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Date:   Thu, 21 Apr 2022 14:34:47 +0300
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Subject: Re: [PATCH] btrfs: Fix a memory leak in btrfs_ioctl_balance()
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From:   Nikolay Borisov <nborisov@suse.com>
To:     Haowen Bai <baihaowen@meizu.com>, Chris Mason <clm@fb.com>,
        Josef Bacik <josef@toxicpanda.com>,
        David Sterba <dsterba@suse.com>
Cc:     linux-btrfs@vger.kernel.org, linux-kernel@vger.kernel.org
References: <1650534677-31554-1-git-send-email-baihaowen@meizu.com>
 <2aeffa33-e591-acad-f96f-59cfadb5aeb2@suse.com>
 <c7d16718-1071-2b57-fc77-968945cfb4f5@suse.com>
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<snip>

> 
> Actually to simplify further:
> 
> diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
> index 7a6974e877f4..bbda55d41a06 100644
> --- a/fs/btrfs/ioctl.c
> +++ b/fs/btrfs/ioctl.c
> @@ -4353,6 +4353,7 @@ static long btrfs_ioctl_balance(struct file *file, 
> void __user *arg)
>          bargs = memdup_user(arg, sizeof(*bargs));
>          if (IS_ERR(bargs)) {
>                  ret = PTR_ERR(bargs);
> +               bargs = NULL;
>                  goto out;
>          }

Unf, this also leads to the double free ...

<snip>