linux-kernel - [PATCH 5.7 341/376] powerpc/32: Disable KASAN with pages bigger than 16k

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Date:   Fri, 19 Jun 2020 16:34:19 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, kbuild test robot <lkp@...el.com>,
        Christophe Leroy <christophe.leroy@...roup.eu>,
        Michael Ellerman <mpe@...erman.id.au>
Subject: [PATCH 5.7 341/376] powerpc/32: Disable KASAN with pages bigger than 16k

From: Christophe Leroy <christophe.leroy@...roup.eu>

commit 888468ce725a4cd56d72dc7e5096078f7a9251a0 upstream.

Mapping of early shadow area is implemented by using a single static
page table having all entries pointing to the same early shadow page.
The shadow area must therefore occupy full PGD entries.

The shadow area has a size of 128MB starting at 0xf8000000.
With 4k pages, a PGD entry is 4MB
With 16k pages, a PGD entry is 64MB
With 64k pages, a PGD entry is 1GB which is too big.

Until we rework the early shadow mapping, disable KASAN when the page
size is too big.

Fixes: 2edb16efc899 ("powerpc/32: Add KASAN support")
Cc: stable@...r.kernel.org # v5.2+
Reported-by: kbuild test robot <lkp@...el.com>
Signed-off-by: Christophe Leroy <christophe.leroy@...roup.eu>
Signed-off-by: Michael Ellerman <mpe@...erman.id.au>
Link: https://lore.kernel.org/r/7195fcde7314ccbf7a081b356084a69d421b10d4.1590660977.git.christophe.leroy@csgroup.eu
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 arch/powerpc/Kconfig |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -170,8 +170,8 @@ config PPC
 	select HAVE_ARCH_AUDITSYSCALL
 	select HAVE_ARCH_HUGE_VMAP		if PPC_BOOK3S_64 && PPC_RADIX_MMU
 	select HAVE_ARCH_JUMP_LABEL
-	select HAVE_ARCH_KASAN			if PPC32
-	select HAVE_ARCH_KASAN_VMALLOC		if PPC32
+	select HAVE_ARCH_KASAN			if PPC32 && PPC_PAGE_SHIFT <= 14
+	select HAVE_ARCH_KASAN_VMALLOC		if PPC32 && PPC_PAGE_SHIFT <= 14
 	select HAVE_ARCH_KGDB
 	select HAVE_ARCH_MMAP_RND_BITS
 	select HAVE_ARCH_MMAP_RND_COMPAT_BITS	if COMPAT