Patch "ACPI: APEI: GHES: Disable KASAN instrumentation when compile testing with clang < 18" has been added to the 6.12-stable tree

DISCUSSION Nathan Chancellor 2 participants 2 messages Mar 9 1 message not in the archive

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Stable branch ACPI ACPI APEI

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Nathan Chancellor

author

2026-03-09 21:28 UTC #1 lore raw

Quoted 55 lines · Sasha Levin

This is a note to let you know that I've just added the patch titled
ACPI: APEI: GHES: Disable KASAN instrumentation when compile testing with clang < 18
to the 6.12-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
acpi-apei-ghes-disable-kasan-instrumentation-when-co.patch
and it can be found in the queue-6.12 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.
commit ccd3cab8095d5c53eaf8a6598ff339ffaad6a696
Author: Nathan Chancellor <[email protected]>
Date:   Wed Jan 14 16:27:11 2026 -0700
ACPI: APEI: GHES: Disable KASAN instrumentation when compile testing with clang < 18
[ Upstream commit b584bfbd7ec417f257f651cc00a90c66e31dfbf1 ]
After a recent innocuous change to drivers/acpi/apei/ghes.c, building ARCH=arm64 allmodconfig with clang-17 or older (which has both CONFIG_KASAN=y and CONFIG_WERROR=y) fails with:
drivers/acpi/apei/ghes.c:902:13: error: stack frame size (2768) exceeds limit (2048) in 'ghes_do_proc' [-Werror,-Wframe-larger-than]
902 | static void ghes_do_proc(struct ghes *ghes,
| ^
A KASAN pass that removes unneeded stack instrumentation, enabled by default in clang-18 [1], drastically improves stack usage in this case.
To avoid the warning in the common allmodconfig case when it can break the build, disable KASAN for ghes.o when compile testing with clang-17 and older. Disabling KASAN outright may hide legitimate runtime issues, so live with the warning in that case; the user can either increase the frame warning limit or disable -Werror, which they should probably do when debugging with KASAN anyways.
Closes https://github.com/ClangBuiltLinux/linux/issues/2148
Link https://github.com/llvm/llvm-project/commit/51fbab134560ece663517bf1e8c2a30300d08f1a [1]
Signed-off-by Nathan Chancellor <[email protected]>
Cc All applicable <[email protected]>
Link https://patch.msgid.link/20260114-ghes-avoid-wflt-clang-older-than-18-v1-1-9c8248bfe4f4@kernel.org open here
Signed-off-by Rafael J. Wysocki <[email protected]>
Signed-off-by Sasha Levin <[email protected]>
drivers/acpi/apei/Makefile +0 -0
index 5db61dfb46915..1a0b85923cd42 100644

drivers/acpi/apei/Makefile line 10

Quoted 10 lines

drivers/acpi/apei/Makefile +4 -0

@@ -1,6 +1,10 @@
 # SPDX-License-Identifier: GPL-2.0
 obj-$(CONFIG_ACPI_APEI)		+= apei.o
 obj-$(CONFIG_ACPI_APEI_GHES)	+= ghes.o
+# clang versions prior to 18 may blow out the stack with KASAN
+ifeq ($(CONFIG_COMPILE_TEST)_$(CONFIG_CC_IS_CLANG)_$(call clang-min-version, 180000),y_y_)
+KASAN_SANITIZE_ghes.o := n
+endif
 obj-$(CONFIG_ACPI_APEI_PCIEAER)	+= ghes_helpers.o
 obj-$(CONFIG_ACPI_APEI_EINJ)	+= einj.o
 einj-y				:= einj-core.o

The backports you have taken to make this apply cleanly to 6.12

[email protected]
[email protected]
[email protected]
[email protected]

are excessive in my opinion. I think you should just address the conflict... There is absolutely no dependency on those changes so "Stable-dep-of" is a bit misleading.

