[PATCH 5.15 219/279] s390/vdso: filter out -mstack-guard and -mstack-size

Greg Kroah-Hartman
2021-11-24T14:02:54Z

From: Sven Schnelle <svens@linux.ibm.com>

commit 00b55eaf45549ce26424224d069a091c7e5d8bac upstream.

When CONFIG_VMAP_STACK is disabled, the user can enable CONFIG_STACK_CHECK,
which adds a stack overflow check to each C function in the kernel. This is
also done for functions in the vdso page. These functions are run in user
context and user stack sizes are usually different to what the kernel uses.
This might trigger the stack check although the stack size is valid.
Therefore filter the -mstack-guard and -mstack-size flags when compiling
vdso C files.

Cc: stable@kernel.org # 5.10+
Fixes: 4bff8cb54502 ("s390: convert to GENERIC_VDSO")
Reported-by: Janosch Frank <frankja@linux.ibm.com>
Signed-off-by: Sven Schnelle <svens@linux.ibm.com>
Reviewed-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
arch/s390/Makefile | 10 ++++++----
arch/s390/kernel/vdso64/Makefile | 5 +++--
2 files changed, 9 insertions(+), 6 deletions(-)

--- a/arch/s390/Makefile
+++ b/arch/s390/Makefile
@@ -79,10 +79,12 @@ KBUILD_AFLAGS_DECOMPRESSOR += $(aflags-y
KBUILD_CFLAGS_DECOMPRESSOR += $(cflags-y)

ifneq ($(call cc-option,-mstack-size=8192 -mstack-guard=128),)
-cflags-$(CONFIG_CHECK_STACK) += -mstack-size=$(STACK_SIZE)
-ifeq ($(call cc-option,-mstack-size=8192),)
-cflags-$(CONFIG_CHECK_STACK) += -mstack-guard=$(CONFIG_STACK_GUARD)
-endif
+ CC_FLAGS_CHECK_STACK := -mstack-size=$(STACK_SIZE)
+ ifeq ($(call cc-option,-mstack-size=8192),)
+ CC_FLAGS_CHECK_STACK += -mstack-guard=$(CONFIG_STACK_GUARD)
+ endif
+ export CC_FLAGS_CHECK_STACK
+ cflags-$(CONFIG_CHECK_STACK) += $(CC_FLAGS_CHECK_STACK)
endif

ifdef CONFIG_EXPOLINE
--- a/arch/s390/kernel/vdso64/Makefile
+++ b/arch/s390/kernel/vdso64/Makefile
@@ -8,8 +8,9 @@ ARCH_REL_TYPE_ABS += R_390_GOT|R_390_PLT
include $(srctree)/lib/vdso/Makefile
obj-vdso64 = vdso_user_wrapper.o note.o
obj-cvdso64 = vdso64_generic.o getcpu.o
-CFLAGS_REMOVE_getcpu.o = -pg $(CC_FLAGS_FTRACE) $(CC_FLAGS_EXPOLINE)
-CFLAGS_REMOVE_vdso64_generic.o = -pg $(CC_FLAGS_FTRACE) $(CC_FLAGS_EXPOLINE)
+VDSO_CFLAGS_REMOVE := -pg $(CC_FLAGS_FTRACE) $(CC_FLAGS_EXPOLINE) $(CC_FLAGS_CHECK_STACK)
+CFLAGS_REMOVE_getcpu.o = $(VDSO_CFLAGS_REMOVE)
+CFLAGS_REMOVE_vdso64_generic.o = $(VDSO_CFLAGS_REMOVE)

# Build rules