From 42633ed852deadc14d44660ad71e2f6640239120 Mon Sep 17 00:00:00 2001 From: Sami Tolvanen Date: Thu, 12 Jan 2023 22:49:48 +0000 Subject: [PATCH] kbuild: Fix CFI hash randomization with KASAN Clang emits a asan.module_ctor constructor to each object file when KASAN is enabled, and these functions are indirectly called in do_ctors. With CONFIG_CFI_CLANG, the compiler also emits a CFI type hash before each address-taken global function so they can pass indirect call checks. However, in commit 0c3e806ec0f9 ("x86/cfi: Add boot time hash randomization"), x86 implemented boot time hash randomization, which relies on the .cfi_sites section generated by objtool. As objtool is run against vmlinux.o instead of individual object files with X86_KERNEL_IBT (enabled by default), CFI types in object files that are not part of vmlinux.o end up not being included in .cfi_sites, and thus won't get randomized and trip CFI when called. Only .vmlinux.export.o and init/version-timestamp.o are linked into vmlinux separately from vmlinux.o. As these files don't contain any functions, disable KASAN for both of them to avoid breaking hash randomization. Link: https://github.com/ClangBuiltLinux/linux/issues/1742 Fixes: 0c3e806ec0f9 ("x86/cfi: Add boot time hash randomization") Signed-off-by: Sami Tolvanen Acked-by: Peter Zijlstra (Intel) Signed-off-by: Kees Cook Link: https://lore.kernel.org/r/20230112224948.1479453-2-samitolvanen@google.com --- init/Makefile | 1 + scripts/Makefile.vmlinux | 1 + 2 files changed, 2 insertions(+) diff --git a/init/Makefile b/init/Makefile index 8316c23bead2..26de459006c4 100644 --- a/init/Makefile +++ b/init/Makefile @@ -59,3 +59,4 @@ include/generated/utsversion.h: FORCE $(obj)/version-timestamp.o: include/generated/utsversion.h CFLAGS_version-timestamp.o := -include include/generated/utsversion.h +KASAN_SANITIZE_version-timestamp.o := n diff --git a/scripts/Makefile.vmlinux b/scripts/Makefile.vmlinux index 49946cb96844..10176dec97ea 100644 --- a/scripts/Makefile.vmlinux +++ b/scripts/Makefile.vmlinux @@ -18,6 +18,7 @@ quiet_cmd_cc_o_c = CC $@ $(call if_changed_dep,cc_o_c) ifdef CONFIG_MODULES +KASAN_SANITIZE_.vmlinux.export.o := n targets += .vmlinux.export.o vmlinux: .vmlinux.export.o endif