linux-kernel - Re: [PATCH v2 5/5] mm/vmalloc.c: avoid endless loop under v[un]mapping improper ranges

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Message-ID: <57E4C439.5080701@zoho.com>
Date:   Fri, 23 Sep 2016 13:57:13 +0800
From:   zijun_hu <zijun_hu@...o.com>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org, zijun_hu@....com,
        tj@...nel.org, mingo@...nel.org, rientjes@...gle.com,
        iamjoonsoo.kim@....com, mgorman@...hsingularity.net
Subject: Re: [PATCH v2 5/5] mm/vmalloc.c: avoid endless loop under
 v[un]mapping improper ranges

On 09/21/2016 12:34 PM, zijun_hu wrote:
> From: zijun_hu <zijun_hu@....com>
> 
> fix the following bug:
>  - endless loop maybe happen when v[un]mapping improper ranges
>    whose either boundary is not aligned to page
> 
> Signed-off-by: zijun_hu <zijun_hu@....com>
> ---
>  mm/vmalloc.c | 9 +++++++--
>  1 file changed, 7 insertions(+), 2 deletions(-)
> 
> diff --git a/mm/vmalloc.c b/mm/vmalloc.c
> index 5eeecc3..16fe957 100644
> --- a/mm/vmalloc.c
> +++ b/mm/vmalloc.c
> @@ -67,7 +67,7 @@ static void vunmap_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end)
>  	do {
>  		pte_t ptent = ptep_get_and_clear(&init_mm, addr, pte);
>  		WARN_ON(!pte_none(ptent) && !pte_present(ptent));
> -	} while (pte++, addr += PAGE_SIZE, addr != end);
> +	} while (pte++, addr += PAGE_SIZE, addr < end && addr >= PAGE_SIZE);
>  }
>  
>  static void vunmap_pmd_range(pud_t *pud, unsigned long addr, unsigned long end)
> @@ -108,6 +108,9 @@ static void vunmap_page_range(unsigned long addr, unsigned long end)
>  	unsigned long next;
>  
>  	BUG_ON(addr >= end);
> +	WARN_ON(!PAGE_ALIGNED(addr) || !PAGE_ALIGNED(end));
> +
> +	addr = round_down(addr, PAGE_SIZE);
>  	pgd = pgd_offset_k(addr);
>  	do {
>  		next = pgd_addr_end(addr, end);
> @@ -139,7 +142,7 @@ static int vmap_pte_range(pmd_t *pmd, unsigned long addr,
>  			return -ENOMEM;
>  		set_pte_at(&init_mm, addr, pte, mk_pte(page, prot));
>  		(*nr)++;
> -	} while (pte++, addr += PAGE_SIZE, addr != end);
> +	} while (pte++, addr += PAGE_SIZE, addr < end);
>  	return 0;
>  }
>  
> @@ -193,6 +196,8 @@ static int vmap_page_range_noflush(unsigned long start, unsigned long end,
>  	int nr = 0;
>  
>  	BUG_ON(addr >= end);
> +	BUG_ON(!PAGE_ALIGNED(addr) || !PAGE_ALIGNED(end));
> +
>  	pgd = pgd_offset_k(addr);
>  	do {
>  		next = pgd_addr_end(addr, end);
> 
From: zijun_hu <zijun_hu@....com>

s/WARN_ON()/WARN_ON_ONCE()/ to reduce warning messages

Signed-off-by: zijun_hu <zijun_hu@....com>
---
 mm/vmalloc.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index 16fe957..e34031e 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -108,7 +108,7 @@ static void vunmap_page_range(unsigned long addr, unsigned long end)
 	unsigned long next;
 
 	BUG_ON(addr >= end);
-	WARN_ON(!PAGE_ALIGNED(addr) || !PAGE_ALIGNED(end));
+	WARN_ON_ONCE(!PAGE_ALIGNED(addr) || !PAGE_ALIGNED(end));
 
 	addr = round_down(addr, PAGE_SIZE);
 	pgd = pgd_offset_k(addr);
-- 
1.9.1