linux-kernel - [PATCH v3 1/5] arm64: kasan: don't populate vmalloc area for CONFIG_KASAN

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Date:   Sat, 6 Feb 2021 16:35:48 +0800
From:   Lecopzer Chen <lecopzer.chen@...iatek.com>
To:     <linux-kernel@...r.kernel.org>, <linux-mm@...ck.org>,
        <kasan-dev@...glegroups.com>,
        <linux-arm-kernel@...ts.infradead.org>, <will@...nel.org>
CC:     <dan.j.williams@...el.com>, <aryabinin@...tuozzo.com>,
        <glider@...gle.com>, <dvyukov@...gle.com>,
        <akpm@...ux-foundation.org>, <linux-mediatek@...ts.infradead.org>,
        <yj.chiang@...iatek.com>, <catalin.marinas@....com>,
        <ardb@...nel.org>, <andreyknvl@...gle.com>, <broonie@...nel.org>,
        <linux@...ck-us.net>, <rppt@...nel.org>,
        <tyhicks@...ux.microsoft.com>, <robin.murphy@....com>,
        <vincenzo.frascino@....com>, <gustavoars@...nel.org>,
        <lecopzer@...il.com>, Lecopzer Chen <lecopzer.chen@...iatek.com>
Subject: [PATCH v3 1/5] arm64: kasan: don't populate vmalloc area for CONFIG_KASAN_VMALLOC

Linux support KAsan for VMALLOC since commit 3c5c3cfb9ef4da9
("kasan: support backing vmalloc space with real shadow memory")

Like how the MODULES_VADDR does now, just not to early populate
the VMALLOC_START between VMALLOC_END.

Before:

MODULE_VADDR: no mapping, no zoreo shadow at init
VMALLOC_VADDR: backed with zero shadow at init

After:

MODULE_VADDR: no mapping, no zoreo shadow at init
VMALLOC_VADDR: no mapping, no zoreo shadow at init

Thus the mapping will get allocated on demand by the core function
of KASAN_VMALLOC.

  -----------  vmalloc_shadow_start
 |           |
 |           |
 |           | <= non-mapping
 |           |
 |           |
 |-----------|
 |///////////|<- kimage shadow with page table mapping.
 |-----------|
 |           |
 |           | <= non-mapping
 |           |
 ------------- vmalloc_shadow_end
 |00000000000|
 |00000000000| <= Zero shadow
 |00000000000|
 ------------- KASAN_SHADOW_END

Signed-off-by: Lecopzer Chen <lecopzer.chen@...iatek.com>
---
 arch/arm64/mm/kasan_init.c | 18 +++++++++++++-----
 1 file changed, 13 insertions(+), 5 deletions(-)

diff --git a/arch/arm64/mm/kasan_init.c b/arch/arm64/mm/kasan_init.c
index d8e66c78440e..20d06008785f 100644
--- a/arch/arm64/mm/kasan_init.c
+++ b/arch/arm64/mm/kasan_init.c
@@ -214,6 +214,7 @@ static void __init kasan_init_shadow(void)
 {
 	u64 kimg_shadow_start, kimg_shadow_end;
 	u64 mod_shadow_start, mod_shadow_end;
+	u64 vmalloc_shadow_end;
 	phys_addr_t pa_start, pa_end;
 	u64 i;
 
@@ -223,6 +224,8 @@ static void __init kasan_init_shadow(void)
 	mod_shadow_start = (u64)kasan_mem_to_shadow((void *)MODULES_VADDR);
 	mod_shadow_end = (u64)kasan_mem_to_shadow((void *)MODULES_END);
 
+	vmalloc_shadow_end = (u64)kasan_mem_to_shadow((void *)VMALLOC_END);
+
 	/*
 	 * We are going to perform proper setup of shadow memory.
 	 * At first we should unmap early shadow (clear_pgds() call below).
@@ -241,12 +244,17 @@ static void __init kasan_init_shadow(void)
 
 	kasan_populate_early_shadow(kasan_mem_to_shadow((void *)PAGE_END),
 				   (void *)mod_shadow_start);
-	kasan_populate_early_shadow((void *)kimg_shadow_end,
-				   (void *)KASAN_SHADOW_END);
 
-	if (kimg_shadow_start > mod_shadow_end)
-		kasan_populate_early_shadow((void *)mod_shadow_end,
-					    (void *)kimg_shadow_start);
+	if (IS_ENABLED(CONFIG_KASAN_VMALLOC))
+		kasan_populate_early_shadow((void *)vmalloc_shadow_end,
+					    (void *)KASAN_SHADOW_END);
+	else {
+		kasan_populate_early_shadow((void *)kimg_shadow_end,
+					    (void *)KASAN_SHADOW_END);
+		if (kimg_shadow_start > mod_shadow_end)
+			kasan_populate_early_shadow((void *)mod_shadow_end,
+						    (void *)kimg_shadow_start);
+	}
 
 	for_each_mem_range(i, &pa_start, &pa_end) {
 		void *start = (void *)__phys_to_virt(pa_start);
-- 
2.25.1