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* [PATCH] mm/kasan: move kasan.fault to mm/kasan/report.c
@ 2021-07-12 15:16 Woody Lin
  2021-07-12 16:44 ` Marco Elver
  0 siblings, 1 reply; 2+ messages in thread
From: Woody Lin @ 2021-07-12 15:16 UTC (permalink / raw)
  To: Andrey Ryabinin, Dmitry Vyukov
  Cc: Alexander Potapenko, Andrey Konovalov, Jonathan Corbet,
	Andrew Morton, kasan-dev, linux-doc, linux-kernel, linux-mm,
	Woody Lin

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@google.com>
---
 Documentation/dev-tools/kasan.rst |  2 ++
 mm/kasan/hw_tags.c                | 43 -------------------------------
 mm/kasan/report.c                 | 29 ++++++++++++++++++---
 3 files changed, 28 insertions(+), 46 deletions(-)

diff --git a/Documentation/dev-tools/kasan.rst b/Documentation/dev-tools/kasan.rst
index 83ec4a556c19..ab8e27d45632 100644
--- a/Documentation/dev-tools/kasan.rst
+++ b/Documentation/dev-tools/kasan.rst
@@ -203,6 +203,8 @@ boot parameters that allow disabling KASAN or controlling its features.
   report or also panic the kernel (default: ``report``). The panic happens even
   if ``kasan_multi_shot`` is enabled.
 
+  Note: The boot parameter 'kasan.fault' is supported by all KASAN modes.
+
 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/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


^ permalink raw reply	[flat|nested] 2+ messages in thread

* Re: [PATCH] mm/kasan: move kasan.fault to mm/kasan/report.c
  2021-07-12 15:16 [PATCH] mm/kasan: move kasan.fault to mm/kasan/report.c Woody Lin
@ 2021-07-12 16:44 ` Marco Elver
  0 siblings, 0 replies; 2+ messages in thread
From: Marco Elver @ 2021-07-12 16:44 UTC (permalink / raw)
  To: Woody Lin
  Cc: Andrey Ryabinin, Dmitry Vyukov, Alexander Potapenko,
	Andrey Konovalov, Jonathan Corbet, Andrew Morton, kasan-dev,
	linux-doc, linux-kernel, linux-mm

On Mon, Jul 12, 2021 at 11:16PM +0800, 'Woody Lin' via kasan-dev 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@google.com>
> ---
>  Documentation/dev-tools/kasan.rst |  2 ++
>  mm/kasan/hw_tags.c                | 43 -------------------------------
>  mm/kasan/report.c                 | 29 ++++++++++++++++++---
>  3 files changed, 28 insertions(+), 46 deletions(-)
> 
> diff --git a/Documentation/dev-tools/kasan.rst b/Documentation/dev-tools/kasan.rst
> index 83ec4a556c19..ab8e27d45632 100644
> --- a/Documentation/dev-tools/kasan.rst
> +++ b/Documentation/dev-tools/kasan.rst
> @@ -203,6 +203,8 @@ boot parameters that allow disabling KASAN or controlling its features.
>    report or also panic the kernel (default: ``report``). The panic happens even
>    if ``kasan_multi_shot`` is enabled.
>  
> +  Note: The boot parameter 'kasan.fault' is supported by all KASAN modes.

This documentation change seems hacked on. Could we change it like this:

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
 ----------------------
 

[...]
> -/* Whether to panic or print a report and disable tag checking on fault. */
> -bool kasan_flag_panic __ro_after_init;

There's also an extern declaration in kasan.h, which should be removed.

Thanks,
-- Marco

^ permalink raw reply	[flat|nested] 2+ messages in thread

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