[PATCH 6.12 021/567] kbuild: Use objtree for module signing key path

Greg Kroah-Hartman
2026-01-06T17:15:27Z

From: Mikhail Malyshev <mike.malyshev@gmail.com>

[ Upstream commit af61da281f52aba0c5b090bafb3a31c5739850ff ]

When building out-of-tree modules with CONFIG_MODULE_SIG_FORCE=y,
module signing fails because the private key path uses $(srctree)
while the public key path uses $(objtree). Since signing keys are
generated in the build directory during kernel compilation, both
paths should use $(objtree) for consistency.

This causes SSL errors like:
SSL error:02001002:system library:fopen:No such file or directory
sign-file: /kernel-src/certs/signing_key.pem

The issue occurs because:
- sig-key uses: $(srctree)/certs/signing_key.pem (source tree)
- cmd_sign uses: $(objtree)/certs/signing_key.x509 (build tree)

But both keys are generated in $(objtree) during the build.

This complements commit 25ff08aa43e37 ("kbuild: Fix signing issue for
external modules") which fixed the scripts path and public key path,
but missed the private key path inconsistency.

Fixes out-of-tree module signing for configurations with separate
source and build directories (e.g., O=/kernel-out).

Signed-off-by: Mikhail Malyshev <mike.malyshev@gmail.com>
Reviewed-by: Nathan Chancellor <nathan@kernel.org>
Tested-by: Nicolas Schier <nsc@kernel.org>
Link: https://patch.msgid.link/20251015163452.3754286-1-mike.malyshev@gmail.com
Signed-off-by: Nicolas Schier <nsc@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
scripts/Makefile.modinst | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/scripts/Makefile.modinst b/scripts/Makefile.modinst
index d977209431898..5dd52788a042a 100644
--- a/scripts/Makefile.modinst
+++ b/scripts/Makefile.modinst
@@ -100,7 +100,7 @@ endif
# Don't stop modules_install even if we can't sign external modules.
#
ifeq ($(filter pkcs11:%, $(CONFIG_MODULE_SIG_KEY)),)
-sig-key := $(if $(wildcard $(CONFIG_MODULE_SIG_KEY)),,$(srctree)/)$(CONFIG_MODULE_SIG_KEY)
+sig-key := $(if $(wildcard $(CONFIG_MODULE_SIG_KEY)),,$(objtree)/)$(CONFIG_MODULE_SIG_KEY)
else
sig-key := $(CONFIG_MODULE_SIG_KEY)
endif
--
2.51.0