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Date:   Wed, 13 Jul 2022 09:39:27 -0700
From:   Zach O'Keefe <zokeefe@google.com>
To:     Souptick Joarder <jrdr.linux@gmail.com>
Cc:     akpm@linux-foundation.org, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org, kernel test robot <lkp@intel.com>,
        Dan Carpenter <dan.carpenter@oracle.com>
Subject: Re: [PATCH] mm/khugepaged: Avoid possible memory leak in failure path
Message-ID: <Ys71P4AsGkzmoRQh@google.com>
References: <20220713024109.62810-1-jrdr.linux@gmail.com>
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On Jul 13 08:11, Souptick Joarder wrote:
> From: "Souptick Joarder (HPE)" <jrdr.linux@gmail.com>
> 
> smatch warnings:
> mm/khugepaged.c:2409 madvise_collapse() warn: possible memory
> leak of 'cc'
> 
> Avoiding possible memory leak.
> 
> Reported-by: kernel test robot <lkp@intel.com>
> Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
> Signed-off-by: Souptick Joarder (HPE) <jrdr.linux@gmail.com>
> ---
>  mm/khugepaged.c | 12 ++++++------
>  1 file changed, 6 insertions(+), 6 deletions(-)
> 
> diff --git a/mm/khugepaged.c b/mm/khugepaged.c
> index 0207fc0a5b2a..8da9e7467543 100644
> --- a/mm/khugepaged.c
> +++ b/mm/khugepaged.c
> @@ -2397,12 +2397,6 @@ int madvise_collapse(struct vm_area_struct *vma, struct vm_area_struct **prev,
>  	BUG_ON(vma->vm_start > start);
>  	BUG_ON(vma->vm_end < end);
>  
> -	cc = kmalloc(sizeof(*cc), GFP_KERNEL);
> -	if (!cc)
> -		return -ENOMEM;
> -	cc->is_khugepaged = false;
> -	cc->last_target_node = NUMA_NO_NODE;
> -
>  	*prev = vma;
>  
>  	/* TODO: Support file/shmem */
> @@ -2415,6 +2409,12 @@ int madvise_collapse(struct vm_area_struct *vma, struct vm_area_struct **prev,
>  	if (!hugepage_vma_check(vma, vma->vm_flags, false, false, false))
>  		return -EINVAL;
>  
> +	cc = kmalloc(sizeof(*cc), GFP_KERNEL);
> +	if (!cc)
> +		return -ENOMEM;
> +	cc->is_khugepaged = false;
> +	cc->last_target_node = NUMA_NO_NODE;
> +
>  	mmgrab(mm);
>  	lru_add_drain_all();
>  
> -- 
> 2.25.1
> 
> 

Thanks for the fix!

I've also sent out another patch on top which addresses the actual missing
kfree()