diff options
| author | Kees Cook <keescook@chromium.org> | 2024-05-01 02:02:22 +0200 |
|---|---|---|
| committer | Kees Cook <kees@kernel.org> | 2024-06-19 21:41:08 +0200 |
| commit | d6f635bcaca8d38dfa47ee20658705f9eff156b5 (patch) | |
| tree | 22797324cba2df59d8c04d42d95e71884bc39e85 | |
| parent | lkdtm/bugs: add test for hung smp_call_function_single() (diff) | |
| download | linux-d6f635bcaca8d38dfa47ee20658705f9eff156b5.tar.xz linux-d6f635bcaca8d38dfa47ee20658705f9eff156b5.zip | |
x86/alternatives: Make FineIBT mode Kconfig selectable
Since FineIBT performs checking at the destination, it is weaker against
attacks that can construct arbitrary executable memory contents. As such,
some system builders want to run with FineIBT disabled by default. Allow
the "cfi=kcfi" boot param mode to be selectable through Kconfig via the
newly introduced CONFIG_CFI_AUTO_DEFAULT.
Reviewed-by: Sami Tolvanen <samitolvanen@google.com>
Reviewed-by: Nathan Chancellor <nathan@kernel.org>
Tested-by: Nathan Chancellor <nathan@kernel.org>
Link: https://lore.kernel.org/r/20240501000218.work.998-kees@kernel.org
Signed-off-by: Kees Cook <kees@kernel.org>
| -rw-r--r-- | arch/x86/Kconfig | 9 | ||||
| -rw-r--r-- | arch/x86/include/asm/cfi.h | 2 | ||||
| -rw-r--r-- | arch/x86/kernel/alternative.c | 8 |
3 files changed, 14 insertions, 5 deletions
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig index 1d7122a1883e..56e301921d2a 100644 --- a/arch/x86/Kconfig +++ b/arch/x86/Kconfig @@ -2427,6 +2427,15 @@ config STRICT_SIGALTSTACK_SIZE Say 'N' unless you want to really enforce this check. +config CFI_AUTO_DEFAULT + bool "Attempt to use FineIBT by default at boot time" + depends on FINEIBT + default y + help + Attempt to use FineIBT by default at boot time. If enabled, + this is the same as booting with "cfi=auto". If disabled, + this is the same as booting with "cfi=kcfi". + source "kernel/livepatch/Kconfig" endmenu diff --git a/arch/x86/include/asm/cfi.h b/arch/x86/include/asm/cfi.h index 7cd752557905..31d19c815f99 100644 --- a/arch/x86/include/asm/cfi.h +++ b/arch/x86/include/asm/cfi.h @@ -93,7 +93,7 @@ * */ enum cfi_mode { - CFI_DEFAULT, /* FineIBT if hardware has IBT, otherwise kCFI */ + CFI_AUTO, /* FineIBT if hardware has IBT, otherwise kCFI */ CFI_OFF, /* Taditional / IBT depending on .config */ CFI_KCFI, /* Optionally CALL_PADDING, IBT, RETPOLINE */ CFI_FINEIBT, /* see arch/x86/kernel/alternative.c */ diff --git a/arch/x86/kernel/alternative.c b/arch/x86/kernel/alternative.c index 89de61243272..7fcba437abae 100644 --- a/arch/x86/kernel/alternative.c +++ b/arch/x86/kernel/alternative.c @@ -885,8 +885,8 @@ void __init_or_module apply_seal_endbr(s32 *start, s32 *end) { } #endif /* CONFIG_X86_KERNEL_IBT */ -#ifdef CONFIG_FINEIBT -#define __CFI_DEFAULT CFI_DEFAULT +#ifdef CONFIG_CFI_AUTO_DEFAULT +#define __CFI_DEFAULT CFI_AUTO #elif defined(CONFIG_CFI_CLANG) #define __CFI_DEFAULT CFI_KCFI #else @@ -994,7 +994,7 @@ static __init int cfi_parse_cmdline(char *str) } if (!strcmp(str, "auto")) { - cfi_mode = CFI_DEFAULT; + cfi_mode = CFI_AUTO; } else if (!strcmp(str, "off")) { cfi_mode = CFI_OFF; cfi_rand = false; @@ -1254,7 +1254,7 @@ static void __apply_fineibt(s32 *start_retpoline, s32 *end_retpoline, "FineIBT preamble wrong size: %ld", fineibt_preamble_size)) return; - if (cfi_mode == CFI_DEFAULT) { + if (cfi_mode == CFI_AUTO) { cfi_mode = CFI_KCFI; if (HAS_KERNEL_IBT && cpu_feature_enabled(X86_FEATURE_IBT)) cfi_mode = CFI_FINEIBT; |