[v5] mm/kasan: make kasan=on|off work for all three modes

[PATCH v5 14/15] mm/kasan: add document into kernel-parameters.txt

Posted by Baoquan He 1 month, 1 week ago

And also remove the relevant description in dev-tools/kasan.rst
which is hw_tags specificially.

Signed-off-by: Baoquan He <bhe@redhat.com>
---
 Documentation/admin-guide/kernel-parameters.txt | 4 ++++
 Documentation/dev-tools/kasan.rst               | 2 --
 2 files changed, 4 insertions(+), 2 deletions(-)

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index cb850e5290c2..e0115fad9e60 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -2899,6 +2899,10 @@ Kernel parameters
 	js=		[HW,JOY] Analog joystick
 			See Documentation/input/joydev/joystick.rst.
 
+	kasan=		[KNL] controls whether KASAN is enabled.
+			Format: off | on
+			default: on
+
 	kasan_multi_shot
 			[KNL] Enforce KASAN (Kernel Address Sanitizer) to print
 			report on every invalid memory access. Without this
diff --git a/Documentation/dev-tools/kasan.rst b/Documentation/dev-tools/kasan.rst
index a034700da7c4..eaae83fcb5e4 100644
--- a/Documentation/dev-tools/kasan.rst
+++ b/Documentation/dev-tools/kasan.rst
@@ -129,8 +129,6 @@ Hardware Tag-Based KASAN mode is intended for use in production as a security
 mitigation. Therefore, it supports additional boot parameters that allow
 disabling KASAN altogether or controlling its features:
 
-- ``kasan=off`` or ``=on`` controls whether KASAN is enabled (default: ``on``).
-
 - ``kasan.mode=sync``, ``=async`` or ``=asymm`` controls whether KASAN
   is configured in synchronous, asynchronous or asymmetric mode of
   execution (default: ``sync``).
-- 
2.52.0

Re: [PATCH v5 14/15] mm/kasan: add document into kernel-parameters.txt

Posted by Samuel Holland 3 weeks, 4 days ago

Hi Baoquan,

On 2026-02-25 2:14 AM, Baoquan He wrote:
> And also remove the relevant description in dev-tools/kasan.rst
> which is hw_tags specificially.
> 
> Signed-off-by: Baoquan He <bhe@redhat.com>
> ---
>  Documentation/admin-guide/kernel-parameters.txt | 4 ++++
>  Documentation/dev-tools/kasan.rst               | 2 --
>  2 files changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
> index cb850e5290c2..e0115fad9e60 100644
> --- a/Documentation/admin-guide/kernel-parameters.txt
> +++ b/Documentation/admin-guide/kernel-parameters.txt
> @@ -2899,6 +2899,10 @@ Kernel parameters
>  	js=		[HW,JOY] Analog joystick
>  			See Documentation/input/joydev/joystick.rst.
>  
> +	kasan=		[KNL] controls whether KASAN is enabled.
> +			Format: off | on
> +			default: on
> +
>  	kasan_multi_shot
>  			[KNL] Enforce KASAN (Kernel Address Sanitizer) to print
>  			report on every invalid memory access. Without this
> diff --git a/Documentation/dev-tools/kasan.rst b/Documentation/dev-tools/kasan.rst
> index a034700da7c4..eaae83fcb5e4 100644
> --- a/Documentation/dev-tools/kasan.rst
> +++ b/Documentation/dev-tools/kasan.rst
> @@ -129,8 +129,6 @@ Hardware Tag-Based KASAN mode is intended for use in production as a security
>  mitigation. Therefore, it supports additional boot parameters that allow
>  disabling KASAN altogether or controlling its features:

The sentence above is now incorrect as well. I would recommend documenting the
parameter earlier in the "Boot parameters" section instead of removing it from
this document entirely.

Regards,
Samuel

>  
> -- ``kasan=off`` or ``=on`` controls whether KASAN is enabled (default: ``on``).
> -
>  - ``kasan.mode=sync``, ``=async`` or ``=asymm`` controls whether KASAN
>    is configured in synchronous, asynchronous or asymmetric mode of
>    execution (default: ``sync``).

