Commit eafb149e authored by Daniel Axtens's avatar Daniel Axtens Committed by Linus Torvalds
Browse files

fork: support VMAP_STACK with KASAN_VMALLOC 

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

Link: http://lkml.kernel.org/r/20191031093909.9228-4-dja@axtens.net


Signed-off-by: default avatarDaniel Axtens <dja@axtens.net>
Reviewed-by: default avatarDmitry Vyukov <dvyukov@google.com>
Reviewed-by: default avatarAndrey Ryabinin <aryabinin@virtuozzo.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Christophe Leroy <christophe.leroy@c-s.fr>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Vasily Gorbik <gor@linux.ibm.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 06513916

arch/Kconfig

+5 −4
Original line number Original line Diff line number Diff line
@@ -843,16 +843,17 @@ config HAVE_ARCH_VMAP_STACK 
config VMAP_STACK

config VMAP_STACK

	default y

	default y

	bool "Use a virtually-mapped stack"

	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---

	---help---

	  Enable this if you want the use virtually-mapped kernel stacks

	  Enable this if you want the use virtually-mapped kernel stacks

	  with guard pages.  This causes kernel stack overflows to be

	  with guard pages.  This causes kernel stack overflows to be

	  caught immediately rather than causing difficult-to-diagnose

	  caught immediately rather than causing difficult-to-diagnose

	  corruption.

	  corruption.





	  This is presently incompatible with KASAN because KASAN expects

	  To use this with KASAN, the architecture must support backing

	  the stack to map directly to the KASAN shadow map using a formula

	  virtual mappings with real shadow memory, and KASAN_VMALLOC must

	  that is incorrect if the stack is in vmalloc space.

	  be enabled.





config ARCH_OPTIONAL_KERNEL_RWX

config ARCH_OPTIONAL_KERNEL_RWX

	def_bool n

	def_bool n

kernel/fork.c

+4 −0
Original line number Original line Diff line number Diff line
@@ -93,6 +93,7 @@ 
#include <linux/livepatch.h>

#include <linux/livepatch.h>

#include <linux/thread_info.h>

#include <linux/thread_info.h>

#include <linux/stackleak.h>

#include <linux/stackleak.h>

#include <linux/kasan.h>





#include <asm/pgtable.h>

#include <asm/pgtable.h>

#include <asm/pgalloc.h>

#include <asm/pgalloc.h>
@@ -223,6 +224,9 @@ static unsigned long *alloc_thread_stack_node(struct task_struct *tsk, int node) 
		if (!s)

		if (!s)

			continue;

			continue;





		/* Clear the KASAN shadow of the stack. */

		kasan_unpoison_shadow(s->addr, THREAD_SIZE);



		/* Clear stale pointers from reused stack. */

		/* Clear stale pointers from reused stack. */

		memset(s->addr, 0, THREAD_SIZE);

		memset(s->addr, 0, THREAD_SIZE);