linux-kernel - Re: [PATCH 2/2] ARM: dma-mapping: fix leak in consistent

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Date:	Sat, 18 Feb 2012 15:58:33 +0000
From:	Tixy <tixy@...t.co.uk>
To:	Ajeet Yadav <ajeet.yadav.77@...il.com>
Cc:	Russell King <linux@....linux.org.uk>,
	Nicolas Pitre <nicolas.pitre@...aro.org>,
	Catalin Marinas <catalin.marinas@....com>,
	Sumit Bhattacharya <sumitb@...dia.com>,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] ARM: dma-mapping: fix leak in consistent_init

On Fri, 2012-02-17 at 18:39 +0530, Ajeet Yadav wrote:
> Although the error in this case is unlikely, but logically
> if error occurs then we leak memory.
> 
> Signed-off-by: Ajeet Yadav <ajeet.yadav.77@...il.com>

If you want to fix all the memory leaks then the page tables allocated
by pte_alloc_kernel() need freeing as well, (and the pud and pmd
tables?).

However, if we run out of memory this early in boot, then the system is
unusable anyway and it doesn't seem worth adding the extra code
complexity to avoid any of these memory leaks.

-- 
Tixy

> ---
>  arch/arm/mm/dma-mapping.c |   24 ++++++++++++------------
>  1 files changed, 12 insertions(+), 12 deletions(-)
> 
> diff --git a/arch/arm/mm/dma-mapping.c b/arch/arm/mm/dma-mapping.c
> index 04bfa76..b8cf062 100644
> --- a/arch/arm/mm/dma-mapping.c
> +++ b/arch/arm/mm/dma-mapping.c
> @@ -161,7 +161,6 @@ static struct arm_vmregion_head consistent_head = {
>   */
>  static int __init consistent_init(void)
>  {
> -	int ret = 0;
>  	pgd_t *pgd;
>  	pud_t *pud;
>  	pmd_t *pmd;
> @@ -171,7 +170,7 @@ static int __init consistent_init(void)
>  	unsigned long num_ptes = (CONSISTENT_END - base) >> PMD_SHIFT;
>  
>  	consistent_pte = kmalloc(num_ptes * sizeof(pte_t *), GFP_KERNEL);
> -	if (!consistent_pte) {
> +	if (unlikely(!consistent_pte)) {
>  		pr_err("%s: no memory\n", __func__);
>  		return -ENOMEM;
>  	}
> @@ -183,32 +182,33 @@ static int __init consistent_init(void)
>  		pgd = pgd_offset(&init_mm, base);
>  
>  		pud = pud_alloc(&init_mm, pgd, base);
> -		if (!pud) {
> +		if (unlikely(!pud)) {
>  			printk(KERN_ERR "%s: no pud tables\n", __func__);
> -			ret = -ENOMEM;
> -			break;
> +			goto err;
>  		}
>  
>  		pmd = pmd_alloc(&init_mm, pud, base);
> -		if (!pmd) {
> +		if (unlikely(!pmd)) {
>  			printk(KERN_ERR "%s: no pmd tables\n", __func__);
> -			ret = -ENOMEM;
> -			break;
> +			goto err;
>  		}
>  		WARN_ON(!pmd_none(*pmd));
>  
>  		pte = pte_alloc_kernel(pmd, base);
> -		if (!pte) {
> +		if (unlikely(!pte)) {
>  			printk(KERN_ERR "%s: no pte tables\n", __func__);
> -			ret = -ENOMEM;
> -			break;
> +			goto err;
>  		}
>  
>  		consistent_pte[i++] = pte;
>  		base += PMD_SIZE;
>  	} while (base < CONSISTENT_END);
>  
> -	return ret;
> +	return 0;
> +err:
> +	kfree(consistent_pte);
> +	consistent_pte = NULL;
> +	return -ENOMEM;
>  }
>  
>  core_initcall(consistent_init);



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