Commit 9a0732ef authored Mar 24, 2021 by Lecopzer Chen Committed by Catalin Marinas Mar 29, 2021

arm64: kasan: don't populate vmalloc area for CONFIG_KASAN_VMALLOC



Linux support KAsan for VMALLOC since commit 3c5c3cfb
("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 zero shadow at init
VMALLOC_VADDR: backed with zero shadow at init

After:

MODULE_VADDR: no mapping, no zero shadow at init
VMALLOC_VADDR: no mapping, no zero 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@mediatek.com>
Acked-by: Andrey Konovalov <andreyknvl@gmail.com>
Tested-by: Andrey Konovalov <andreyknvl@gmail.com>
Tested-by: Ard Biesheuvel <ardb@kernel.org>
Link: https://lore.kernel.org/r/20210324040522.15548-2-lecopzer.chen@mediatek.com


[catalin.marinas@arm.com: add a build check on VMALLOC_START != MODULES_END]
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

parent 1e28eed1

arch/arm64/mm/kasan_init.c

+14 −5

Original line number	Diff line number	Diff line
		@@ -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 +244,18 @@ static void __init kasan_init_shadow(void)

		kasan_populate_early_shadow(kasan_mem_to_shadow((void *)PAGE_END),
		(void *)mod_shadow_start);

		if (IS_ENABLED(CONFIG_KASAN_VMALLOC)) {
		BUILD_BUG_ON(VMALLOC_START != MODULES_END);
		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);