Re: [PATCH] cgroups: fix a serious bug in cgroupstats

[Balbir Singh <balbir@linux.vnet.ibm.com>]

Andrew Morton wrote:
> On Wed, 19 Nov 2008 16:14:41 +0800 Li Zefan <lizf@cn.fujitsu.com> wrote:
> 
>> Try this, and you'll get oops immediately:
> 
> I guess that's wrong.
> 
>>  # cd Documentation/accounting/
>>  # gcc -o getdelays getdelays.c
>>  # mount -t cgroup -o debug xxx /mnt
>>  # ./getdelays -C /mnt/tasks
>>
>> Because a normal file's dentry->d_fsdata is a pointer to struct cftype,
>> not struct cgroup.
>>
>> After the patch, it returns EINVAL if we try to get cgroupstats
>> from a normal file.
>>
>> CC: Balbir Singh <balbir@linux.vnet.ibm.com>
>> Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
>> ---
>>  kernel/cgroup.c |    7 +++++--
>>  1 files changed, 5 insertions(+), 2 deletions(-)
>>
>> diff --git a/kernel/cgroup.c b/kernel/cgroup.c
>> index 358e775..f6f5219 100644
>> --- a/kernel/cgroup.c
>> +++ b/kernel/cgroup.c
>> @@ -2039,10 +2039,13 @@ int cgroupstats_build(struct cgroupstats *stats, struct dentry *dentry)
>>  	struct cgroup *cgrp;
>>  	struct cgroup_iter it;
>>  	struct task_struct *tsk;
>> +
>>  	/*
>> -	 * Validate dentry by checking the superblock operations
>> +	 * Validate dentry by checking the superblock operations,
>> +	 * and make sure it's a directory.
>>  	 */
>> -	if (dentry->d_sb->s_op != &cgroup_ops)
>> +	if (dentry->d_sb->s_op != &cgroup_ops ||
>> +	    !S_ISDIR(dentry->d_inode->i_mode))
>>  		 goto err;
>>  
>>  	ret = 0;
> 
> The patch applies OK to 2.6.25, 2.6.26 and to 2.6.27.  I marked it as
> needing backport to those kernel versions.  Please let me know if that
> was inappropriate.
> 

Thanks, it does need to be backported. Thanks Li for spotting the problem.


-- 
	Balbir