Re: [PATCH v2 1/3] mm/vmalloc: fix vmalloc_dump_obj address alignment for last-page lookups

[Uladzislau Rezki <urezki@gmail.com>]

On Mon, Sep 21, 2026 at 09:17:21PM +0800, Ye Liu wrote:
> From: Ye Liu <liuye@kylinos.cn>
> 
> vmalloc_dump_obj() uses PAGE_ALIGN() to normalize the input address
> before looking it up in the per-node busy tree.  PAGE_ALIGN() rounds
> up, which can push an address in the last page of a vmalloc allocation
> to va_end -- outside the [va_start, va_end) range that
> __find_vmap_area() searches.  This causes the lookup to miss the VA
> and return false, degrading diagnostic output in OOM dumps and KASAN
> reports to the less informative "vmalloc memory" fallback.
> 
> The upward alignment can also change the addr_to_node() mapping when
> the page boundary crosses a vmap zone boundary, causing the search to
> hit the wrong node entirely.
> 
> Use PAGE_ALIGN_DOWN() instead, which rounds down to the page
> containing the address.  This keeps the address within the VA range
> and preserves the correct node mapping.
> 
> Signed-off-by: Ye Liu <liuye@kylinos.cn>
> ---
>  mm/vmalloc.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/mm/vmalloc.c b/mm/vmalloc.c
> index 859e6d2d57a3..df42d8a6f058 100644
> --- a/mm/vmalloc.c
> +++ b/mm/vmalloc.c
> @@ -5277,7 +5277,7 @@ bool vmalloc_dump_obj(void *object)
>  	unsigned long addr;
>  	unsigned long nr_pages;
>  
> -	addr = PAGE_ALIGN((unsigned long) object);
> +	addr = PAGE_ALIGN_DOWN((unsigned long) object);
>  	vn = addr_to_node(addr);
>  
>  	if (!spin_trylock(&vn->busy.lock))
> 
> -- 
> 2.25.1
> 
LGTM:

Reviewed-by: Uladzislau Rezki (Sony) <urezki@gmail.com>

--
Uladzislau Rezki