linux-kernel - Re: [PATCH v2] f2fs: cleanup in f2fs_create_flush_cmd

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Message-ID: <5cc0d3cd-8b32-0a05-f662-e2ec4f784900@kernel.org>
Date:   Tue, 25 Oct 2022 15:58:37 +0800
From:   Chao Yu <chao@...nel.org>
To:     Yangtao Li <frank.li@...o.com>, jaegeuk@...nel.org
Cc:     linux-f2fs-devel@...ts.sourceforge.net,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] f2fs: cleanup in f2fs_create_flush_cmd_control()

On 2022/10/25 15:56, Yangtao Li wrote:
> Remove the local 'err' variable for readable,
> no functional changes.
> 
> Signed-off-by: Yangtao Li <frank.li@...o.com>
> ---
>   fs/f2fs/segment.c | 10 ++++------
>   1 file changed, 4 insertions(+), 6 deletions(-)
> 
> diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
> index acf3d3fa4363..ed247195a20c 100644
> --- a/fs/f2fs/segment.c
> +++ b/fs/f2fs/segment.c
> @@ -620,12 +620,11 @@ int f2fs_create_flush_cmd_control(struct f2fs_sb_info *sbi)
>   {
>   	dev_t dev = sbi->sb->s_bdev->bd_dev;
>   	struct flush_cmd_control *fcc;
> -	int err = 0;
>   
>   	if (SM_I(sbi)->fcc_info) {
>   		fcc = SM_I(sbi)->fcc_info;
>   		if (fcc->f2fs_issue_flush)
> -			return err;
> +			return 0;
>   		goto init_thread;
>   	}
>   
> @@ -638,19 +637,18 @@ int f2fs_create_flush_cmd_control(struct f2fs_sb_info *sbi)
>   	init_llist_head(&fcc->issue_list);
>   	SM_I(sbi)->fcc_info = fcc;
>   	if (!test_opt(sbi, FLUSH_MERGE))
> -		return err;
> +		return 0;
>   
>   init_thread:
>   	fcc->f2fs_issue_flush = kthread_run(issue_flush_thread, sbi,
>   				"f2fs_flush-%u:%u", MAJOR(dev), MINOR(dev));
>   	if (IS_ERR(fcc->f2fs_issue_flush)) {
> -		err = PTR_ERR(fcc->f2fs_issue_flush);
>   		kfree(fcc);
>   		SM_I(sbi)->fcc_info = NULL;
> -		return err;
> +		return PTR_ERR(fcc->f2fs_issue_flush);

It will cause use-after-free issue.

Thanks,

>   	}
>   
> -	return err;
> +	return 0;
>   }
>   
>   void f2fs_destroy_flush_cmd_control(struct f2fs_sb_info *sbi, bool free)