* [PATCH v2 1/1] stackleak: Register the 'stackleak_cleanup' pass before the '*free_cfg' pass
@ 2018-12-06 15:13 Alexander Popov
2018-12-06 18:25 ` Kees Cook
0 siblings, 1 reply; 2+ messages in thread
From: Alexander Popov @ 2018-12-06 15:13 UTC (permalink / raw)
To: kernel-hardening, Kees Cook, Jann Horn, Andy Lutomirski,
Borislav Petkov, Thomas Gleixner, Dave Hansen, Steven Rostedt,
Peter Zijlstra, Masami Hiramatsu, Florian Weimer,
Richard Sandiford, Segher Boessenkool, Alexander Monakov,
Tycho Andersen, Laura Abbott, Mark Rutland, Emese Revfy,
Thomas Garnier, Ingo Molnar, Will Deacon, Alexei Starovoitov,
Ard Biesheuvel, H Peter Anvin, David S Miller, linux-arm-kernel,
gcc, alex.popov, linux-kernel
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 '*free_cfg' pass. It's the moment when the stack frame size is
already final, function prologues and epilogues are generated, and the
machine-dependent code transformations are not done.
[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>
---
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..dbd3746 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 "*free_cfg"
+ * pass. It's the moment when the stack frame size is already final,
+ * function prologues and epilogues are generated, and the
+ * machine-dependent code transformations are not done.
*/
- PASS_INFO(stackleak_cleanup, "reload", 1, PASS_POS_INSERT_AFTER);
+ PASS_INFO(stackleak_cleanup, "*free_cfg", 1, PASS_POS_INSERT_BEFORE);
if (!plugin_default_version_check(version, &gcc_version)) {
error(G_("incompatible gcc/plugin versions"));
--
2.7.4
^ permalink raw reply [flat|nested] 2+ messages in thread* Re: [PATCH v2 1/1] stackleak: Register the 'stackleak_cleanup' pass before the '*free_cfg' pass
2018-12-06 15:13 [PATCH v2 1/1] stackleak: Register the 'stackleak_cleanup' pass before the '*free_cfg' pass Alexander Popov
@ 2018-12-06 18:25 ` Kees Cook
0 siblings, 0 replies; 2+ messages in thread
From: Kees Cook @ 2018-12-06 18:25 UTC (permalink / raw)
To: Alexander Popov
Cc: Kernel Hardening, Jann Horn, Andy Lutomirski, Borislav Petkov,
Thomas Gleixner, Dave Hansen, Steven Rostedt, Peter Zijlstra,
Masami Hiramatsu, Florian Weimer, Richard Sandiford,
Segher Boessenkool, amonakov, Tycho Andersen, Laura Abbott,
Mark Rutland, Emese Revfy, Thomas Garnier, Ingo Molnar,
Will Deacon, Alexei Starovoitov, Ard Biesheuvel, H. Peter Anvin,
David S. Miller, linux-arm-kernel, gcc, LKML
On Thu, Dec 6, 2018 at 7:13 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 '*free_cfg' pass. It's the moment when the stack frame size is
> already final, function prologues and epilogues are generated, and the
> machine-dependent code transformations are not done.
>
> [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! I've applied this to me tree and I'll send a pull request soon.
-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..dbd3746 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 "*free_cfg"
> + * pass. It's the moment when the stack frame size is already final,
> + * function prologues and epilogues are generated, and the
> + * machine-dependent code transformations are not done.
> */
> - PASS_INFO(stackleak_cleanup, "reload", 1, PASS_POS_INSERT_AFTER);
> + PASS_INFO(stackleak_cleanup, "*free_cfg", 1, PASS_POS_INSERT_BEFORE);
>
> if (!plugin_default_version_check(version, &gcc_version)) {
> error(G_("incompatible gcc/plugin versions"));
> --
> 2.7.4
>
--
Kees Cook
^ permalink raw reply [flat|nested] 2+ messages in thread
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2018-12-06 15:13 [PATCH v2 1/1] stackleak: Register the 'stackleak_cleanup' pass before the '*free_cfg' pass Alexander Popov
2018-12-06 18:25 ` Kees Cook
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