linux-kernel - [PATCH] Makefile: Fix empty flag results for stackprotector

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Message-ID: <20171016040333.GA82643@beast>
Date:   Sun, 15 Oct 2017 21:03:33 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     linux-kernel@...r.kernel.org,
        Robert Jarzmik <robert.jarzmik@...e.fr>
Subject: [PATCH] Makefile: Fix empty flag results for stackprotector _AUTO
 mode

If the compiler didn't support any stackprotector mode, the second
empty test would still trip. This moves it to an "else" test for the
non-AUTO modes.

Reported-and-tested-by: Robert Jarzmik <robert.jarzmik@...e.fr>
Signed-off-by: Kees Cook <keescook@...omium.org>
---
This is a separate fix from the issue with gcc 4.4.4. Yay compilers.
(Also, this is technically a v2 with just the commit message changed.)
---
 Makefile | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/Makefile b/Makefile
index 20fafb48fdf9..74d5f037df69 100644
--- a/Makefile
+++ b/Makefile
@@ -1093,16 +1093,17 @@ PHONY += prepare-compiler-check
 prepare-compiler-check: FORCE
 # Make sure compiler supports requested stack protector flag.
 ifdef stackp-name
-  # Warn about CONFIG_CC_STACKPROTECTOR_AUTO having found no option.
   ifeq ($(stackp-flag),)
+	# Warn about CONFIG_CC_STACKPROTECTOR_AUTO having found no option.
 	@echo CONFIG_CC_STACKPROTECTOR_$(stackp-name): \
 		  Compiler does not support any known stack-protector >&2
-  endif
-  # Fail if specifically requested stack protector is missing.
+  else
   ifeq ($(call cc-option, $(stackp-flag)),)
+	# Fail if specifically requested stack protector is missing.
 	@echo Cannot use CONFIG_CC_STACKPROTECTOR_$(stackp-name): \
 		  $(stackp-flag) not supported by compiler >&2 && exit 1
   endif
+  endif
 endif
 # Make sure compiler does not have buggy stack-protector support.
 ifdef stackp-check
-- 
2.7.4


-- 
Kees Cook
Pixel Security