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Re: [PATCH 1/1] stackleak: Register the 'stackleak_cleanup' pass before the 'mach' pass
- From: Kees Cook <keescook at chromium dot org>
- To: Alexander Popov <alex dot popov at linux dot com>
- Cc: Kernel Hardening <kernel-hardening at lists dot openwall dot com>, Jann Horn <jannh at google dot com>, Andy Lutomirski <luto at kernel dot org>, Borislav Petkov <bp at alien8 dot de>, Thomas Gleixner <tglx at linutronix dot de>, Dave Hansen <dave dot hansen at linux dot intel dot com>, Steven Rostedt <rostedt at goodmis dot org>, Peter Zijlstra <peterz at infradead dot org>, Masami Hiramatsu <mhiramat at kernel dot org>, Florian Weimer <fweimer at redhat dot com>, Richard Sandiford <richard dot sandiford at arm dot com>, Segher Boessenkool <segher at kernel dot crashing dot org>, amonakov at ispras dot ru, Tycho Andersen <tycho at tycho dot ws>, Laura Abbott <labbott at redhat dot com>, Mark Rutland <mark dot rutland at arm dot com>, Emese Revfy <re dot emese at gmail dot com>, Thomas Garnier <thgarnie at google dot com>, Ingo Molnar <mingo at kernel dot org>, Will Deacon <will dot deacon at arm dot com>, Alexei Starovoitov <ast at kernel dot org>, Ard Biesheuvel <ard dot biesheuvel at linaro dot org>, "H. Peter Anvin" <hpa at zytor dot com>, "David S. Miller" <davem at davemloft dot net>, linux-arm-kernel <linux-arm-kernel at lists dot infradead dot org>, gcc at gcc dot gnu dot org, LKML <linux-kernel at vger dot kernel dot org>
- Date: Fri, 30 Nov 2018 09:09:02 -0800
- Subject: Re: [PATCH 1/1] stackleak: Register the 'stackleak_cleanup' pass before the 'mach' pass
- References: <1543583987-27948-1-git-send-email-alex.popov@linux.com>
On Fri, Nov 30, 2018 at 5:20 AM Alexander Popov <alex.popov@linux.com> wrote:
>
> Currently the 'stackleak_cleanup' pass deleting a CALL insn is executed
> after the 'reload' pass. That allows gcc to do some weird optimization in
> function prologues and epilogues, which are generated later [1].
>
> Let's avoid that by registering the 'stackleak_cleanup' pass before
> the 'mach' pass, which performs the machine dependent code transformations.
> It's the moment when the stack frame size is final and function prologues
> and epilogues are already generated.
>
> [1] https://www.openwall.com/lists/kernel-hardening/2018/11/23/2
>
> Reported-by: kbuild test robot <lkp@intel.com>
> Signed-off-by: Alexander Popov <alex.popov@linux.com>
Thanks, applied!
-Kees
> ---
> scripts/gcc-plugins/stackleak_plugin.c | 8 +++++---
> 1 file changed, 5 insertions(+), 3 deletions(-)
>
> diff --git a/scripts/gcc-plugins/stackleak_plugin.c b/scripts/gcc-plugins/stackleak_plugin.c
> index 2f48da9..6f41b32 100644
> --- a/scripts/gcc-plugins/stackleak_plugin.c
> +++ b/scripts/gcc-plugins/stackleak_plugin.c
> @@ -363,10 +363,12 @@ __visible int plugin_init(struct plugin_name_args *plugin_info,
> PASS_POS_INSERT_BEFORE);
>
> /*
> - * The stackleak_cleanup pass should be executed after the
> - * "reload" pass, when the stack frame size is final.
> + * The stackleak_cleanup pass should be executed before the "mach"
> + * pass, which performs the machine dependent code transformations.
> + * It's the moment when the stack frame size is already final and
> + * function prologues and epilogues are generated.
> */
> - PASS_INFO(stackleak_cleanup, "reload", 1, PASS_POS_INSERT_AFTER);
> + PASS_INFO(stackleak_cleanup, "mach", 1, PASS_POS_INSERT_BEFORE);
>
> if (!plugin_default_version_check(version, &gcc_version)) {
> error(G_("incompatible gcc/plugin versions"));
> --
> 2.7.4
>
--
Kees Cook