linux-kernel.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
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 v2 2/3] fork: support VMAP_STACK with KASAN_VMALLOC
Date: Tue, 30 Jul 2019 00:21:07 +1000	[thread overview]
Message-ID: <20190729142108.23343-3-dja@axtens.net> (raw)
In-Reply-To: <20190729142108.23343-1-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


  parent reply	other threads:[~2019-07-29 14:21 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-07-29 14:21 [PATCH v2 0/3] kasan: support backing vmalloc space with real shadow memory Daniel Axtens
2019-07-29 14:21 ` [PATCH v2 1/3] " Daniel Axtens
2019-07-29 15:44   ` Mark Rutland
2019-07-30  8:38     ` Daniel Axtens
2019-07-31  6:34       ` Daniel Axtens
2019-07-29 14:21 ` Daniel Axtens [this message]
2019-07-29 14:21 ` [PATCH v2 3/3] x86/kasan: support KASAN_VMALLOC Daniel Axtens

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20190729142108.23343-3-dja@axtens.net \
    --to=dja@axtens.net \
    --cc=aryabinin@virtuozzo.com \
    --cc=dvyukov@google.com \
    --cc=glider@google.com \
    --cc=kasan-dev@googlegroups.com \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-mm@kvack.org \
    --cc=luto@kernel.org \
    --cc=mark.rutland@arm.com \
    --cc=x86@kernel.org \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).