linux-kernel - Re: [PATCH] nvdimm-btt: fix a potential memleak in btt_freelist

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Message-ID: <23a91617-4562-4399-a8c6-df2f3f28c7a9@intel.com>
Date:   Thu, 7 Dec 2023 08:43:42 -0700
From:   Dave Jiang <dave.jiang@...el.com>
To:     Dinghao Liu <dinghao.liu@....edu.cn>
CC:     Vishal Verma <vishal.l.verma@...el.com>,
        Dan Williams <dan.j.williams@...el.com>,
        Ira Weiny <ira.weiny@...el.com>, <nvdimm@...ts.linux.dev>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] nvdimm-btt: fix a potential memleak in btt_freelist_init



On 12/6/23 20:43, Dinghao Liu wrote:
> When an error happens in btt_freelist_init(), its caller
> discover_arenas() will directly free arena, which makes
> arena->freelist allocated in btt_freelist_init() a leaked
> memory. Fix this by freeing arena->freelist in all error
> handling paths of btt_freelist_init().
> 
> Fixes: 5212e11fde4d ("nd_btt: atomic sector updates")
> Signed-off-by: Dinghao Liu <dinghao.liu@....edu.cn>

How about use the new scope based resource management and we can avoid the goto mess altogether?
https://lwn.net/Articles/934679/


> ---
>  drivers/nvdimm/btt.c | 15 +++++++++++----
>  1 file changed, 11 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/nvdimm/btt.c b/drivers/nvdimm/btt.c
> index d5593b0dc700..d8c4ba8bfdda 100644
> --- a/drivers/nvdimm/btt.c
> +++ b/drivers/nvdimm/btt.c
> @@ -544,8 +544,10 @@ static int btt_freelist_init(struct arena_info *arena)
>  
>  	for (i = 0; i < arena->nfree; i++) {
>  		new = btt_log_read(arena, i, &log_new, LOG_NEW_ENT);
> -		if (new < 0)
> -			return new;
> +		if (new < 0) {
> +			ret = new;
> +			goto out_free;
> +		}
>  
>  		/* old and new map entries with any flags stripped out */
>  		log_oldmap = ent_lba(le32_to_cpu(log_new.old_map));
> @@ -577,7 +579,7 @@ static int btt_freelist_init(struct arena_info *arena)
>  		ret = btt_map_read(arena, le32_to_cpu(log_new.lba), &map_entry,
>  				NULL, NULL, 0);
>  		if (ret)
> -			return ret;
> +			goto out_free;
>  
>  		/*
>  		 * The map_entry from btt_read_map is stripped of any flag bits,
> @@ -594,11 +596,16 @@ static int btt_freelist_init(struct arena_info *arena)
>  			ret = btt_map_write(arena, le32_to_cpu(log_new.lba),
>  					le32_to_cpu(log_new.new_map), 0, 0, 0);
>  			if (ret)
> -				return ret;
> +				goto out_free;
>  		}
>  	}
>  
>  	return 0;
> +
> +out_free:
> +	kfree(arena->freelist);
> +	arena->freelist = NULL;
> +	return ret;
>  }
>  
>  static bool ent_is_padding(struct log_entry *ent)