linux-kernel - Re: [Patch] btrfs: use file_remove_suid() after i

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Message-ID: <4A5198A0.6030904@redhat.com>
Date:	Mon, 06 Jul 2009 14:24:32 +0800
From:	Amerigo Wang <amwang@...hat.com>
To:	Arjan van de Ven <arjan@...radead.org>
CC:	linux-kernel@...r.kernel.org, Jeff Mahoney <jeffm@...e.com>,
	Yan Zheng <zheng.yan@...cle.com>,
	Josef Bacik <jbacik@...hat.com>,
	Chris Mason <chris.mason@...cle.com>,
	akpm@...ux-foundation.org, linux-btrfs@...r.kernel.org,
	Sven Wegener <sven.wegener@...aler.net>
Subject: Re: [Patch] btrfs: use file_remove_suid() after i_mutex is held

Arjan van de Ven wrote:
> On Mon, 6 Jul 2009 01:29:14 -0400
> Amerigo Wang <amwang@...hat.com> wrote:
>
>   
>> 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@...hat.com>
>>
>> ---
>> diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c
>> index 7c3cd24..cd36301 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;
>>  
>> +	mutex_lock(&inode->i_mutex);
>> +
>>  	err = file_remove_suid(file);
>>  	if (err)
>> -		goto out_nolock;
>> +		goto out;
>>  	file_update_time(file);
>>  
>>  	pages = kmalloc(nrptrs * sizeof(struct page *), GFP_KERNEL);
>> +	if (!pages)
>> +		goto out;
>>  
>>     
> Hi,
>
> I don't think you can keep this at GFP_KERNEL once you hold i_mutex....
> very likely this needs to now turn into GFP_NOFS!
>   

Good point!
Hmm,  GFP_KERNEL adds __GFP_FS while GFP_NOFS not...
Just moving that kmalloc() up, before mutex_lock(), I think, can solve
this.

I will update this patch now...

Thanks!

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