Re: [PATCH v10 3/5] fork: support VMAP_STACK with KASAN_VMALLOC
From: Andrey Ryabinin <hidden>
Date: 2019-10-29 17:07:37
Also in:
linux-mm, lkml
On 10/29/19 7:20 AM, Daniel Axtens wrote:
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 <redacted> ---
Reviewed-by: Andrey Ryabinin <redacted>
quoted hunk ↗ jump to hunk
diff --git a/kernel/fork.c b/kernel/fork.c index 954e875e72b1..a6e5249ad74b 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); +
Just sharing the thought. We could possibly add poisoning in free_thread_stack() to catch possible usage of freed cached stack. But it might be a bad idea because cached stacks supposed to be reused very quickly. So it might just add overhead without much gain.
/* Clear stale pointers from reused stack. */ memset(s->addr, 0, THREAD_SIZE);