linux-kernel - [PATCH mm v4 36/39] kasan: allow enabling KASAN_VMALLOC and SW/HW

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Message-Id: <d391829df65888170df24e4577f7f0211db808c7.1640036051.git.andreyknvl@google.com>
Date:   Mon, 20 Dec 2021 23:03:30 +0100
From:   andrey.konovalov@...ux.dev
To:     Marco Elver <elver@...gle.com>,
        Alexander Potapenko <glider@...gle.com>,
        Andrew Morton <akpm@...ux-foundation.org>
Cc:     Andrey Konovalov <andreyknvl@...il.com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Andrey Ryabinin <ryabinin.a.a@...il.com>,
        kasan-dev@...glegroups.com, linux-mm@...ck.org,
        Vincenzo Frascino <vincenzo.frascino@....com>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        linux-arm-kernel@...ts.infradead.org,
        Peter Collingbourne <pcc@...gle.com>,
        Evgenii Stepanov <eugenis@...gle.com>,
        linux-kernel@...r.kernel.org,
        Andrey Konovalov <andreyknvl@...gle.com>
Subject: [PATCH mm v4 36/39] kasan: allow enabling KASAN_VMALLOC and SW/HW_TAGS

From: Andrey Konovalov <andreyknvl@...gle.com>

Allow enabling CONFIG_KASAN_VMALLOC with SW_TAGS and HW_TAGS KASAN
modes.

Also adjust CONFIG_KASAN_VMALLOC description:

- Mention HW_TAGS support.
- Remove unneeded internal details: they have no place in Kconfig
  description and are already explained in the documentation.

Signed-off-by: Andrey Konovalov <andreyknvl@...gle.com>
---
 lib/Kconfig.kasan | 20 ++++++++++----------
 1 file changed, 10 insertions(+), 10 deletions(-)

diff --git a/lib/Kconfig.kasan b/lib/Kconfig.kasan
index 879757b6dd14..1f3e620188a2 100644
--- a/lib/Kconfig.kasan
+++ b/lib/Kconfig.kasan
@@ -178,17 +178,17 @@ config KASAN_TAGS_IDENTIFY
 	  memory consumption.
 
 config KASAN_VMALLOC
-	bool "Back mappings in vmalloc space with real shadow memory"
-	depends on KASAN_GENERIC && HAVE_ARCH_KASAN_VMALLOC
+	bool "Check accesses to vmalloc allocations"
+	depends on HAVE_ARCH_KASAN_VMALLOC
 	help
-	  By default, the shadow region for vmalloc space is the read-only
-	  zero page. This means that KASAN cannot detect errors involving
-	  vmalloc space.
-
-	  Enabling this option will hook in to vmap/vmalloc and back those
-	  mappings with real shadow memory allocated on demand. This allows
-	  for KASAN to detect more sorts of errors (and to support vmapped
-	  stacks), but at the cost of higher memory usage.
+	  This mode makes KASAN check accesses to vmalloc allocations for
+	  validity.
+
+	  With software KASAN modes, checking is done for all types of vmalloc
+	  allocations. Enabling this option leads to higher memory usage.
+
+	  With hardware tag-based KASAN, only VM_ALLOC mappings are checked.
+	  There is no additional memory usage.
 
 config KASAN_KUNIT_TEST
 	tristate "KUnit-compatible tests of KASAN bug detection capabilities" if !KUNIT_ALL_TESTS
-- 
2.25.1