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fork: support VMAP_STACK with KASAN_VMALLOC

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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: Daniel Axtens <dja@axtens.net>
Reviewed-by: Dmitry Vyukov <dvyukov@google.com>
Reviewed-by: Andrey 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: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Daniel Axtens 2019-11-30 17:54:57 -08:00 committed by Linus Torvalds
parent 0651391693
commit eafb149ed7
2 changed files with 9 additions and 4 deletions
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9
arch/Kconfig
View File

@ -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

4
kernel/fork.c
View File

@ -93,6 +93,7 @@
#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>
@ -223,6 +224,9 @@ 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);