linux-kernel - Re: [PATCH v2] mm: vmalloc: WARN_ON if mapping size is not PAGE

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Message-ID: <87zfa0tw9o.fsf@DESKTOP-5N7EMDA>
Date: Thu, 09 Oct 2025 14:38:27 +0800
From: "Huang, Ying" <ying.huang@...ux.alibaba.com>
To: Yadong Qi <yadong.qi@...ux.alibaba.com>
Cc: akpm@...ux-foundation.org,  urezki@...il.com,  linux-mm@...ck.org,
  linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] mm: vmalloc: WARN_ON if mapping size is not
 PAGE_SIZE aligned

Yadong Qi <yadong.qi@...ux.alibaba.com> writes:

> In mm/vmalloc.c, the function vmap_pte_range() assumes that the
> mapping size is aligned to PAGE_SIZE. If this assumption is
> violated, the loop will become infinite because the termination
> condition (`addr != end`) will never be met. This can lead to
> overwriting other VA ranges and/or random pages physically follow
> the page table.
>
> It's the caller's responsibility to ensure that the mapping size
> is aligned to PAGE_SIZE. However, the memory corruption is hard
> to root cause. To identify the programming error in the caller
> easier, check whether the mapping size is PAGE_SIZE aligned with
> WARN_ON().
>
> Signed-off-by: Yadong Qi <yadong.qi@...ux.alibaba.com>
> Reviewed-by: Huang Ying <ying.huang@...ux.alibaba.com>
> ---
> v1 -> v2:
>   * Use WARN_ON instead of BUG_ON
> ---
>  mm/vmalloc.c | 3 +++
>  1 file changed, 3 insertions(+)
>
> diff --git a/mm/vmalloc.c b/mm/vmalloc.c
> index 5edd536ba9d2..2cad593e4677 100644
> --- a/mm/vmalloc.c
> +++ b/mm/vmalloc.c
> @@ -100,6 +100,9 @@ static int vmap_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end,
>  	struct page *page;
>  	unsigned long size = PAGE_SIZE;
>  
> +	if (WARN_ON(!PAGE_ALIGNED(end - addr)))
> +		return -ENOMEM;
> +

EINVAL?

>  	pfn = phys_addr >> PAGE_SHIFT;
>  	pte = pte_alloc_kernel_track(pmd, addr, mask);
>  	if (!pte)

---
Best Regards,
Huang, Ying