From mboxrd@z Thu Jan  1 00:00:00 1970
From: Tao Ma <tao.ma@oracle.com>
Subject: Re: [Patch v2] btrfs: use file_remove_suid() after i_mutex is held
Date: Mon, 06 Jul 2009 15:42:51 +0800
Message-ID: <4A51AAFB.1000601@oracle.com>
References: <20090706072043.6555.13669.sendpatchset@localhost.localdomain>
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Cc: linux-kernel@vger.kernel.org, Jeff Mahoney <jeffm@suse.com>,
	Yan Zheng <zheng.yan@oracle.com>,
	Josef Bacik <jbacik@redhat.com>, Arjan <arjan@infradead.org>,
	Chris Mason <chris.mason@oracle.com>,
	akpm@linux-foundation.org, linux-btrfs@vger.kernel.org,
	Sven Wegener <sven.wegener@stealer.net>
To: Amerigo Wang <amwang@redhat.com>
Return-path: <linux-btrfs-owner@vger.kernel.org>
In-Reply-To: <20090706072043.6555.13669.sendpatchset@localhost.localdomain>
List-ID: <linux-btrfs.vger.kernel.org>

Hi Amerigo,

Amerigo Wang wrote:
> V1 -> V2:
> Move kmalloc() before mutex_lock(), suggested by Arjan.
> 
> file_remove_suid() should be called with i_mutex held,
> file_update_time() too. So move them after mutex_lock().
> 
> Plus, check the return value of kmalloc().
> 
> Signed-off-by: WANG Cong <amwang@redhat.com>
> Cc: Arjan <arjan@infradead.org>
> Cc: Chris Mason <chris.mason@oracle.com>
> Cc: Yan Zheng <zheng.yan@oracle.com>
> Cc: Sven Wegener <sven.wegener@stealer.net>
> Cc: Josef Bacik <jbacik@redhat.com>
> Cc: Jeff Mahoney <jeffm@suse.com>
> 
> ---
> diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c
> index 7c3cd24..09ef5d6 100644
> --- a/fs/btrfs/file.c
> +++ b/fs/btrfs/file.c
> @@ -944,14 +944,17 @@ static ssize_t btrfs_file_write(struct file *file, const char __user *buf,
>  	if (count == 0)
>  		goto out_nolock;
>  
> +	pages = kmalloc(nrptrs * sizeof(struct page *), GFP_KERNEL);
> +	if (!pages)
> +		goto out_nolock;
I guess you need to set err to -ENOMEM here so that the caller knows 
what's wrong. With your patch, this function just return 0(since 
num_written and err are both 0) with no error, and I guess it is worse 
than kernel BUG out when the NULL pages is used later.

Regards,
Tao