The initially proposed KASAN command line parameters are redundant. This change drops the complex "kasan.mode=off/prod/full" parameter and adds a simpler kill switch "kasan=off/on" instead. The new parameter together with the already existing ones provides a cleaner way to express the same set of features. The full set of parameters with this change: kasan=off/on - whether KASAN is enabled kasan.fault=report/panic - whether to only print a report or also panic kasan.stacktrace=off/on - whether to collect alloc/free stack traces Default values: kasan=on kasan.fault=report kasan.stacktrace=on (if CONFIG_DEBUG_KERNEL=y) kasan.stacktrace=off (otherwise) Link: https://linux-review.googlesource.com/id/Ib3694ed90b1e8ccac6cf77dfd301847af4aba7b8 Signed-off-by: Andrey Konovalov <andreyknvl@xxxxxxxxxx> --- Documentation/dev-tools/kasan.rst | 27 +++-------- mm/kasan/hw_tags.c | 77 +++++++++++++------------------ 2 files changed, 38 insertions(+), 66 deletions(-) diff --git a/Documentation/dev-tools/kasan.rst b/Documentation/dev-tools/kasan.rst index 0fc3fb1860c4..1651d961f06a 100644 --- a/Documentation/dev-tools/kasan.rst +++ b/Documentation/dev-tools/kasan.rst @@ -160,29 +160,14 @@ intended for use in production as a security mitigation. Therefore it supports boot parameters that allow to disable KASAN competely or otherwise control particular KASAN features. -The things that can be controlled are: +- ``kasan=off`` or ``=on`` controls whether KASAN is enabled (default: ``on``). -1. Whether KASAN is enabled at all. -2. Whether KASAN collects and saves alloc/free stacks. -3. Whether KASAN panics on a detected bug or not. +- ``kasan.stacktrace=off`` or ``=on`` disables or enables alloc and free stack + traces collection (default: ``on`` for ``CONFIG_DEBUG_KERNEL=y``, otherwise + ``off``). -The ``kasan.mode`` boot parameter allows to choose one of three main modes: - -- ``kasan.mode=off`` - KASAN is disabled, no tag checks are performed -- ``kasan.mode=prod`` - only essential production features are enabled -- ``kasan.mode=full`` - all KASAN features are enabled - -The chosen mode provides default control values for the features mentioned -above. However it's also possible to override the default values by providing: - -- ``kasan.stacktrace=off`` or ``=on`` - enable alloc/free stack collection - (default: ``on`` for ``mode=full``, - otherwise ``off``) -- ``kasan.fault=report`` or ``=panic`` - only print KASAN report or also panic - (default: ``report``) - -If ``kasan.mode`` parameter is not provided, it defaults to ``full`` when -``CONFIG_DEBUG_KERNEL`` is enabled, and to ``prod`` otherwise. +- ``kasan.fault=report`` or ``=panic`` controls whether to only print a KASAN + report or also panic the kernel (default: ``report``). For developers ~~~~~~~~~~~~~~ diff --git a/mm/kasan/hw_tags.c b/mm/kasan/hw_tags.c index 55bd6f09c70f..e529428e7a11 100644 --- a/mm/kasan/hw_tags.c +++ b/mm/kasan/hw_tags.c @@ -19,11 +19,10 @@ #include "kasan.h" -enum kasan_arg_mode { - KASAN_ARG_MODE_DEFAULT, - KASAN_ARG_MODE_OFF, - KASAN_ARG_MODE_PROD, - KASAN_ARG_MODE_FULL, +enum kasan_arg { + KASAN_ARG_DEFAULT, + KASAN_ARG_OFF, + KASAN_ARG_ON, }; enum kasan_arg_stacktrace { @@ -38,7 +37,7 @@ enum kasan_arg_fault { KASAN_ARG_FAULT_PANIC, }; -static enum kasan_arg_mode kasan_arg_mode __ro_after_init; +static enum kasan_arg kasan_arg __ro_after_init; static enum kasan_arg_stacktrace kasan_arg_stacktrace __ro_after_init; static enum