linux-kernel - Re: [PATCH] mm/shmem.c: check the return value of mpol_to

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Date:	Tue, 03 Sep 2013 13:32:40 +0800
From:	Chen Gang <gang.chen@...anux.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
CC:	Mel Gorman <mgorman@...e.de>, kosaki.motohiro@...fujitsu.com,
	riel@...hat.com, hughd@...gle.com, xemul@...allels.com,
	rientjes@...gle.com, Wanpeng Li <liwanp@...ux.vnet.ibm.com>,
	Cyrill Gorcunov <gorcunov@...il.com>, linux-mm@...ck.org,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] mm/shmem.c: check the return value of mpol_to_str()

Hello Maintainers:

Please help check this patch, when you have time.

If it need additional test, please let me know, I should try (better to
provide some suggestions for test).


Thanks.

On 08/22/2013 09:04 AM, Chen Gang wrote:
> mpol_to_str() may fail, and not fill the buffer (e.g. -EINVAL), so need
> check about it, or buffer may not be zero based, and next seq_printf()
> will cause issue.
> 
> Also need let shmem_show_mpol() return value, since it may fail.
> 
> Signed-off-by: Chen Gang <gang.chen@...anux.com>
> Reviewed-by: Cyrill Gorcunov <gorcunov@...il.com>
> ---
>  mm/shmem.c |   16 ++++++++++------
>  1 files changed, 10 insertions(+), 6 deletions(-)
> 
> diff --git a/mm/shmem.c b/mm/shmem.c
> index f00c1c1..b4d44db 100644
> --- a/mm/shmem.c
> +++ b/mm/shmem.c
> @@ -883,16 +883,20 @@ redirty:
>  
>  #ifdef CONFIG_NUMA
>  #ifdef CONFIG_TMPFS
> -static void shmem_show_mpol(struct seq_file *seq, struct mempolicy *mpol)
> +static int shmem_show_mpol(struct seq_file *seq, struct mempolicy *mpol)
>  {
>  	char buffer[64];
> +	int ret;
>  
>  	if (!mpol || mpol->mode == MPOL_DEFAULT)
> -		return;		/* show nothing */
> +		return 0;		/* show nothing */
>  
> -	mpol_to_str(buffer, sizeof(buffer), mpol);
> +	ret = mpol_to_str(buffer, sizeof(buffer), mpol);
> +	if (ret < 0)
> +		return ret;
>  
>  	seq_printf(seq, ",mpol=%s", buffer);
> +	return 0;
>  }
>  
>  static struct mempolicy *shmem_get_sbmpol(struct shmem_sb_info *sbinfo)
> @@ -951,8 +955,9 @@ static struct page *shmem_alloc_page(gfp_t gfp,
>  }
>  #else /* !CONFIG_NUMA */
>  #ifdef CONFIG_TMPFS
> -static inline void shmem_show_mpol(struct seq_file *seq, struct mempolicy *mpol)
> +static inline int shmem_show_mpol(struct seq_file *seq, struct mempolicy *mpol)
>  {
> +	return 0;
>  }
>  #endif /* CONFIG_TMPFS */
>  
> @@ -2555,8 +2560,7 @@ static int shmem_show_options(struct seq_file *seq, struct dentry *root)
>  	if (!gid_eq(sbinfo->gid, GLOBAL_ROOT_GID))
>  		seq_printf(seq, ",gid=%u",
>  				from_kgid_munged(&init_user_ns, sbinfo->gid));
> -	shmem_show_mpol(seq, sbinfo->mpol);
> -	return 0;
> +	return shmem_show_mpol(seq, sbinfo->mpol);
>  }
>  #endif /* CONFIG_TMPFS */
>  
> 


-- 
Chen Gang
--
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