Re: [PATCH v2 2/2] mm: usercopy: Warn vmalloc/module address in check_heap_object()

[Kefeng Wang]

On 2021/12/27 1:33, Christophe Leroy wrote:
> Le 25/12/2021 à 13:06, Kefeng Wang a écrit :
> > virt_addr_valid() could be insufficient to validate the virt addr
> > on some architecture, which could lead to potential BUG which has
> > been found on arm64/powerpc64.
> >
> > Let's add WARN_ON to check if the virt addr is passed virt_addr_valid()
> > but is a vmalloc/module address.
> I think that's the responsibility of the architecture and doesn't
> deserve a WARN_ON() in generic code.
>
> The generic code cannot check all what architectures do wrong.
>
> Eventually you can do some testing at startup, maybe with
> CONFIG_DEBUG_VM_PGTABLE, but I don't think we should have such
> verification in functions like check_heap_object()

Ok, we could find other better place to add a virt_to_valid() check

instead of this one.

> > Signed-off-by: Kefeng Wang <wangkefeng.wang@xxxxxxxxxx>
> > ---
> >    mm/usercopy.c | 2 ++
> >    1 file changed, 2 insertions(+)
> >
> > diff --git a/mm/usercopy.c b/mm/usercopy.c
> > index b3de3c4eefba..ce83e0b137dd 100644
> > --- a/mm/usercopy.c
> > +++ b/mm/usercopy.c
> > @@ -228,6 +228,8 @@ static inline void check_heap_object(const void *ptr, unsigned long n,
> >    	if (!virt_addr_valid(ptr))
> >    		return;
> >    
> > +	WARN_ON_ONCE(is_vmalloc_or_module_addr(ptr));
> > +
> >    	/*
> >    	 * When CONFIG_HIGHMEM=y, kmap_to_page() will give either the
> >    	 * highmem page or fallback to virt_to_page(). The following