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From: Ingo Molnar <mingo@kernel.org>
To: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
	Steven Rostedt <rostedt@goodmis.org>,
	Arnd Bergmann <arnd@arndb.de>,
	Daniel Micay <danielmicay@gmail.com>,
	Kees Cook <keescook@chromium.org>,
	Dave Hansen <dave.hansen@linux.intel.com>,
	Alexander Popov <alex.popov@linux.com>,
	Kernel Hardening <kernel-hardening@lists.openwall.com>,
	PaX Team <pageexec@freemail.hu>,
	Brad Spengler <spender@grsecurity.net>,
	Andy Lutomirski <luto@kernel.org>,
	Tycho Andersen <tycho@tycho.ws>,
	Laura Abbott <labbott@redhat.com>,
	Mark Rutland <mark.rutland@arm.com>,
	Borislav Petkov <bp@alien8.de>,
	Richard Sandiford <richard.sandiford@arm.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	"H . Peter Anvin" <hpa@zytor.com>,
	Peter Zijlstra <a.p.zijlstra@chello.nl>,
	"Dmitry V . Levin" <ldv@altlinux.org>,
	Emese Revfy <re.emese@gmail.com>,
	Jonathan Corbet <corbet@lwn.net>,
	Andrey Ryabinin <aryabinin@virtuozzo.com>,
	"Kirill A . Shutemov" <kirill.shutemov@linux.intel.com>,
	Thomas Garnier <thgarnie@google.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Alexei Starovoitov <ast@kernel.org>, Josef Bacik <jbacik@fb.com>,
	Masami Hiramatsu <mhiramat@kernel.org>,
	Nicholas Piggin <npiggin@gmail.com>,
	Al Viro <viro@zeniv.linux.org.uk>,
	"David S . Miller" <davem@davemloft.net>,
	Ding Tianhong <dingtianhong@huawei.com>,
	David Woodhouse <dwmw@amazon.co.uk>,
	Josh Poimboeuf <jpoimboe@redhat.com>,
	Dominik Brodowski <linux@dominikbrodowski.net>,
	Juergen Gross <jgross@suse.com>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Dan Williams <dan.j.williams@intel.com>,
	Mathias Krause <minipli@googlemail.com>,
	Vikas Shivappa <vikas.shivappa@linux.intel.com>,
	Kyle Huey <me@kylehuey.com>,
	Dmitry Safonov <dsafonov@virtuozzo.com>,
	Will Deacon <will.deacon@arm.com>, X86 ML <x86@kernel.org>,
	LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH RFC v9 4/7] x86/entry: Erase kernel stack in syscall_trace_enter()
Date: Mon, 12 Mar 2018 10:21:08 +0100	[thread overview]
Message-ID: <20180312092108.d4ajuj7dk2jxgkon@gmail.com> (raw)
In-Reply-To: <CAKv+Gu-N8mZNu5b4X_+dv37R6gLKn-3EdX+xa40t2bB6fgVTZg@mail.gmail.com>


* Ard Biesheuvel <ard.biesheuvel@linaro.org> wrote:

> > Is it possible to implement this "safe automatic variable initialization" language
> > feature via a GCC plugin robustly, while still keeping code generation sane? (i.e.
> > no forced allocation of stack slots, etc.) It should be a superset of
> > CONFIG_GCC_PLUGIN_STRUCTLEAK=y.
> 
> I think that should be feasible, yes.
> 
> It would be worth trying whether the current code can be simplified, though: it 
> currently takes care not to add such an initialization if it can already spot 
> one, but I wonder whether just blindly adding one at the start and letting the 
> compiler optimize it away again is safer.

Absolutely - followed by:

 - a good look at the resulting code generation with a reasonably uptodate GCC

 - a look at the resulting code with older GCCs, to make sure there's no 
   pathological code generation

... because IMHO in the end it is the practical effects that will make (or break) 
any such attempt.

