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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, christophe.leroy@c-s.fr
Cc: linuxppc-dev@lists.ozlabs.org, gor@linux.ibm.com,
	Daniel Axtens <dja@axtens.net>
Subject: [PATCH v11 3/4] fork: support VMAP_STACK with KASAN_VMALLOC
Date: Thu, 31 Oct 2019 20:39:08 +1100	[thread overview]
Message-ID: <20191031093909.9228-4-dja@axtens.net> (raw)
In-Reply-To: <20191031093909.9228-1-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>
Reviewed-by: Andrey Ryabinin <aryabinin@virtuozzo.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 5f8a5d84dbbe..2d914990402f 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -843,16 +843,17 @@ 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 4b2a82eda8e5..0eef4243019c 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>
@@ -224,6 +225,9 @@ 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


  parent reply	other threads:[~2019-10-31  9:39 UTC|newest]

Thread overview: 47+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-10-31  9:39 [PATCH v11 0/4] kasan: support backing vmalloc space with real shadow memory Daniel Axtens
2019-10-31  9:39 ` [PATCH v11 1/4] " Daniel Axtens
2019-11-15 16:36   ` Qian Cai
2019-11-15 16:36     ` Qian Cai
2019-11-18  3:29     ` Daniel Axtens
2019-11-19  9:54       ` Andrey Ryabinin
2019-11-29 10:43         ` Dmitry Vyukov
2019-11-29 10:43           ` Dmitry Vyukov
2019-11-29 10:43           ` Dmitry Vyukov
2019-11-29 10:58           ` Dmitry Vyukov
2019-11-29 10:58             ` Dmitry Vyukov
2019-11-29 10:58             ` Dmitry Vyukov
2019-11-29 11:02             ` Dmitry Vyukov
2019-11-29 11:02               ` Dmitry Vyukov
2019-11-29 11:02               ` Dmitry Vyukov
2019-11-29 11:38               ` Andrey Ryabinin
2019-11-29 11:38                 ` Andrey Ryabinin
2019-11-29 11:47                 ` Dmitry Vyukov
2019-11-29 11:47                   ` Dmitry Vyukov
2019-11-29 11:47                   ` Dmitry Vyukov
2019-11-29 11:53                   ` Andrey Ryabinin
2019-11-29 11:53                     ` Andrey Ryabinin
2019-11-29 12:29                     ` Daniel Axtens
2019-11-29 12:29                       ` Daniel Axtens
2019-11-29 12:45                       ` Dmitry Vyukov
2019-11-29 12:45                         ` Dmitry Vyukov
2019-11-29 12:45                         ` Dmitry Vyukov
2019-11-29 15:13                         ` Dmitry Vyukov
2019-11-29 15:13                           ` Dmitry Vyukov
2019-11-29 15:13                           ` Dmitry Vyukov
2019-11-29 15:15                       ` XFS check crash (WAS Re: [PATCH v11 1/4] kasan: support backing vmalloc space with real shadow memory) Qian Cai
2019-11-29 15:15                         ` Qian Cai
2019-11-29 15:50                         ` Daniel Axtens
2019-11-29 15:50                           ` Daniel Axtens
2019-11-29 12:09             ` [PATCH v11 1/4] kasan: support backing vmalloc space with real shadow memory Daniel Axtens
2019-11-29 12:09               ` Daniel Axtens
2019-11-29 12:15               ` Dmitry Vyukov
2019-11-29 12:15                 ` Dmitry Vyukov
2019-11-29 12:15                 ` Dmitry Vyukov
2019-11-20  5:27   ` [PATCH] update to "kasan: support backing vmalloc space with real shadow memory" Daniel Axtens
2019-11-20  5:27     ` Daniel Axtens
2019-10-31  9:39 ` [PATCH v11 2/4] kasan: add test for vmalloc Daniel Axtens
2019-10-31  9:39 ` Daniel Axtens [this message]
2019-10-31  9:39 ` [PATCH v11 4/4] x86/kasan: support KASAN_VMALLOC Daniel Axtens
2019-11-08 22:36 ` [PATCH v11 0/4] kasan: support backing vmalloc space with real shadow memory Andrey Ryabinin
2019-11-08 22:36   ` Andrey Ryabinin
2019-12-02  8:07 ` Christophe Leroy

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