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SubjectRe: [PATCH mm] fix for "kasan, fork: reset pointer tags of vmapped stacks"
On Tue, 15 Feb 2022 at 17:52, <andrey.konovalov@linux.dev> wrote:
>
> From: Andrey Konovalov <andreyknvl@google.com>
>
> That patch didn't update the case when a stack is retrived from
> cached_stacks in alloc_thread_stack_node(). As cached_stacks stores
> vm_structs and not stack pointers themselves, the pointer tag needs
> to be reset there as well.
>
> Signed-off-by: Andrey Konovalov <andreyknvl@google.com>

Reviewed-by: Marco Elver <elver@google.com>

Did the test catch this? If not, can this be tested?

> ---
> kernel/fork.c | 10 ++++++----
> 1 file changed, 6 insertions(+), 4 deletions(-)
>
> diff --git a/kernel/fork.c b/kernel/fork.c
> index 57d624f05182..5e3ad2e7a756 100644
> --- a/kernel/fork.c
> +++ b/kernel/fork.c
> @@ -226,15 +226,17 @@ static unsigned long *alloc_thread_stack_node(struct task_struct *tsk, int node)
> if (!s)
> continue;
>
> - /* Mark stack accessible for KASAN. */
> + /* Reset stack metadata. */
> kasan_unpoison_range(s->addr, THREAD_SIZE);
>
> + stack = kasan_reset_tag(s->addr);
> +
> /* Clear stale pointers from reused stack. */
> - memset(s->addr, 0, THREAD_SIZE);
> + memset(stack, 0, THREAD_SIZE);
>
> tsk->stack_vm_area = s;
> - tsk->stack = s->addr;
> - return s->addr;
> + tsk->stack = stack;
> + return stack;
> }
>
> /*
> --
> 2.25.1
>

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