Re: [PATCH RFC v2] pidns: introduce syscall getvpid

Oleg Nesterov
2015-09-24T14:59:53Z

On 09/24, Konstantin Khlebnikov wrote:
>
> +SYSCALL_DEFINE3(getvpid, pid_t, pid, int, source, int, target)
> +{
> + struct file *source_file = NULL, *target_file = NULL;
> + struct pid_namespace *source_ns, *target_ns;
> + struct pid *struct_pid;
> + struct ns_common *ns;
> + pid_t result;
> +
> + if (source >= 0) {
> + source_file = proc_ns_fget(source);
> + result = PTR_ERR(source_file);
> + if (IS_ERR(source_file))
> + goto out;
> + ns = get_proc_ns(file_inode(source_file));
> + result = -EINVAL;
> + if (ns->ops->type != CLONE_NEWPID)
> + goto out;
> + source_ns = container_of(ns, struct pid_namespace, ns);
> + } else
> + source_ns = task_active_pid_ns(current);
> +
> + if (target >= 0) {
> + target_file = proc_ns_fget(target);
> + result = PTR_ERR(target_file);
> + if (IS_ERR(target_file))
> + goto out;
> + ns = get_proc_ns(file_inode(target_file));
> + result = -EINVAL;
> + if (ns->ops->type != CLONE_NEWPID)
> + goto out;
> + target_ns = container_of(ns, struct pid_namespace, ns);
> + } else
> + target_ns = task_active_pid_ns(current);
> +

Hmm. Eric, Konstantin, how about (uncompiled/untested) patch below
in a preparation? The code above doesn't look very readable.

In fact I think another helper

#define proc_ns_xxx(file, type) \
container_of(get_proc_ns(file_inode(file)), \
struct type, ns)

makes sense too.

Oleg.
---

diff --git a/fs/nsfs.c b/fs/nsfs.c
index 99521e7..0877dd6 100644
--- a/fs/nsfs.c
+++ b/fs/nsfs.c
@@ -118,9 +118,10 @@ int ns_get_name(char *buf, size_t size, struct task_struct *task,
return res;
}

-struct file *proc_ns_fget(int fd)
+struct file *proc_ns_fget(int fd, int nstype)
{
struct file *file;
+ struct ns_common *ns;

file = fget(fd);
if (!file)
@@ -129,6 +130,10 @@ struct file *proc_ns_fget(int fd)
if (file->f_op != &ns_file_operations)
goto out_invalid;

+ ns = get_proc_ns(file_inode(file));
+ if (nstype && (ns->ops->type != nstype))
+ goto out_invalid;
+
return file;

out_invalid:
diff --git a/include/linux/proc_ns.h b/include/linux/proc_ns.h
index 42dfc61..84c9770 100644
--- a/include/linux/proc_ns.h
+++ b/include/linux/proc_ns.h
@@ -65,7 +65,7 @@ static inline int ns_alloc_inum(struct ns_common *ns)

#define ns_free_inum(ns) proc_free_inum((ns)->inum)

-extern struct file *proc_ns_fget(int fd);
+extern struct file *proc_ns_fget(int fd, int nstype);
#define get_proc_ns(inode) ((struct ns_common *)(inode)->i_private)
extern void *ns_get_path(struct path *path, struct task_struct *task,
const struct proc_ns_operations *ns_ops);
diff --git a/kernel/nsproxy.c b/kernel/nsproxy.c
index 49746c8..fee18ba 100644
--- a/kernel/nsproxy.c
+++ b/kernel/nsproxy.c
@@ -226,21 +226,17 @@ SYSCALL_DEFINE2(setns, int, fd, int, nstype)
struct ns_common *ns;
int err;

- file = proc_ns_fget(fd);
+ file = proc_ns_fget(fd, nstype);
if (IS_ERR(file))
return PTR_ERR(file);

- err = -EINVAL;
- ns = get_proc_ns(file_inode(file));
- if (nstype && (ns->ops->type != nstype))
- goto out;
-
new_nsproxy = create_new_namespaces(0, tsk, current_user_ns(), tsk->fs);
if (IS_ERR(new_nsproxy)) {
err = PTR_ERR(new_nsproxy);
goto out;
}

+ ns = get_proc_ns(file_inode(file));
err = ns->ops->install(new_nsproxy, ns);
if (err) {
free_nsproxy(new_nsproxy);
diff --git a/net/core/net_namespace.c b/net/core/net_namespace.c
index 572af00..9dfbe68 100644
--- a/net/core/net_namespace.c
+++ b/net/core/net_namespace.c
@@ -424,15 +424,12 @@ struct net *get_net_ns_by_fd(int fd)
struct ns_common *ns;
struct net *net;

- file = proc_ns_fget(fd);
+ file = proc_ns_fget(fd, CLONE_NEWNET);
if (IS_ERR(file))
return ERR_CAST(file);

ns = get_proc_ns(file_inode(file));
- if (ns->ops == &netns_operations)
- net = get_net(container_of(ns, struct net, ns));
- else
- net = ERR_PTR(-EINVAL);
+ net = get_net(container_of(ns, struct net, ns));

fput(file);
return net;