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authorEric W. Biederman <ebiederm@xmission.com>2010-03-07 17:48:52 -0800
committerEric W. Biederman <ebiederm@xmission.com>2011-05-10 14:32:56 -0700
commit0663c6f8fa37d777ede74ff991a0cba3a42fcbd7 (patch)
tree83275d8fd4e0bcc9cb8fdde5c15bb5e4bead92fd
parent6b4e306aa3dc94a0545eb9279475b1ab6209a31f (diff)
ns: Introduce the setns syscall
With the networking stack today there is demand to handle multiple network stacks at a time. Not in the context of containers but in the context of people doing interesting things with routing. There is also demand in the context of containers to have an efficient way to execute some code in the container itself. If nothing else it is very useful ad a debugging technique. Both problems can be solved by starting some form of login daemon in the namespaces people want access to, or you can play games by ptracing a process and getting the traced process to do things you want it to do. However it turns out that a login daemon or a ptrace puppet controller are more code, they are more prone to failure, and generally they are less efficient than simply changing the namespace of a process to a specified one. Pieces of this puzzle can also be solved by instead of coming up with a general purpose system call coming up with targed system calls perhaps socketat that solve a subset of the larger problem. Overall that appears to be more work for less reward. int setns(int fd, int nstype); The fd argument is a file descriptor referring to a proc file of the namespace you want to switch the process to. In the setns system call the nstype is 0 or specifies an clone flag of the namespace you intend to change to prevent changing a namespace unintentionally. v2: Most of the architecture support added by Daniel Lezcano <dlezcano@fr.ibm.com> v3: ported to v2.6.36-rc4 by: Eric W. Biederman <ebiederm@xmission.com> v4: Moved wiring up of the system call to another patch v5: Cleaned up the system call arguments - Changed the order. - Modified nstype to take the standard clone flags. v6: Added missing error handling as pointed out by Matt Helsley <matthltc@us.ibm.com> Acked-by: Daniel Lezcano <daniel.lezcano@free.fr> Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
-rw-r--r--kernel/nsproxy.c42
1 files changed, 42 insertions, 0 deletions
diff --git a/kernel/nsproxy.c b/kernel/nsproxy.c
index a05d191ffdd9..5424e37673ed 100644
--- a/kernel/nsproxy.c
+++ b/kernel/nsproxy.c
@@ -22,6 +22,9 @@
#include <linux/pid_namespace.h>
#include <net/net_namespace.h>
#include <linux/ipc_namespace.h>
+#include <linux/proc_fs.h>
+#include <linux/file.h>
+#include <linux/syscalls.h>
static struct kmem_cache *nsproxy_cachep;
@@ -233,6 +236,45 @@ void exit_task_namespaces(struct task_struct *p)
switch_task_namespaces(p, NULL);
}
+SYSCALL_DEFINE2(setns, int, fd, int, nstype)
+{
+ const struct proc_ns_operations *ops;
+ struct task_struct *tsk = current;
+ struct nsproxy *new_nsproxy;
+ struct proc_inode *ei;
+ struct file *file;
+ int err;
+
+ if (!capable(CAP_SYS_ADMIN))
+ return -EPERM;
+
+ file = proc_ns_fget(fd);
+ if (IS_ERR(file))
+ return PTR_ERR(file);
+
+ err = -EINVAL;
+ ei = PROC_I(file->f_dentry->d_inode);
+ ops = ei->ns_ops;
+ if (nstype && (ops->type != nstype))
+ goto out;
+
+ new_nsproxy = create_new_namespaces(0, tsk, tsk->fs);
+ if (IS_ERR(new_nsproxy)) {
+ err = PTR_ERR(new_nsproxy);
+ goto out;
+ }
+
+ err = ops->install(new_nsproxy, ei->ns);
+ if (err) {
+ free_nsproxy(new_nsproxy);
+ goto out;
+ }
+ switch_task_namespaces(tsk, new_nsproxy);
+out:
+ fput(file);
+ return err;
+}
+
static int __init nsproxy_cache_init(void)
{
nsproxy_cachep = KMEM_CACHE(nsproxy, SLAB_PANIC);