Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
Subject: Re: [PATCH 4.19 33/75] f2fs: fix to avoid accessing xattr across the
 boundary
To:     Pavel Machek <pavel@ucw.cz>
CC:     <linux-kernel@vger.kernel.org>,
        Randall Huang <huangrandall@google.com>,
        Jaegeuk Kim <jaegeuk@kernel.org>,
        Sasha Levin <sashal@kernel.org>
References: <20190617210752.799453599@linuxfoundation.org>
 <20190617210754.076823433@linuxfoundation.org>
 <20190619123210.GA14477@xo-6d-61-c0.localdomain>
From:   Chao Yu <yuchao0@huawei.com>
Message-ID: <d77e58a9-561d-7fbd-bee8-592c7d21df64@huawei.com>
Date:   Thu, 20 Jun 2019 09:46:35 +0800
User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:52.0) Gecko/20100101
 Thunderbird/52.9.1
MIME-Version: 1.0
In-Reply-To: <20190619123210.GA14477@xo-6d-61-c0.localdomain>
Content-Type: text/plain; charset="windows-1252"
Content-Language: en-US
Content-Transfer-Encoding: 7bit
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

Hi Pavel,

On 2019/6/19 20:32, Pavel Machek wrote:
> Hi!
> 
>> When we traverse xattr entries via __find_xattr(),
>> if the raw filesystem content is faked or any hardware failure occurs,
>> out-of-bound error can be detected by KASAN.
>> Fix the issue by introducing boundary check.
> 
> Ok, so this prevents fs corruption from causing problems,
> 
>> @@ -340,7 +347,11 @@ static int lookup_all_xattrs(struct inode *inode, struct page *ipage,
>>  	else
>>  		cur_addr = txattr_addr;
>>  
>> -	*xe = __find_xattr(cur_addr, index, len, name);
>> +	*xe = __find_xattr(cur_addr, last_txattr_addr, index, len, name);
>> +	if (!*xe) {
>> +		err = -EFAULT;
>> +		goto out;
>> +	}
> 
> Is -EFAULT suitable here? We do not have userspace passing pointers to us, we
> have fs corruption. -EUNCLEAN?

Oh, right, f2fs uses -EFAULT as error number to indicate filesystem is corrupted
all the time, we need to fix it to follow other generic fs.

> 
> Should it do some kind of printk to let the user know fs is corrupted, and mark
> it as needing fsck?

Agreed, let me add it. :)

Thanks,

> 
> Thanks,
> 									Pavel
> .
>