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Date: Tue, 13 Jul 2021 09:19:17 +0200
From: Marco Elver <elver@...gle.com>
To: Woody Lin <woodylin@...gle.com>
Cc: Andrey Ryabinin <ryabinin.a.a@...il.com>,
Dmitry Vyukov <dvyukov@...gle.com>,
Alexander Potapenko <glider@...gle.com>,
Andrey Konovalov <andreyknvl@...il.com>,
Jonathan Corbet <corbet@....net>,
Andrew Morton <akpm@...ux-foundation.org>,
kasan-dev@...glegroups.com, linux-doc@...r.kernel.org,
linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCH v2] mm/kasan: move kasan.fault to mm/kasan/report.c
On Tue, 13 Jul 2021 at 03:07, Woody Lin <woodylin@...gle.com> wrote:
> Move the boot parameter 'kasan.fault' from hw_tags.c to report.c, so it
> can support all KASAN modes - generic, and both tag-based.
>
> Signed-off-by: Woody Lin <woodylin@...gle.com>
Reviewed-by: Marco Elver <elver@...gle.com>
Thank you.
> ---
> Documentation/dev-tools/kasan.rst | 13 ++++++----
> mm/kasan/hw_tags.c | 43 -------------------------------
> mm/kasan/kasan.h | 1 -
> mm/kasan/report.c | 29 ++++++++++++++++++---
> 4 files changed, 34 insertions(+), 52 deletions(-)
>
> diff --git a/Documentation/dev-tools/kasan.rst b/Documentation/dev-tools/kasan.rst
> index 83ec4a556c19..21dc03bc10a4 100644
> --- a/Documentation/dev-tools/kasan.rst
> +++ b/Documentation/dev-tools/kasan.rst
> @@ -181,9 +181,16 @@ By default, KASAN prints a bug report only for the first invalid memory access.
> With ``kasan_multi_shot``, KASAN prints a report on every invalid access. This
> effectively disables ``panic_on_warn`` for KASAN reports.
>
> +Alternatively, independent of ``panic_on_warn`` the ``kasan.fault=`` boot
> +parameter can be used to control panic and reporting behaviour:
> +
> +- ``kasan.fault=report`` or ``=panic`` controls whether to only print a KASAN
> + report or also panic the kernel (default: ``report``). The panic happens even
> + if ``kasan_multi_shot`` is enabled.
> +
> Hardware tag-based KASAN mode (see the section about various modes below) is
> intended for use in production as a security mitigation. Therefore, it supports
> -boot parameters that allow disabling KASAN or controlling its features.
> +additional boot parameters that allow disabling KASAN or controlling features:
>
> - ``kasan=off`` or ``=on`` controls whether KASAN is enabled (default: ``on``).
>
> @@ -199,10 +206,6 @@ boot parameters that allow disabling KASAN or controlling its features.
> - ``kasan.stacktrace=off`` or ``=on`` disables or enables alloc and free stack
> traces collection (default: ``on``).
>
> -- ``kasan.fault=report`` or ``=panic`` controls whether to only print a KASAN
> - report or also panic the kernel (default: ``report``). The panic happens even
> - if ``kasan_multi_shot`` is enabled.