drivers/acpi/apei/Makefile +4 -0

index 2c474e6477e1..346cdf0a0ef9 100644
@@ -1,6 +1,10 @@
 # SPDX-License-Identifier: GPL-2.0
 obj-$(CONFIG_ACPI_APEI)		+= apei.o
 obj-$(CONFIG_ACPI_APEI_GHES)	+= ghes.o
+# clang versions prior to 18 may blow out the stack with KASAN
+ifeq ($(CONFIG_COMPILE_TEST)_$(CONFIG_CC_IS_CLANG)_$(call clang-min-version, 180000),y_y_)
+KASAN_SANITIZE_ghes.o := n
+endif
 obj-$(CONFIG_ACPI_APEI_EINJ)	+= einj.o
 einj-y				:= einj-core.o
 einj-$(CONFIG_ACPI_APEI_EINJ_CXL) += einj-cxl.o

Sasha Levin

maintainer

2026-03-09 22:25 UTC #2 lore raw

Quoted 69 lines · Nathan Chancellor

Quoted 55 lines · Sasha Levin
This is a note to let you know that I've just added the patch titled
ACPI: APEI: GHES: Disable KASAN instrumentation when compile testing with clang < 18
to the 6.12-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
acpi-apei-ghes-disable-kasan-instrumentation-when-co.patch
and it can be found in the queue-6.12 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.
commit ccd3cab8095d5c53eaf8a6598ff339ffaad6a696
Author: Nathan Chancellor <[email protected]>
Date:   Wed Jan 14 16:27:11 2026 -0700
ACPI: APEI: GHES: Disable KASAN instrumentation when compile testing with clang < 18
[ Upstream commit b584bfbd7ec417f257f651cc00a90c66e31dfbf1 ]
After a recent innocuous change to drivers/acpi/apei/ghes.c, building ARCH=arm64 allmodconfig with clang-17 or older (which has both CONFIG_KASAN=y and CONFIG_WERROR=y) fails with:
drivers/acpi/apei/ghes.c:902:13: error: stack frame size (2768) exceeds limit (2048) in 'ghes_do_proc' [-Werror,-Wframe-larger-than]
902 | static void ghes_do_proc(struct ghes *ghes,
| ^
A KASAN pass that removes unneeded stack instrumentation, enabled by default in clang-18 [1], drastically improves stack usage in this case.
To avoid the warning in the common allmodconfig case when it can break the build, disable KASAN for ghes.o when compile testing with clang-17 and older. Disabling KASAN outright may hide legitimate runtime issues, so live with the warning in that case; the user can either increase the frame warning limit or disable -Werror, which they should probably do when debugging with KASAN anyways.
Closes https://github.com/ClangBuiltLinux/linux/issues/2148
Link https://github.com/llvm/llvm-project/commit/51fbab134560ece663517bf1e8c2a30300d08f1a [1]
Signed-off-by Nathan Chancellor <[email protected]>
Cc All applicable <[email protected]>
Link https://patch.msgid.link/20260114-ghes-avoid-wflt-clang-older-than-18-v1-1-9c8248bfe4f4@kernel.org open here
Signed-off-by Rafael J. Wysocki <[email protected]>
Signed-off-by Sasha Levin <[email protected]>
drivers/acpi/apei/Makefile +0 -0
index 5db61dfb46915..1a0b85923cd42 100644
drivers/acpi/apei/Makefile line 10
Quoted 10 lines
drivers/acpi/apei/Makefile +4 -0
@@ -1,6 +1,10 @@
 # SPDX-License-Identifier: GPL-2.0
 obj-$(CONFIG_ACPI_APEI)		+= apei.o
 obj-$(CONFIG_ACPI_APEI_GHES)	+= ghes.o
+# clang versions prior to 18 may blow out the stack with KASAN
+ifeq ($(CONFIG_COMPILE_TEST)_$(CONFIG_CC_IS_CLANG)_$(call clang-min-version, 180000),y_y_)
+KASAN_SANITIZE_ghes.o := n
+endif
 obj-$(CONFIG_ACPI_APEI_PCIEAER)	+= ghes_helpers.o
 obj-$(CONFIG_ACPI_APEI_EINJ)	+= einj.o
 einj-y				:= einj-core.o
The backports you have taken to make this apply cleanly to 6.12

Quoted 8 lines

[email protected]
[email protected]
[email protected]
[email protected]
are excessive in my opinion. I think you should just address the conflict... There is absolutely no dependency on those changes so "Stable-dep-of" is a bit misleading.

ack

Signature · 2 lines

Thanks,
Sasha