On Wed, Jan 27, 2021 at 12:15 PM Kees Cook keescook@chromium.org wrote:
On Mon, Jan 25, 2021 at 01:45:25PM +0100, Arnd Bergmann wrote:
From: Arnd Bergmann arnd@arndb.de
I ran into a couple of problems with kunit tests taking too much stack space, sometimes dangerously so. These the the three instances that cause an increase over the warning limit of some architectures:
lib/bitfield_kunit.c:93:1: error: the frame size of 7440 bytes is larger than 2048 bytes [-Werror=frame-larger-than=] drivers/base/test/property-entry-test.c:481:1: error: the frame size of 2640 bytes is larger than 2048 bytes [-Werror=frame-larger-than=] drivers/thunderbolt/test.c:1529:1: error: the frame size of 1176 bytes is larger than 1024 bytes [-Werror=frame-larger-than=]
Ideally there should be a way to rewrite the kunit infrastructure that avoids the explosion of stack data when the structleak plugin is used.
A rather drastic measure would be to use Kconfig logic to make the two options mutually exclusive. This would clearly work, but is probably not needed.
As a simpler workaround, this disables the plugin for the three files in which the excessive stack usage was observed.
ArndArnd Bergmann (3): bitfield: build kunit tests without structleak plugin drivers/base: build kunit tests without structleak plugin thunderbolt: build kunit tests without structleak plugin
drivers/base/test/Makefile | 1 + drivers/thunderbolt/Makefile | 1 + lib/Makefile | 1 + 3 files changed, 3 insertions(+)
I think I'd prefer centralizing the disabling, as done with the other plugins, instead of sprinkling "open coded" command-line options around the kernel's Makefiles. :)
For example:
diff --git a/scripts/Makefile.gcc-plugins b/scripts/Makefile.gcc-plugins index 952e46876329..2d5009e3b593 100644 --- a/scripts/Makefile.gcc-plugins +++ b/scripts/Makefile.gcc-plugins @@ -21,6 +21,10 @@ gcc-plugin-cflags-$(CONFIG_GCC_PLUGIN_STRUCTLEAK_BYREF_ALL) \ += -fplugin-arg-structleak_plugin-byref-all gcc-plugin-cflags-$(CONFIG_GCC_PLUGIN_STRUCTLEAK) \ += -DSTRUCTLEAK_PLUGIN +ifdef CONFIG_GCC_PLUGIN_STRUCTLEAK
- DISABLE_STRUCTLEAK_PLUGIN += -fplugin-arg-structleak_plugin-disable
+endif +export DISABLE_STRUCTLEAK_PLUGIN
gcc-plugin-$(CONFIG_GCC_PLUGIN_RANDSTRUCT) += randomize_layout_plugin.so gcc-plugin-cflags-$(CONFIG_GCC_PLUGIN_RANDSTRUCT) \
And then use DISABLE_STRUCTLEAK_PLUGIN.
This looks fine to me. Does somebody want me to send this out as a patch? Don't want to steal anyone's thunder :-)