` Mark Rutland
2020-03-26 16:31         ` Kees Cook
2020-03-26 16:31           ` Kees Cook
2020-03-30 11:26           ` Mark Rutland
2020-03-30 11:26             ` Mark Rutland
2020-04-20 20:54   ` Will Deacon
2020-04-20 20:54     ` Will Deacon
2020-04-20 22:34     ` Kees Cook
2020-04-20 22:34       ` Kees Cook
2020-04-21  7:02       ` Will Deacon
2020-04-21  7:02         ` Will Deacon
2020-03-24 21:28 ` [PATCH v2 0/5] Optionally randomize kernel stack offset each syscall Jann Horn
2020-03-24 21:28   ` Jann Horn
2020-03-24 23:07   ` Kees Cook
2020-03-24 23:07     ` Kees Cook
2020-03-25 12:15     ` Reshetova, Elena
2020-03-25 12:15       ` Reshetova, Elena
2020-03-25 20:27       ` Kees Cook [this message]
2020-03-25 20:27         ` Kees Cook
2020-03-25 23:20         ` Jann Horn
2020-03-25 23:20           ` Jann Horn
2020-03-26 17:18           ` Kees Cook
2020-03-26 17:18             ` Kees Cook

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