From: Daniel Axtens <dja@axtens.net>
To: kasan-dev@googlegroups.com, linux-mm@kvack.org, x86@kernel.org,
aryabinin@virtuozzo.com, glider@google.com, luto@kernel.org,
linux-kernel@vger.kernel.org, mark.rutland@arm.com,
dvyukov@google.com
Cc: Daniel Axtens <dja@axtens.net>
Subject: [PATCH v3 2/3] fork: support VMAP_STACK with KASAN_VMALLOC
Date: Wed, 31 Jul 2019 17:15:49 +1000 [thread overview]
Message-ID: <20190731071550.31814-3-dja@axtens.net> (raw)
In-Reply-To: <20190731071550.31814-1-dja@axtens.net>
Supporting VMAP_STACK with KASAN_VMALLOC is straightforward:
- clear the shadow region of vmapped stacks when swapping them in
- tweak Kconfig to allow VMAP_STACK to be turned on with KASAN
Reviewed-by: Dmitry Vyukov <dvyukov@google.com>
Signed-off-by: Daniel Axtens <dja@axtens.net>
---
arch/Kconfig | 9 +++++----
kernel/fork.c | 4 ++++
2 files changed, 9 insertions(+), 4 deletions(-)
diff --git a/arch/Kconfig b/arch/Kconfig
index a7b57dd42c26..e791196005e1 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -825,16 +825,17 @@ config HAVE_ARCH_VMAP_STACK
config VMAP_STACK
default y
bool "Use a virtually-mapped stack"
- depends on HAVE_ARCH_VMAP_STACK && !KASAN
+ depends on HAVE_ARCH_VMAP_STACK
+ depends on !KASAN || KASAN_VMALLOC
---help---
Enable this if you want the use virtually-mapped kernel stacks
with guard pages. This causes kernel stack overflows to be
caught immediately rather than causing difficult-to-diagnose
corruption.
- This is presently incompatible with KASAN because KASAN expects
- the stack to map directly to the KASAN shadow map using a formula
- that is incorrect if the stack is in vmalloc space.
+ To use this with KASAN, the architecture must support backing
+ virtual mappings with real shadow memory, and KASAN_VMALLOC must
+ be enabled.
config ARCH_OPTIONAL_KERNEL_RWX
def_bool n
diff --git a/kernel/fork.c b/kernel/fork.c
index d8ae0f1b4148..ce3150fe8ff2 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -94,6 +94,7 @@
#include <linux/livepatch.h>
#include <linux/thread_info.h>
#include <linux/stackleak.h>
+#include <linux/kasan.h>
#include <asm/pgtable.h>
#include <asm/pgalloc.h>
@@ -215,6 +216,9 @@ static unsigned long *alloc_thread_stack_node(struct task_struct *tsk, int node)
if (!s)
continue;
+ /* Clear the KASAN shadow of the stack. */
+ kasan_unpoison_shadow(s->addr, THREAD_SIZE);
+
/* Clear stale pointers from reused stack. */
memset(s->addr, 0, THREAD_SIZE);
--
2.20.1
next prev parent reply other threads:[~2019-07-31 7:16 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-07-31 7:15 [PATCH v3 0/3] kasan: support backing vmalloc space with real shadow memory Daniel Axtens
2019-07-31 7:15 ` [PATCH v3 1/3] " Daniel Axtens
2019-08-08 13:50 ` Mark Rutland
2019-08-08 17:43 ` Mark Rutland
2019-08-09 9:54 ` Mark Rutland
2019-08-12 2:53 ` Daniel Axtens
2019-08-09 12:37 ` Mark Rutland
2019-08-09 11:54 ` Vasily Gorbik
2019-07-31 7:15 ` Daniel Axtens [this message]
2019-07-31 7:15 ` [PATCH v3 3/3] x86/kasan: support KASAN_VMALLOC Daniel Axtens
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