linux-kernel - [PATCH -fixes v2 2/4] riscv: Fix config KASAN && SPARSEMEM && !SPARSE

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Date:   Mon, 21 Feb 2022 17:12:30 +0100
From:   Alexandre Ghiti <alexandre.ghiti@...onical.com>
To:     Paul Walmsley <paul.walmsley@...ive.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Albert Ou <aou@...s.berkeley.edu>,
        Andrey Ryabinin <ryabinin.a.a@...il.com>,
        Alexander Potapenko <glider@...gle.com>,
        Andrey Konovalov <andreyknvl@...il.com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Alexandre Ghiti <alexandre.ghiti@...onical.com>,
        Aleksandr Nogikh <nogikh@...gle.com>,
        Nick Hu <nickhu@...estech.com>,
        linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org,
        kasan-dev@...glegroups.com
Subject: [PATCH -fixes v2 2/4] riscv: Fix config KASAN && SPARSEMEM && !SPARSE_VMEMMAP

In order to get the pfn of a struct page* when sparsemem is enabled
without vmemmap, the mem_section structures need to be initialized which
happens in sparse_init.

But kasan_early_init calls pfn_to_page way before sparse_init is called,
which then tries to dereference a null mem_section pointer.

Fix this by removing the usage of this function in kasan_early_init.

Fixes: 8ad8b72721d0 ("riscv: Add KASAN support")
Signed-off-by: Alexandre Ghiti <alexandre.ghiti@...onical.com>
---
 arch/riscv/mm/kasan_init.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/arch/riscv/mm/kasan_init.c b/arch/riscv/mm/kasan_init.c
index f61f7ca6fe0f..85e849318389 100644
--- a/arch/riscv/mm/kasan_init.c
+++ b/arch/riscv/mm/kasan_init.c
@@ -202,8 +202,7 @@ asmlinkage void __init kasan_early_init(void)
 
 	for (i = 0; i < PTRS_PER_PTE; ++i)
 		set_pte(kasan_early_shadow_pte + i,
-			mk_pte(virt_to_page(kasan_early_shadow_page),
-			       PAGE_KERNEL));
+			pfn_pte(virt_to_pfn(kasan_early_shadow_page), PAGE_KERNEL));
 
 	for (i = 0; i < PTRS_PER_PMD; ++i)
 		set_pmd(kasan_early_shadow_pmd + i,
-- 
2.32.0