linux-kernel - Re: [PATCH] ecryptfs: Fix explicit null dereference

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Message-ID: <20131114195238.GA7693@boyd>
Date:	Thu, 14 Nov 2013 11:52:43 -0800
From:	Tyler Hicks <tyhicks@...onical.com>
To:	"Geyslan G. Bem" <geyslan@...il.com>
Cc:	ecryptfs@...r.kernel.org, linux-kernel@...r.kernel.org,
	Dan Carpenter <dan.carpenter@...cle.com>,
	Pekka Enberg <penberg@...nel.org>
Subject: Re: [PATCH] ecryptfs: Fix explicit null dereference

On 2013-11-14 15:42:14, Geyslan G. Bem wrote:
> If the condition 'ecryptfs_file_to_private(file)' takes false branch
> lower_file is dereferenced when NULL.
> 
> Caught by Coverity: CIDs 1128834 and 1128833.
> 
> Signed-off-by: Geyslan G. Bem <geyslan@...il.com>
> ---

Hello - Smatch picked up on this earlier in week and Dan analyzed the
situation here:

  http://article.gmane.org/gmane.comp.file-systems.ecryptfs.general/441

I agree with his assessment and proposed the following patch:

  http://article.gmane.org/gmane.comp.file-systems.ecryptfs.general/442

It makes Smatch happy and it should also make Coverity happy.

Tyler

>  fs/ecryptfs/file.c | 12 ++++++++----
>  1 file changed, 8 insertions(+), 4 deletions(-)
> 
> diff --git a/fs/ecryptfs/file.c b/fs/ecryptfs/file.c
> index 2229a74..1c0403a 100644
> --- a/fs/ecryptfs/file.c
> +++ b/fs/ecryptfs/file.c
> @@ -316,10 +316,12 @@ ecryptfs_unlocked_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
>  	struct file *lower_file = NULL;
>  	long rc = -ENOTTY;
>  
> -	if (ecryptfs_file_to_private(file))
> -		lower_file = ecryptfs_file_to_lower(file);
> +	if (!ecryptfs_file_to_private(file))
> +		goto out;
> +	lower_file = ecryptfs_file_to_lower(file);
>  	if (lower_file->f_op->unlocked_ioctl)
>  		rc = lower_file->f_op->unlocked_ioctl(lower_file, cmd, arg);
> +out:
>  	return rc;
>  }
>  
> @@ -330,10 +332,12 @@ ecryptfs_compat_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
>  	struct file *lower_file = NULL;
>  	long rc = -ENOIOCTLCMD;
>  
> -	if (ecryptfs_file_to_private(file))
> -		lower_file = ecryptfs_file_to_lower(file);
> +	if (!ecryptfs_file_to_private(file))
> +		goto out;
> +	lower_file = ecryptfs_file_to_lower(file);
>  	if (lower_file->f_op && lower_file->f_op->compat_ioctl)
>  		rc = lower_file->f_op->compat_ioctl(lower_file, cmd, arg);
> +out:
>  	return rc;
>  }
>  #endif
> -- 
> 1.8.4.2
> 
> --
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