Re: [PATCH 4.19 33/75] f2fs: fix to avoid accessing xattr across the boundary

[Chao Yu]

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
> .
>