From: Arnd Bergmann Date: Fri, 6 Mar 2026 15:05:49 +0000 (+0100) Subject: ubsan: turn off kmsan inside of ubsan instrumentation X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=d7651089939bf00fe033845e662905ce750b1f18;p=thirdparty%2Flinux.git ubsan: turn off kmsan inside of ubsan instrumentation The structure initialization in the two type mismatch handling functions causes a call to __msan_memset() to be generated inside of a UACCESS block, which in turn leads to an objtool warning about possibly leaking uaccess-enabled state: lib/ubsan.o: warning: objtool: __ubsan_handle_type_mismatch+0xda: call to __msan_memset() with UACCESS enabled lib/ubsan.o: warning: objtool: __ubsan_handle_type_mismatch_v1+0xf4: call to __msan_memset() with UACCESS enabled Most likely __msan_memset() is safe to be called here and could be added to the uaccess_safe_builtin[] list of safe functions, but seeing that the ubsan file itself already has kasan, ubsan and kcsan disabled itself, it is probably a good idea to also turn off kmsan here, in particular this also avoids the risk of recursing between ubsan and kcsan checks in other functions of this file. I saw this happen while testing randconfig builds with clang-22, but did not try older versions, or attempt to see which kernel change introduced the warning. Link: https://lkml.kernel.org/r/20260306150613.350029-1-arnd@kernel.org Signed-off-by: Arnd Bergmann Acked-by: Andrey Ryabinin Cc: Kees Cook Cc: Marco Elver Cc: Andrey Konovalov Cc: Bill Wendling Cc: Justin Stitt Cc: Nathan Chancellor Cc: Peter Zijlstra Signed-off-by: Andrew Morton --- diff --git a/lib/Makefile b/lib/Makefile index 1b9ee167517f3..ce3ae929ae8c3 100644 --- a/lib/Makefile +++ b/lib/Makefile @@ -307,6 +307,7 @@ obj-$(CONFIG_UBSAN) += ubsan.o UBSAN_SANITIZE_ubsan.o := n KASAN_SANITIZE_ubsan.o := n KCSAN_SANITIZE_ubsan.o := n +KMSAN_SANITIZE_ubsan.o := n CFLAGS_ubsan.o := -fno-stack-protector $(DISABLE_KSTACK_ERASE) obj-$(CONFIG_SBITMAP) += sbitmap.o