Re: [PATCH v5 14/15] mm/kasan: add document into kernel-parameters.txt

Posted by Baoquan He 3 weeks ago

On 03/12/26 at 07:53am, Samuel Holland wrote:
> Hi Baoquan,
> 
> On 2026-02-25 2:14 AM, Baoquan He wrote:
> > And also remove the relevant description in dev-tools/kasan.rst
> > which is hw_tags specificially.
> > 
> > Signed-off-by: Baoquan He <bhe@redhat.com>
> > ---
> >  Documentation/admin-guide/kernel-parameters.txt | 4 ++++
> >  Documentation/dev-tools/kasan.rst               | 2 --
> >  2 files changed, 4 insertions(+), 2 deletions(-)
> > 
> > diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
> > index cb850e5290c2..e0115fad9e60 100644
> > --- a/Documentation/admin-guide/kernel-parameters.txt
> > +++ b/Documentation/admin-guide/kernel-parameters.txt
> > @@ -2899,6 +2899,10 @@ Kernel parameters
> >  	js=		[HW,JOY] Analog joystick
> >  			See Documentation/input/joydev/joystick.rst.
> >  
> > +	kasan=		[KNL] controls whether KASAN is enabled.
> > +			Format: off | on
> > +			default: on
> > +
> >  	kasan_multi_shot
> >  			[KNL] Enforce KASAN (Kernel Address Sanitizer) to print
> >  			report on every invalid memory access. Without this
> > diff --git a/Documentation/dev-tools/kasan.rst b/Documentation/dev-tools/kasan.rst
> > index a034700da7c4..eaae83fcb5e4 100644
> > --- a/Documentation/dev-tools/kasan.rst
> > +++ b/Documentation/dev-tools/kasan.rst
> > @@ -129,8 +129,6 @@ Hardware Tag-Based KASAN mode is intended for use in production as a security
> >  mitigation. Therefore, it supports additional boot parameters that allow
> >  disabling KASAN altogether or controlling its features:
> 
> The sentence above is now incorrect as well. I would recommend documenting the
> parameter earlier in the "Boot parameters" section instead of removing it from
> this document entirely.

Good catch and the suggestion is good to me. Thanks.

Is below change OK to you?


From 317be48b9c1bf9d33b8d8fff5e401e3155531d81 Mon Sep 17 00:00:00 2001
From: Baoquan He <bhe@redhat.com>
Date: Tue, 17 Mar 2026 11:28:39 +0800
Subject: [PATCH] mm/kasan: adjust documentation
Content-type: text/plain

To reflect the change of kasan=on|off.

Signed-off-by: Baoquan He <bhe@redhat.com>
---
 Documentation/dev-tools/kasan.rst | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/Documentation/dev-tools/kasan.rst b/Documentation/dev-tools/kasan.rst
index a034700da7c4..8e65bc04dbcd 100644
--- a/Documentation/dev-tools/kasan.rst
+++ b/Documentation/dev-tools/kasan.rst
@@ -103,6 +103,9 @@ Boot parameters
 KASAN is affected by the generic ``panic_on_warn`` command line parameter.
 When it is enabled, KASAN panics the kernel after printing a bug report.
 
+The generic ``kasan=off`` or ``=on`` command line parameter controls
+whether KASAN is enabled (default: ``on``).
+
 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.
@@ -127,9 +130,7 @@ modes below) support altering stack trace collection behavior:
 
 Hardware Tag-Based KASAN mode is intended for use in production as a security
 mitigation. Therefore, it supports additional boot parameters that allow
-disabling KASAN altogether or controlling its features:
-
-- ``kasan=off`` or ``=on`` controls whether KASAN is enabled (default: ``on``).
+controlling its features:
 
 - ``kasan.mode=sync``, ``=async`` or ``=asymm`` controls whether KASAN
   is configured in synchronous, asynchronous or asymmetric mode of
-- 
2.52.0

