[Devel] Re: - merge-sys_clone-sys_unshare-nsproxy-and-namespace.patch removed from -mm tree

[Cedric Le Goater]

Oleg Nesterov wrote:
> On 06/18, Cedric Le Goater wrote:
>> Oleg Nesterov wrote:
>>> On 06/17, Oleg Nesterov wrote:
>>>> Let's look at copy_namespaces(), it does the same "get_xxx() in advance", but
>>>> -EPERM forgets to do put_nsproxy(), so we definitely have a leak in copy_process().
>>> Ugh, I am sorry, EPERM does put_nsproxy(). Still I can't understand why
>>> copy_namespaces() does get_nsproxy() unconditionally.
>> well, if you're cloning a new task and not unsharing some of the namespaces
>> you still want to increase the refcount on the nsproxy bc a new task is now
>> referencing it. nop ?
> 
> Yes, but copy_namespaces() does get_nsproxy() unconditionally, and then it does
> put_nsproxy() if not unsharing, which is not good imho.
> 
> IOW, I think the patch below makes the code a bit better. copy_namespaces()
> doesn't need put_nsproxy() at all.

Indeed it does and also :

nsproxy.c |   23 ++++++++---------------
 1 file changed, 8 insertions(+), 15 deletions(-)

Thanks,

C. 

> Oleg.
> 
> --- t/kernel/nsproxy.c~	2007-06-18 16:10:53.000000000 +0400
> +++ t/kernel/nsproxy.c	2007-06-18 16:13:02.000000000 +0400
> @@ -103,31 +103,24 @@ int copy_namespaces(int flags, struct ta
>  {
>  	struct nsproxy *old_ns = tsk->nsproxy;
>  	struct nsproxy *new_ns;
> -	int err = 0;
> 
>  	if (!old_ns)
>  		return 0;
> 
> -	get_nsproxy(old_ns);
> -
> -	if (!(flags & (CLONE_NEWNS | CLONE_NEWUTS | CLONE_NEWIPC)))
> +	if (!(flags & (CLONE_NEWNS | CLONE_NEWUTS | CLONE_NEWIPC))) {
> +		get_nsproxy(old_ns);
>  		return 0;
> -
> -	if (!capable(CAP_SYS_ADMIN)) {
> -		err = -EPERM;
> -		goto out;
>  	}
> 
> +	if (!capable(CAP_SYS_ADMIN))
> +		return -EPERM;
> +
>  	new_ns = create_new_namespaces(flags, tsk, tsk->fs);
> -	if (IS_ERR(new_ns)) {
> -		err = PTR_ERR(new_ns);
> -		goto out;
> -	}
> +	if (IS_ERR(new_ns))
> +		return PTR_ERR(new_ns);
> 
>  	tsk->nsproxy = new_ns;
> -out:
> -	put_nsproxy(old_ns);
> -	return err;
> +	return 0;
>  }
> 
>  void free_nsproxy(struct nsproxy *ns)
> 
> 

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