From 4606bbb6b19ccaa74159e1f3628e8a2414557167 Mon Sep 17 00:00:00 2001
From: Alexandre Ghiti <alexandre.ghiti@canonical.com>
Date: Fri, 29 Oct 2021 06:59:26 +0200
Subject: [PATCH] riscv: Do not re-populate shadow memory with kasan_populate_early_shadow
Git-commit: cf11d01135ea1ff7fddb612033e3cb5cde279ff2
Patch-mainline: v5.15
References: stable-5.14.16

commit cf11d01135ea1ff7fddb612033e3cb5cde279ff2 upstream.

When calling this function, all the shadow memory is already populated
with kasan_early_shadow_pte which has PAGE_KERNEL protection.
kasan_populate_early_shadow write-protects the mapping of the range
of addresses passed in argument in zero_pte_populate, which actually
write-protects all the shadow memory mapping since kasan_early_shadow_pte
is used for all the shadow memory at this point. And then when using
memblock API to populate the shadow memory, the first write access to the
kernel stack triggers a trap. This becomes visible with the next commit
that contains a fix for asan-stack.

We already manually populate all the shadow memory in kasan_early_init
and we write-protect kasan_early_shadow_pte at the end of kasan_init
which makes the calls to kasan_populate_early_shadow superfluous so
we can remove them.

Signed-off-by: Alexandre Ghiti <alexandre.ghiti@canonical.com>
Fixes: e178d670f251 ("riscv/kasan: add KASAN_VMALLOC support")
Fixes: 8ad8b72721d0 ("riscv: Add KASAN support")
Cc: stable@vger.kernel.org
Signed-off-by: Palmer Dabbelt <palmerdabbelt@google.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Acked-by: Takashi Iwai <tiwai@suse.de>

---
 arch/riscv/mm/kasan_init.c | 11 -----------
 1 file changed, 11 deletions(-)

diff --git a/arch/riscv/mm/kasan_init.c b/arch/riscv/mm/kasan_init.c
index d7189c8714a9..89a8376ce44e 100644
--- a/arch/riscv/mm/kasan_init.c
+++ b/arch/riscv/mm/kasan_init.c
@@ -172,21 +172,10 @@ void __init kasan_init(void)
 	phys_addr_t p_start, p_end;
 	u64 i;
 
-	/*
-	 * Populate all kernel virtual address space with kasan_early_shadow_page
-	 * except for the linear mapping and the modules/kernel/BPF mapping.
-	 */
-	kasan_populate_early_shadow((void *)KASAN_SHADOW_START,
-				    (void *)kasan_mem_to_shadow((void *)
-								VMEMMAP_END));
 	if (IS_ENABLED(CONFIG_KASAN_VMALLOC))
 		kasan_shallow_populate(
 			(void *)kasan_mem_to_shadow((void *)VMALLOC_START),
 			(void *)kasan_mem_to_shadow((void *)VMALLOC_END));
-	else
-		kasan_populate_early_shadow(
-			(void *)kasan_mem_to_shadow((void *)VMALLOC_START),
-			(void *)kasan_mem_to_shadow((void *)VMALLOC_END));
 
 	/* Populate the linear mapping */
 	for_each_mem_range(i, &p_start, &p_end) {
-- 
2.26.2