( BTW., initializing all automatic variables might even speed up certain
  optimization passes, FWIIW. )

Thanks,

	Ingo

  reply	other threads:[~2018-03-12  9:21 UTC|newest]

Thread overview: 59+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-03-03 20:00 [PATCH RFC v9 0/7] Introduce the STACKLEAK feature and a test for it Alexander Popov
2018-03-03 20:00 ` [PATCH RFC v9 1/7] gcc-plugins: Clean up the cgraph_create_edge* macros Alexander Popov
2018-03-03 20:00 ` [PATCH RFC v9 2/7] x86/entry: Add STACKLEAK erasing the kernel stack at the end of syscalls Alexander Popov
2018-03-05 16:41   ` Dave Hansen
2018-03-05 19:43     ` Laura Abbott
2018-03-05 19:50       ` Dave Hansen
2018-03-05 20:25       ` Peter Zijlstra
2018-03-05 21:21         ` Alexander Popov
2018-03-05 21:36           ` Kees Cook
2018-03-21 11:04         ` Alexander Popov
2018-03-21 15:33           ` Dave Hansen
2018-03-22 20:56             ` Alexander Popov
2018-03-26 17:32               ` Kees Cook
2018-03-26 17:43                 ` Andy Lutomirski
2018-03-03 20:00 ` [PATCH RFC v9 3/7] gcc-plugins: Add STACKLEAK plugin for tracking the kernel stack Alexander Popov
2018-03-03 20:00 ` [PATCH RFC v9 4/7] x86/entry: Erase kernel stack in syscall_trace_enter() Alexander Popov
2018-03-05 19:40   ` Dave Hansen
2018-03-05 20:06     ` Kees Cook
2018-03-05 20:15       ` Linus Torvalds
2018-03-05 21:02         ` Alexander Popov
2018-03-05 21:02         ` Kees Cook
2018-03-05 21:40           ` Linus Torvalds
2018-03-05 22:07             ` Linus Torvalds
2018-03-06  0:56             ` Kees Cook
2018-03-06  4:30               ` Linus Torvalds
2018-03-06 17:58                 ` Andy Lutomirski
2018-03-06  7:56               ` [OLD PATCH] net: recvmsg: Unconditionally zero struct sockaddr_storage " Ingo Molnar
2018-03-06  8:08           ` Ingo Molnar
2018-03-06 15:16             ` Daniel Micay
2018-03-06 15:28               ` Daniel Micay
2018-03-06 18:56               ` Linus Torvalds
2018-03-06 19:07                 ` Peter Zijlstra
2018-03-06 19:07                 ` Ard Biesheuvel
2018-03-06 19:16                   ` Linus Torvalds
2018-03-06 20:42                     ` Arnd Bergmann
2018-03-06 21:01                       ` Linus Torvalds
2018-03-06 21:21                         ` Arnd Bergmann
2018-03-06 21:29                           ` Linus Torvalds
2018-03-06 22:09                             ` Arnd Bergmann
2018-03-06 22:24                               ` Linus Torvalds
2018-03-06 21:36                         ` Steven Rostedt
2018-03-06 21:41                           ` Linus Torvalds
2018-03-06 21:47                             ` Linus Torvalds
2018-03-06 22:29                               ` Steven Rostedt
2018-03-06 22:41                                 ` Linus Torvalds
2018-03-06 22:52                                   ` Steven Rostedt
2018-03-06 23:09                                     ` Linus Torvalds
2018-03-12  8:22                               ` Ingo Molnar
2018-03-12  9:00                                 ` Ard Biesheuvel
2018-03-12  9:21                                   ` Ingo Molnar [this message]
2018-03-06 21:47                           ` Arnd Bergmann
2018-03-06 22:19                             ` Linus Torvalds
2018-03-05 20:26       ` Peter Zijlstra
2018-03-03 20:00 ` [PATCH RFC v9 5/7] lkdtm: Add a test for STACKLEAK Alexander Popov
2018-03-03 20:00 ` [PATCH RFC v9 6/7] fs/proc: Show STACKLEAK metrics in the /proc file system Alexander Popov
2018-03-03 20:00 ` [PATCH RFC v9 7/7] doc: self-protection: Add information about STACKLEAK feature Alexander Popov
2018-03-05 19:34 ` [PATCH RFC v9 0/7] Introduce the STACKLEAK feature and a test for it Kees Cook
2018-03-05 19:42   ` Dave Hansen
2018-03-05 20:02     ` Kees Cook

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