Re: [PATCH v5 14/15] mm/kasan: add document into kernel-parameters.txt

Posted by Samuel Holland 3 weeks ago

On 2026-03-16 10:36 PM, Baoquan He wrote:
> On 03/12/26 at 07:53am, Samuel Holland wrote:
>> Hi Baoquan,
>>
>> On 2026-02-25 2:14 AM, Baoquan He wrote:
>>> And also remove the relevant description in dev-tools/kasan.rst
>>> which is hw_tags specificially.
>>>
>>> Signed-off-by: Baoquan He <bhe@redhat.com>
>>> ---
>>>  Documentation/admin-guide/kernel-parameters.txt | 4 ++++
>>>  Documentation/dev-tools/kasan.rst               | 2 --
>>>  2 files changed, 4 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
>>> index cb850e5290c2..e0115fad9e60 100644
>>> --- a/Documentation/admin-guide/kernel-parameters.txt
>>> +++ b/Documentation/admin-guide/kernel-parameters.txt
>>> @@ -2899,6 +2899,10 @@ Kernel parameters
>>>  	js=		[HW,JOY] Analog joystick
>>>  			See Documentation/input/joydev/joystick.rst.
>>>  
>>> +	kasan=		[KNL] controls whether KASAN is enabled.
>>> +			Format: off | on
>>> +			default: on
>>> +
>>>  	kasan_multi_shot
>>>  			[KNL] Enforce KASAN (Kernel Address Sanitizer) to print
>>>  			report on every invalid memory access. Without this
>>> diff --git a/Documentation/dev-tools/kasan.rst b/Documentation/dev-tools/kasan.rst
>>> index a034700da7c4..eaae83fcb5e4 100644
>>> --- a/Documentation/dev-tools/kasan.rst
>>> +++ b/Documentation/dev-tools/kasan.rst
>>> @@ -129,8 +129,6 @@ Hardware Tag-Based KASAN mode is intended for use in production as a security
>>>  mitigation. Therefore, it supports additional boot parameters that allow
>>>  disabling KASAN altogether or controlling its features:
>>
>> The sentence above is now incorrect as well. I would recommend documenting the
>> parameter earlier in the "Boot parameters" section instead of removing it from
>> this document entirely.
> 
> Good catch and the suggestion is good to me. Thanks.
> 
> Is below change OK to you?
> 
> 
> From 317be48b9c1bf9d33b8d8fff5e401e3155531d81 Mon Sep 17 00:00:00 2001
> From: Baoquan He <bhe@redhat.com>
> Date: Tue, 17 Mar 2026 11:28:39 +0800
> Subject: [PATCH] mm/kasan: adjust documentation

I'd suggest something a bit more specific, maybe like "mm/kasan: document kasan=
for all modes".

> Content-type: text/plain
> 
> To reflect the change of kasan=on|off.
> 
> Signed-off-by: Baoquan He <bhe@redhat.com>
> ---
>  Documentation/dev-tools/kasan.rst | 7 ++++---
>  1 file changed, 4 insertions(+), 3 deletions(-)
> 
> diff --git a/Documentation/dev-tools/kasan.rst b/Documentation/dev-tools/kasan.rst
> index a034700da7c4..8e65bc04dbcd 100644
> --- a/Documentation/dev-tools/kasan.rst
> +++ b/Documentation/dev-tools/kasan.rst
> @@ -103,6 +103,9 @@ Boot parameters
>  KASAN is affected by the generic ``panic_on_warn`` command line parameter.
>  When it is enabled, KASAN panics the kernel after printing a bug report.
>  
> +The generic ``kasan=off`` or ``=on`` command line parameter controls
> +whether KASAN is enabled (default: ``on``).
> +

This is in the middle of paragraphs describing the fault reporting options. I'd
suggest to move it to the beginning of the section.

With those fixes, you can add

Reviewed-by: Samuel Holland <samuel.holland@sifive.com>

>  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.
> @@ -127,9 +130,7 @@ modes below) support altering stack trace collection behavior:
>  
>  Hardware Tag-Based KASAN mode is intended for use in production as a security
>  mitigation. Therefore, it supports additional boot parameters that allow
> -disabling KASAN altogether or controlling its features:
> -
> -- ``kasan=off`` or ``=on`` controls whether KASAN is enabled (default: ``on``).
> +controlling its features:
>  
>  - ``kasan.mode=sync``, ``=async`` or ``=asymm`` controls whether KASAN
>    is configured in synchronous, asynchronous or asymmetric mode of