Re: [PATCH v3] mm: vmalloc: WARN_ON if mapping size is not PAGE_SIZE aligned

[Uladzislau Rezki <urezki@gmail.com>]

On Thu, Oct 09, 2025 at 05:37:06PM +0800, Yadong Qi wrote:
> 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@linux.alibaba.com>
> Reviewed-by: Huang Ying <ying.huang@linux.alibaba.com>
> ---
> v2 -> v3:
>   * change error code from ENOMEM to EINVAL
>   * modify callers of vmap_pte_range to handle return code
> v1 -> v2:
>   * Use WARN_ON instead of BUG_ON
> ---
>  mm/vmalloc.c | 29 ++++++++++++++++++-----------
>  1 file changed, 18 insertions(+), 11 deletions(-)
> 
> diff --git a/mm/vmalloc.c b/mm/vmalloc.c
> index 5edd536ba9d2..1fa52f203795 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)))
>
And it might be worth to use WARN_ON_ONCE() otherwise there is a risk
that a kernel buffer would contain only such warnings.

--
Uladzislau Rezki