Re: [patch 12/12] vfs: allow file truncations when both suid and write permissions set

[Amerigo Wang <amwang@redhat.com>]

OGAWA Hirofumi wrote:
> akpm@linux-foundation.org writes:
>
>   
>> diff -puN fs/open.c~vfs-allow-file-truncations-when-both-suid-and-write-permissions-set fs/open.c
>> --- a/fs/open.c~vfs-allow-file-truncations-when-both-suid-and-write-permissions-set
>> +++ a/fs/open.c
>> @@ -213,11 +213,15 @@ int do_truncate(struct dentry *dentry, l
>>  		newattrs.ia_valid |= ATTR_FILE;
>>  	}
>>  
>> +	mutex_lock(&dentry->d_inode->i_mutex);
>>  	/* Remove suid/sgid on truncate too */
>> -	newattrs.ia_valid |= should_remove_suid(dentry);
>> +	err = dentry_remove_suid(dentry);
>> +	if (err)
>> +		goto unlock;
>>     
>
> Can't we use ATTR_FORCE for this? Because this calls notify_change()
> twice, and I guess this removes s[ug]id even if vmtruncate() (or in
> future ->truncate() may return error) or something returned error.
>
> I think it would not be good behavior.
>   

Hi, please check:
http://lkml.org/lkml/2009/7/1/459