linux-kernel - Re: [PATCH] mm: vmalloc: fix uninitialized value issue

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Message-Id: <20251014190916.e9285e8ac6a8301cdacd9fe8@linux-foundation.org>
Date: Tue, 14 Oct 2025 19:09:16 -0700
From: Andrew Morton <akpm@...ux-foundation.org>
To: Yadong Qi <yadong.qi@...ux.alibaba.com>
Cc: urezki@...il.com, linux-mm@...ck.org, linux-kernel@...r.kernel.org,
 ying.huang@...ux.alibaba.com, dan.carpenter@...aro.org, kernel test robot
 <lkp@...el.com>, Huang Ying <ying.huang@...ux.alibaba.com>, Dev Jain
 <dev.jain@....com>, Uladzislau Rezki (Sony) <urezki@...il.com>
Subject: Re: [PATCH] mm: vmalloc: fix uninitialized value issue

On Tue, 14 Oct 2025 18:23:37 +0800 Yadong Qi <yadong.qi@...ux.alibaba.com> wrote:

> Issues reported by LKP:
>   mm/vmalloc.c:191 vmap_pmd_range() error: uninitialized symbol 'err'.
>   mm/vmalloc.c:243 vmap_pud_range() error: uninitialized symbol 'err'.
>   mm/vmalloc.c:295 vmap_p4d_range() error: uninitialized symbol 'err'.
> 
> Fix by initailizing err with 0.

This fixes warnings which were introduced by mm.git's recent "mm:
vmalloc: WARN_ON if mapping size is not PAGE_SIZE aligned".  Please do
point out such details.

> --- a/mm/vmalloc.c
> +++ b/mm/vmalloc.c
> @@ -170,7 +170,7 @@ static int vmap_pmd_range(pud_t *pud, unsigned long addr, unsigned long end,
>  {
>  	pmd_t *pmd;
>  	unsigned long next;
> -	int err;
> +	int err = 0;
>  
>  	pmd = pmd_alloc_track(&init_mm, pud, addr, mask);
>  	if (!pmd)

So we get the below:

: static int vmap_pmd_range(pud_t *pud, unsigned long addr, unsigned long end,
: 			phys_addr_t phys_addr, pgprot_t prot,
: 			unsigned int max_page_shift, pgtbl_mod_mask *mask)
: {
: 	pmd_t *pmd;
: 	unsigned long next;
: 	int err = 0;
: 
: 	pmd = pmd_alloc_track(&init_mm, pud, addr, mask);
: 	if (!pmd)
: 		return -ENOMEM;
: 	do {
: 		next = pmd_addr_end(addr, end);
: 
: 		if (vmap_try_huge_pmd(pmd, addr, next, phys_addr, prot,
: 					max_page_shift)) {
: 			*mask |= PGTBL_PMD_MODIFIED;
: 			continue;
: 		}
: 
: 		err = vmap_pte_range(pmd, addr, next, phys_addr, prot, max_page_shift, mask);
: 		if (err)
: 			break;
: 	} while (pmd++, phys_addr += (next - addr), addr = next, addr != end);
: 	return err;
: }

If every single pmd fails vmap_try_huge_pmd() then this function
returns zero, indicating success.  Is this behavior correct and
desirable?