| From | Alexander Potapenko <> | Date | Tue, 21 Dec 2021 16:11:11 +0100 | Subject | Re: [PATCH mm v4 22/39] kasan, fork: reset pointer tags of vmapped stacks |
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On Mon, Dec 20, 2021 at 11:01 PM <andrey.konovalov@linux.dev> wrote: > > From: Andrey Konovalov <andreyknvl@google.com> > > Once tag-based KASAN modes start tagging vmalloc() allocations, > kernel stacks start getting tagged if CONFIG_VMAP_STACK is enabled. > > Reset the tag of kernel stack pointers after allocation in > alloc_thread_stack_node(). > > For SW_TAGS KASAN, when CONFIG_KASAN_STACK is enabled, the > instrumentation can't handle the SP register being tagged. > > For HW_TAGS KASAN, there's no instrumentation-related issues. However, > the impact of having a tagged SP register needs to be properly evaluated, > so keep it non-tagged for now. > > Note, that the memory for the stack allocation still gets tagged to > catch vmalloc-into-stack out-of-bounds accesses. > > Signed-off-by: Andrey Konovalov <andreyknvl@google.com> Reviewed-by: Alexander Potapenko <glider@google.com> > > --- > > Changes v2->v3: > - Update patch description. > --- > kernel/fork.c | 1 + > 1 file changed, 1 insertion(+) > > diff --git a/kernel/fork.c b/kernel/fork.c > index 403b9dbbfb62..4125373dba4e 100644 > --- a/kernel/fork.c > +++ b/kernel/fork.c > @@ -254,6 +254,7 @@ static unsigned long *alloc_thread_stack_node(struct task_struct *tsk, int node) > * so cache the vm_struct. > */ > if (stack) { > + stack = kasan_reset_tag(stack); > tsk->stack_vm_area = find_vm_area(stack); > tsk->stack = stack; > } > -- > 2.25.1 >
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