linux-kernel - Re: [PATCH v2 1/2] kasan: Refactor pcpu kasan vmalloc unpoison

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Message-ID: <bi7dif47rpmdymfu3fkuz432vv5p2tmabk5snpqo27f5fitq5x@xap7rkeqejrj>
Date: Wed, 03 Dec 2025 16:43:43 +0000
From: Maciej Wieczór-Retman <m.wieczorretman@...me>
To: Andrey Konovalov <andreyknvl@...il.com>
Cc: Andrey Ryabinin <ryabinin.a.a@...il.com>, Alexander Potapenko <glider@...gle.com>, Dmitry Vyukov <dvyukov@...gle.com>, Vincenzo Frascino <vincenzo.frascino@....com>, Andrew Morton <akpm@...ux-foundation.org>, Uladzislau Rezki <urezki@...il.com>, Marco Elver <elver@...gle.com>, stable@...r.kernel.org, Maciej Wieczor-Retman <maciej.wieczor-retman@...el.com>, kasan-dev@...glegroups.com, linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCH v2 1/2] kasan: Refactor pcpu kasan vmalloc unpoison

On 2025-12-03 at 16:53:04 +0100, Andrey Konovalov wrote:
>On Tue, Dec 2, 2025 at 3:29 PM Maciej Wieczor-Retman
><m.wieczorretman@...me> wrote:
>>
>> From: Maciej Wieczor-Retman <maciej.wieczor-retman@...el.com>
>>
...
>> diff --git a/mm/kasan/common.c b/mm/kasan/common.c
>> index d4c14359feaf..7884ea7d13f9 100644
>> --- a/mm/kasan/common.c
>> +++ b/mm/kasan/common.c
>> @@ -28,6 +28,7 @@
>>  #include <linux/string.h>
>>  #include <linux/types.h>
>>  #include <linux/bug.h>
>> +#include <linux/vmalloc.h>
>>
>>  #include "kasan.h"
>>  #include "../slab.h"
>> @@ -582,3 +583,19 @@ bool __kasan_check_byte(const void *address, unsigned long ip)
>>         }
>>         return true;
>>  }
>> +
>> +#ifdef CONFIG_KASAN_VMALLOC
>> +void kasan_unpoison_vmap_areas(struct vm_struct **vms, int nr_vms,
>> +                              kasan_vmalloc_flags_t flags)
>
>kasan_unpoison_vmap_areas() needs to be defined in
>inclunde/linux/kasan.h and call __kasan_unpoison_vmap_areas() when
>kasan_enabled() == true, similar to the other wrappers.
>
>And check my comment for patch #2: with that, you should not need to
>add so many new __helpers: just __kasan_unpoison_vmalloc and
>__kasan_unpoison_vmap_areas should suffice.

Okay, I think I see what you mean. I was trying to avoid using
__kasan_unpoison_vmalloc() here so that it compiled properly, but that
was before I added the ifdef guard. Now there is not reason not to use
it here.

I'll make the changes you mentioned.

Kind regards
Maciej Wieczór-Retman

>
>> +{
>> +       unsigned long size;
>> +       void *addr;
>> +       int area;
>> +
>> +       for (area = 0 ; area < nr_vms ; area++) {
>> +               size = vms[area]->size;
>> +               addr = vms[area]->addr;
>> +               vms[area]->addr = __kasan_unpoison_vmap_areas(addr, size, flags);
>> +       }
>> +}
>> +#endif