From: Sam Ravnborg Date: Wed, 13 Feb 2008 21:43:28 +0000 (+0100) Subject: kbuild: allow -fstack-protector to take effect X-Git-Tag: v2.6.25-rc3~136^2~2 X-Git-Url: https://err.no/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=e06b8b98da071f7dd78fb7822991694288047df0;p=linux-2.6 kbuild: allow -fstack-protector to take effect Arjan van de Ven wrote: === I just read the excellent LWN writeup of the vmsplice security thing, and that got me wondering why this attack wasn't stopped by the CONFIG_CC_STACKPROTECTOR option... because it plain should have been... Some analysis later.. it turns out that the following line in the top level Makefile, added by you in October 2007, entirely disables CONFIG_CC_STACKPROTECTOR ;( With this line removed the exploit will be nicely stopped. CFLAGS += $(call cc-option, -fno-stack-protector) Now I realize that certain distros have patched gcc to compensate for their lack of distro wide CFLAGS, and it's great to work around that... but would there be a way to NOT disable this for CONFIG_CC_STACKPROTECTOR please? It would have made this exploit not possible for those kernels that enable this feature (and that includes distros like Fedora) === Move the assignment to KBUILD_CFLAGS up before including the arch specific Makefile so arch makefiles may override the setting. Signed-off-by: Sam Ravnborg Cc: Arjan van de Ven Cc: stable@kernel.org --- diff --git a/Makefile b/Makefile index c162370c73..d738651883 100644 --- a/Makefile +++ b/Makefile @@ -507,6 +507,10 @@ else KBUILD_CFLAGS += -O2 endif +# Force gcc to behave correct even for buggy distributions +# Arch Makefiles may override this setting +KBUILD_CFLAGS += $(call cc-option, -fno-stack-protector) + include $(srctree)/arch/$(SRCARCH)/Makefile ifdef CONFIG_FRAME_POINTER @@ -525,9 +529,6 @@ ifdef CONFIG_DEBUG_SECTION_MISMATCH KBUILD_CFLAGS += $(call cc-option, -fno-inline-functions-called-once) endif -# Force gcc to behave correct even for buggy distributions -KBUILD_CFLAGS += $(call cc-option, -fno-stack-protector) - # arch Makefile may override CC so keep this after arch Makefile is included NOSTDINC_FLAGS += -nostdinc -isystem $(shell $(CC) -print-file-name=include) CHECKFLAGS += $(NOSTDINC_FLAGS)