kasan_arg_fault kasan_arg_fault __ro_after_init; @@ -52,26 +51,24 @@ DEFINE_STATIC_KEY_FALSE(kasan_flag_stacktrace); /* Whether panic or disable tag checking on fault. */ bool kasan_flag_panic __ro_after_init; -/* kasan.mode=off/prod/full */ -static int __init early_kasan_mode(char *arg) +/* kasan=off/on */ +static int __init early_kasan_flag(char *arg) { if (!arg) return -EINVAL; if (!strcmp(arg, "off")) - kasan_arg_mode = KASAN_ARG_MODE_OFF; - else if (!strcmp(arg, "prod")) - kasan_arg_mode = KASAN_ARG_MODE_PROD; - else if (!strcmp(arg, "full")) - kasan_arg_mode = KASAN_ARG_MODE_FULL; + kasan_arg = KASAN_ARG_OFF; + else if (!strcmp(arg, "on")) + kasan_arg = KASAN_ARG_ON; else return -EINVAL; return 0; } -early_param("kasan.mode", early_kasan_mode); +early_param("kasan", early_kasan_flag); -/* kasan.stack=off/on */ +/* kasan.stacktrace=off/on */ static int __init early_kasan_flag_stacktrace(char *arg) { if (!arg) @@ -113,8 +110,8 @@ void kasan_init_hw_tags_cpu(void) * as this function is only called for MTE-capable hardware. */ - /* If KASAN is disabled, do nothing. */ - if (kasan_arg_mode == KASAN_ARG_MODE_OFF) + /* If KASAN is disabled via command line, don't initialize it. */ + if (kasan_arg == KASAN_ARG_OFF) return; hw_init_tags(KASAN_TAG_MAX); @@ -124,43 +121,28 @@ void kasan_init_hw_tags_cpu(void) /* kasan_init_hw_tags() is called once on boot CPU. */ void __init kasan_init_hw_tags(void) { - /* If hardware doesn't support MTE, do nothing. */ + /* If hardware doesn't support MTE, don't initialize KASAN. */ if (!system_supports_mte()) return; - /* Choose KASAN mode if kasan boot parameter is not provided. */ - if (kasan_arg_mode == KASAN_ARG_MODE_DEFAULT) { - if (IS_ENABLED(CONFIG_DEBUG_KERNEL)) - kasan_arg_mode = KASAN_ARG_MODE_FULL; - else - kasan_arg_mode = KASAN_ARG_MODE_PROD; - } - - /* Preset parameter values based on the mode. */ - switch (kasan_arg_mode) { - case KASAN_ARG_MODE_DEFAULT: - /* Shouldn't happen as per the check above. */ - WARN_ON(1); - return; - case KASAN_ARG_MODE_OFF: - /* If KASAN is disabled, do nothing. */ + /* If KASAN is disabled via command line, don't initialize it. */ + if (kasan_arg == KASAN_ARG_OFF) return; - case KASAN_ARG_MODE_PROD: - static_branch_enable(&kasan_flag_enabled); - break; - case KASAN_ARG_MODE_FULL: - static_branch_enable(&kasan_flag_enabled); - static_branch_enable(&kasan_flag_stacktrace); - break; - } - /* Now, optionally override the presets. */ + /* Enable KASAN. */ + static_branch_enable(&kasan_flag_enabled); switch (kasan_arg_stacktrace) { case KASAN_ARG_STACKTRACE_DEFAULT: + /* + * Default to enabling stack trace collection for + * debug kernels. + */ + if (IS_ENABLED(CONFIG_DEBUG_KERNEL)) + static_branch_enable(&kasan_flag_stacktrace); break; case KASAN_ARG_STACKTRACE_OFF: - static_branch_disable(&kasan_flag_stacktrace); + /* Do nothing, kasan_flag_stacktrace keeps its default value. */ break; case KASAN_ARG_STACKTRACE_ON: static_branch_enable(&kasan_flag_stacktrace); @@ -169,11 +151,16 @@ void __init kasan_init_hw_tags(void) switch (kasan_arg_fault) { case KASAN_ARG_FAULT_DEFAULT: + /* + * Default to no panic on report. + * Do nothing, kasan_flag_panic keeps its default value. + */ break; case KASAN_ARG_FAULT_REPORT: - kasan_flag_panic = false; + /* Do nothing, kasan_flag_panic keeps its default value. */ break; case KASAN_ARG_FAULT_PANIC: + /* Enable panic on report. */ kasan_flag_panic = true; break; } -- 2.30.0.284.gd98b1dd5eaa7-goog
