Re: [PATCH] Introduce and use get_task_mnt_ns()

["Serge E. Hallyn" <serge@hallyn.com>]

Quoting Alexey Dobriyan (adobriyan@openvz.org):
> Apply after "[PATCH] Fix NULL ->nsproxy dereference in /proc/*/mounts".
> 
> Similar to get_task_mm(): get a reference to task's mnt namespace if any.
> Suggested by Pavel Emelianov.
> 
> Signed-off-by: Alexey Dobriyan <adobriyan@openvz.org>

Yeah, that's nicer, thanks.

Acked-by: Serge Hallyn <serue@us.ibm.com>


> ---
> 
>  fs/proc/base.c          |   15 ++-------------
>  include/linux/nsproxy.h |    1 +
>  kernel/nsproxy.c        |   14 ++++++++++++++
>  3 files changed, 17 insertions(+), 13 deletions(-)
> 
> --- a/fs/proc/base.c
> +++ b/fs/proc/base.c
> @@ -370,13 +370,7 @@ static int mounts_open(struct inode *ino
>  	int ret = -EINVAL;
>  
>  	if (task) {
> -		task_lock(task);
> -		if (task->nsproxy) {
> -			ns = task->nsproxy->mnt_ns;
> -			if (ns)
> -				get_mnt_ns(ns);
> -		}
> -		task_unlock(task);
> +		ns = get_task_mnt_ns(task);
>  		put_task_struct(task);
>  	}
>  
> @@ -443,12 +437,7 @@ static int mountstats_open(struct inode 
>  		struct task_struct *task = get_proc_task(inode);
>  
>  		if (task) {
> -			task_lock(task);
> -			if (task->nsproxy)
> -				mnt_ns = task->nsproxy->mnt_ns;
> -			if (mnt_ns)
> -				get_mnt_ns(mnt_ns);
> -			task_unlock(task);
> +			mnt_ns = get_task_mnt_ns(task);
>  			put_task_struct(task);
>  		}
>  
> --- a/include/linux/nsproxy.h
> +++ b/include/linux/nsproxy.h
> @@ -35,6 +35,7 @@ struct nsproxy *dup_namespaces(struct ns
>  int copy_namespaces(int flags, struct task_struct *tsk);
>  void get_task_namespaces(struct task_struct *tsk);
>  void free_nsproxy(struct nsproxy *ns);
> +struct mnt_namespace * get_task_mnt_ns(struct task_struct *tsk);
>  
>  static inline void put_nsproxy(struct nsproxy *ns)
>  {
> --- a/kernel/nsproxy.c
> +++ b/kernel/nsproxy.c
> @@ -147,3 +147,17 @@ void free_nsproxy(struct nsproxy *ns)
>  		put_pid_ns(ns->pid_ns);
>  	kfree(ns);
>  }
> +
> +struct mnt_namespace * get_task_mnt_ns(struct task_struct *tsk)
> +{
> +	struct mnt_namespace *mnt_ns = NULL;
> +
> +	task_lock(tsk);
> +	if (tsk->nsproxy)
> +		mnt_ns = tsk->nsproxy->mnt_ns;
> +	if (mnt_ns)
> +		get_mnt_ns(mnt_ns);
> +	task_unlock(tsk);
> +
> +	return mnt_ns;
> +}
> 
> -
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