On Tue, Feb 12, 2008 at 09:00:01AM -0800, Arjan van de Ven wrote: > > Hi, > > 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. > > # Force gcc to behave correct even for buggy distributions > 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)
I guess the problem is that we in arch/x86/Makefile enable the stackprotector but then later in the main Makefile disables it. So the right way to approach this should be to always disable it and the reenable it in the arch Makefile. So something like this? Sam diff --git a/Makefile b/Makefile index c162370..7ccf6f5 100644 --- a/Makefile +++ b/Makefile @@ -507,6 +507,9 @@ else KBUILD_CFLAGS += -O2 endif +# Force gcc to behave correct even for buggy distributions +KBUILD_CFLAGS += $(call cc-option, -fno-stack-protector) + include $(srctree)/arch/$(SRCARCH)/Makefile ifdef CONFIG_FRAME_POINTER @@ -525,9 +528,6 @@ 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) -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/