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

[Christophe Leroy]

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()

> 
> 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