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Message-ID: <CACRpkdYjeqaRzz+hBOGGLEAJn5QmFGof2ysQuVNC_+vV49WPRw@mail.gmail.com>
Date: Tue, 15 Oct 2024 22:55:05 +0200
From: Linus Walleij <linus.walleij@...aro.org>
To: Ard Biesheuvel <ardb@...nel.org>
Cc: Mark Rutland <mark.rutland@....com>, Clement LE GOFFIC <clement.legoffic@...s.st.com>,
Russell King <linux@...linux.org.uk>,
"Russell King (Oracle)" <rmk+kernel@...linux.org.uk>, Kees Cook <kees@...nel.org>,
AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>, Mark Brown <broonie@...nel.org>,
linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
linux-stm32@...md-mailman.stormreply.com,
Antonio Borneo <antonio.borneo@...s.st.com>
Subject: Re: Crash on armv7-a using KASAN
On Tue, Oct 15, 2024 at 7:28 PM Ard Biesheuvel <ardb@...nel.org> wrote:
> > From a superficial look, it sounds like it should be possible to extend
> > that to also handle the KASAN shadow of the vmalloc area (which
> > __check_vmalloc_seq() currently doesn't copy), but I'm not sure of
> > exactly when we initialise the shadow for a vmalloc allocation relative
> > to updating vmalloc_seq.
>
> Indeed. It appears both vmalloc_seq() and arch_sync_kernel_mappings()
> need to take the vmalloc shadow into account specifically.
I'm trying to look into that.
> And we may
> also need the dummy read from the stack's shadow in __switch_to - I am
> pretty sure I added that for a reason.
I added that since it was simple:
>From c3c76df2a9b8132b169809dcdf93488cb43a2688 Mon Sep 17 00:00:00 2001
From: Linus Walleij <linus.walleij@...aro.org>
Date: Tue, 15 Oct 2024 22:50:38 +0200
Subject: [PATCH] ARM: entry: Do a dummy read from VMAP shadow
When switching task, in addition to a dummy read from the new
VMAP stack, also do a dummy read from the VMAP stack's
corresponding KASAN shadow memory to sync things up in
the new MM context.
Signed-off-by: Linus Walleij <linus.walleij@...aro.org>
---
arch/arm/kernel/entry-armv.S | 8 ++++++++
1 file changed, 8 insertions(+)
diff --git a/arch/arm/kernel/entry-armv.S b/arch/arm/kernel/entry-armv.S
index 1dfae1af8e31..ed2d0d89e2e9 100644
--- a/arch/arm/kernel/entry-armv.S
+++ b/arch/arm/kernel/entry-armv.S
@@ -25,6 +25,7 @@
#include <asm/tls.h>
#include <asm/system_info.h>
#include <asm/uaccess-asm.h>
+#include <asm/kasan_def.h>
#include "entry-header.S"
#include <asm/probes.h>
@@ -561,6 +562,13 @@ ENTRY(__switch_to)
@ entries covering the vmalloc region.
@
ldr r2, [ip]
+#ifdef CONFIG_KASAN
+ @ Also dummy read from the KASAN shadow memory for the new stack if we
+ @ are using KASAN
+ mov_l r2, KASAN_SHADOW_OFFSET
+ add r2, ip, lsr #KASAN_SHADOW_SCALE_SHIFT
+ ldr r2, [r2]
+#endif
#endif
@ When CONFIG_THREAD_INFO_IN_TASK=n, the update of SP itself is what
--
2.46.2
We still get crashes in do_translation_fault() so we need the more
thorough solution. Maybe this is needed too.
Yours,
Linus Walleij
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