> -
> Implementation details
> ----------------------
>
> diff --git a/mm/kasan/hw_tags.c b/mm/kasan/hw_tags.c
> index 4ea8c368b5b8..51903639e55f 100644
> --- a/mm/kasan/hw_tags.c
> +++ b/mm/kasan/hw_tags.c
> @@ -37,16 +37,9 @@ enum kasan_arg_stacktrace {
> KASAN_ARG_STACKTRACE_ON,
> };
>
> -enum kasan_arg_fault {
> - KASAN_ARG_FAULT_DEFAULT,
> - KASAN_ARG_FAULT_REPORT,
> - KASAN_ARG_FAULT_PANIC,
> -};
> -
> static enum kasan_arg kasan_arg __ro_after_init;
> static enum kasan_arg_mode kasan_arg_mode __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;
>
> /* Whether KASAN is enabled at all. */
> DEFINE_STATIC_KEY_FALSE(kasan_flag_enabled);
> @@ -59,9 +52,6 @@ EXPORT_SYMBOL_GPL(kasan_flag_async);
> /* Whether to collect alloc/free stack traces. */
> DEFINE_STATIC_KEY_FALSE(kasan_flag_stacktrace);
>
> -/* Whether to panic or print a report and disable tag checking on fault. */
> -bool kasan_flag_panic __ro_after_init;
> -
> /* kasan=off/on */
> static int __init early_kasan_flag(char *arg)
> {
> @@ -113,23 +103,6 @@ static int __init early_kasan_flag_stacktrace(char *arg)
> }
> early_param("kasan.stacktrace", early_kasan_flag_stacktrace);
>
> -/* kasan.fault=report/panic */
> -static int __init early_kasan_fault(char *arg)
> -{
> - if (!arg)
> - return -EINVAL;
> -
> - if (!strcmp(arg, "report"))
> - kasan_arg_fault = KASAN_ARG_FAULT_REPORT;
> - else if (!strcmp(arg, "panic"))
> - kasan_arg_fault = KASAN_ARG_FAULT_PANIC;
> - else
> - return -EINVAL;
> -
> - return 0;
> -}
> -early_param("kasan.fault", early_kasan_fault);
> -
> /* kasan_init_hw_tags_cpu() is called for each CPU. */
> void kasan_init_hw_tags_cpu(void)
> {
> @@ -197,22 +170,6 @@ void __init kasan_init_hw_tags(void)
> break;
> }
>
> - 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:
> - /* Do nothing, kasan_flag_panic keeps its default value. */
> - break;
> - case KASAN_ARG_FAULT_PANIC:
> - /* Enable panic on report. */
> - kasan_flag_panic = true;
> - break;
> - }
> -
> pr_info("KernelAddressSanitizer initialized\n");
> }
>
> diff --git a/mm/kasan/kasan.h b/mm/kasan/kasan.h
> index 98e3059bfea4..9d57383ce1fa 100644
> --- a/mm/kasan/kasan.h
> +++ b/mm/kasan/kasan.h
> @@ -36,7 +36,6 @@ static inline bool kasan_async_mode_enabled(void)
>
> #endif
>
> -extern bool kasan_flag_panic __ro_after_init;
> extern bool kasan_flag_async __ro_after_init;
>
> #if defined(CONFIG_KASAN_GENERIC) || defined(CONFIG_KASAN_SW_TAGS)
> diff --git a/mm/kasan/report.c b/mm/kasan/report.c
> index 8fff1825b22c..884a950c7026 100644
> --- a/mm/kasan/report.c
> +++ b/mm/kasan/report.c
> @@ -39,6 +39,31 @@ static unsigned long kasan_flags;
> #define KASAN_BIT_REPORTED 0
> #define KASAN_BIT_MULTI_SHOT 1
>
> +enum kasan_arg_fault {
> + KASAN_ARG_FAULT_DEFAULT,
> + KASAN_ARG_FAULT_REPORT,
> + KASAN_ARG_FAULT_PANIC,
> +};
> +
> +static enum kasan_arg_fault kasan_arg_fault __ro_after_init = KASAN_ARG_FAULT_DEFAULT;
> +
> +/* kasan.fault=report/panic */
> +static int __init early_kasan_fault(char *arg)
> +{
> + if (!arg)
> + return -EINVAL;
> +
> + if (!strcmp(arg, "report"))
> + kasan_arg_fault = KASAN_ARG_FAULT_REPORT;
> + else if (!strcmp(arg, "panic"))
> + kasan_arg_fault = KASAN_ARG_FAULT_PANIC;
> + else
> + return -EINVAL;
> +
> + return 0;
> +}
> +early_param("kasan.fault", early_kasan_fault);
> +
> bool kasan_save_enable_multi_shot(void)
> {
> return test_and_set_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags);
> @@ -102,10 +127,8 @@ static void end_report(unsigned long *flags, unsigned long addr)
> panic_on_warn = 0;
> panic("panic_on_warn set ...\n");
> }
> -#ifdef CONFIG_KASAN_HW_TAGS
> - if (kasan_flag_panic)
> + if (kasan_arg_fault == KASAN_ARG_FAULT_PANIC)
> panic("kasan.fault=panic set ...\n");
> -#endif
> kasan_enable_current();
> }
>
> --
> 2.32.0.93.g670b81a890-goog
>
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