FAILED: patch "[PATCH] KVM: selftests: Add -U_FORTIFY_SOURCE to avoid some" failed to apply to 6.12-stable tree

The patch below does not apply to the 6.12-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.12.y
git checkout FETCH_HEAD
git cherry-pick -x e396a74222654486d6ab45dca5d0c54c408b8b91
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2026020754-payback-platonic-6ee5@gregkh' --subject-prefix 'PATCH 6.12.y' HEAD^..

Possible dependencies:

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From e396a74222654486d6ab45dca5d0c54c408b8b91 Mon Sep 17 00:00:00 2001
From: Zhiquan Li <[email protected]>
Date: Thu, 22 Jan 2026 13:35:50 +0800
Subject: [PATCH] KVM: selftests: Add -U_FORTIFY_SOURCE to avoid some
unpredictable test failures

Some distributions (such as Ubuntu) configure GCC so that _FORTIFY_SOURCE is automatically enabled at -O1 or above. This results in some fortified version of definitions of standard library functions are included. While linker resolves the symbols, the fortified versions might override the definitions in lib/string_override.c and reference to those PLT entries in GLIBC. This is not a problem for the code in host, but it is a disaster for the guest code. E.g., if build and run x86/nested_emulation_test on Ubuntu 24.04 will encounter a L1 #PF due to memset() reference to __memset_chk@plt.

The option -fno-builtin-memset is not helpful here, because those fortified versions are not built-in but some definitions which are included by header, they are for different intentions.

In order to eliminate the unpredictable behaviors may vary depending on the linker and platform, add the "-U_FORTIFY_SOURCE" into CFLAGS to prevent from introducing the fortified definitions.

index ba5c2b643efa..d45bf4ccb3bf 100644
@@ -251,6 +251,7 @@ LINUX_TOOL_INCLUDE = $(top_srcdir)/tools/include
 LINUX_TOOL_ARCH_INCLUDE = $(top_srcdir)/tools/arch/$(ARCH)/include
 CFLAGS += -Wall -Wstrict-prototypes -Wuninitialized -O2 -g -std=gnu99 \
 	-Wno-gnu-variable-sized-type-not-at-end -MD -MP -DCONFIG_64BIT \
+	-U_FORTIFY_SOURCE \
 	-fno-builtin-memcmp -fno-builtin-memcpy \
 	-fno-builtin-memset -fno-builtin-strnlen \
 	-fno-stack-protector -fno-PIE -fno-strict-aliasing \

From: Zhiquan Li <[email protected]>

[ Upstream commit e396a74222654486d6ab45dca5d0c54c408b8b91 ]

Some distributions (such as Ubuntu) configure GCC so that _FORTIFY_SOURCE is automatically enabled at -O1 or above. This results in some fortified version of definitions of standard library functions are included. While linker resolves the symbols, the fortified versions might override the definitions in lib/string_override.c and reference to those PLT entries in GLIBC. This is not a problem for the code in host, but it is a disaster for the guest code. E.g., if build and run x86/nested_emulation_test on Ubuntu 24.04 will encounter a L1 #PF due to memset() reference to __memset_chk@plt.

The option -fno-builtin-memset is not helpful here, because those fortified versions are not built-in but some definitions which are included by header, they are for different intentions.

In order to eliminate the unpredictable behaviors may vary depending on the linker and platform, add the "-U_FORTIFY_SOURCE" into CFLAGS to prevent from introducing the fortified definitions.

---
 tools/testing/selftests/kvm/Makefile | 1 +
 1 file changed, 1 insertion(+)

index 48645a2e29da9..9d6fab359ae3c 100644
@@ -239,6 +239,7 @@ LINUX_TOOL_ARCH_INCLUDE = $(top_srcdir)/tools/arch/$(ARCH)/include
 endif
 CFLAGS += -Wall -Wstrict-prototypes -Wuninitialized -O2 -g -std=gnu99 \
 	-Wno-gnu-variable-sized-type-not-at-end -MD -MP -DCONFIG_64BIT \
+	-U_FORTIFY_SOURCE \
 	-fno-builtin-memcmp -fno-builtin-memcpy \
 	-fno-builtin-memset -fno-builtin-strnlen \
 	-fno-stack-protector -fno-PIE -fno-strict-aliasing \

2.51.0