[PATCH] powerpc/kasan: Fix CONFIG_KASAN_VMALLOC for 8xx

[PATCH] powerpc/kasan: Fix CONFIG_KASAN_VMALLOC for 8xx

[Christophe Leroy]

Before the commit identified below, pages tables allocation was
performed after the allocation of final shadow area for linear memory.
But that commit switched the order, leading to page tables being
already allocated at the time 8xx kasan_init_shadow_8M() is called.
Due to this, kasan_init_shadow_8M() doesn't map the needed
shadow entries because there are already page tables.

kasan_init_shadow_8M() installs huge PMD entries instead of page
tables. We could at that time free the page tables, but there is no
point in creating page tables that get freed before being used.

Only book3s/32 hash needs early allocation of page tables. For other
variants, we can keep the initial order and create remaining page
tables after the allocation of final shadow memory for linear mem.

Move back the allocation of shadow page tables for
CONFIG_KASAN_VMALLOC into kasan_init() after the loop which creates
final shadow memory for linear mem.

Fixes: 41ea93cf7ba4 ("powerpc/kasan: Fix shadow pages allocation failure")
Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
---
 arch/powerpc/mm/kasan/kasan_init_32.c | 12 +++++++++---
 1 file changed, 9 insertions(+), 3 deletions(-)

diff --git a/arch/powerpc/mm/kasan/kasan_init_32.c b/arch/powerpc/mm/kasan/kasan_init_32.c
index fb294046e00e..929716ea21e9 100644
--- a/arch/powerpc/mm/kasan/kasan_init_32.c
+++ b/arch/powerpc/mm/kasan/kasan_init_32.c
@@ -127,8 +127,7 @@ void __init kasan_mmu_init(void)
 {
 	int ret;
 
-	if (early_mmu_has_feature(MMU_FTR_HPTE_TABLE) ||
-	    IS_ENABLED(CONFIG_KASAN_VMALLOC)) {
+	if (early_mmu_has_feature(MMU_FTR_HPTE_TABLE)) {
 		ret = kasan_init_shadow_page_tables(KASAN_SHADOW_START, KASAN_SHADOW_END);
 
 		if (ret)
@@ -139,11 +138,11 @@ void __init kasan_mmu_init(void)
 void __init kasan_init(void)
 {
 	struct memblock_region *reg;
+	int ret;
 
 	for_each_memblock(memory, reg) {
 		phys_addr_t base = reg->base;
 		phys_addr_t top = min(base + reg->size, total_lowmem);
-		int ret;
 
 		if (base >= top)
 			continue;
@@ -153,6 +152,13 @@ void __init kasan_init(void)
 			panic("kasan: kasan_init_region() failed");
 	}
 
+	if (IS_ENABLED(CONFIG_KASAN_VMALLOC)) {
+		ret = kasan_init_shadow_page_tables(KASAN_SHADOW_START, KASAN_SHADOW_END);
+
+		if (ret)
+			panic("kasan: kasan_init_shadow_page_tables() failed");
+	}
+
 	kasan_remap_early_shadow_ro();
 
 	clear_page(kasan_early_shadow_page);
-- 
2.25.0

Re: [PATCH] powerpc/kasan: Fix CONFIG_KASAN_VMALLOC for 8xx

[Michael Ellerman]

On Fri, 11 Sep 2020 05:05:38 +0000 (UTC), Christophe Leroy wrote:
> Before the commit identified below, pages tables allocation was
> performed after the allocation of final shadow area for linear memory.
> But that commit switched the order, leading to page tables being
> already allocated at the time 8xx kasan_init_shadow_8M() is called.
> Due to this, kasan_init_shadow_8M() doesn't map the needed
> shadow entries because there are already page tables.
> 
> [...]

Applied to powerpc/next.

[1/1] powerpc/kasan: Fix CONFIG_KASAN_VMALLOC for 8xx
      https://git.kernel.org/powerpc/c/4c42dc5c69a8f24c467a6c997909d2f1d4efdc7f

cheers