Hi,

sys_clone() and sys_clone() both makes copies of nsproxy
and its associated namespaces. But they have different
code paths. 

This patch merges all the nsproxy and its associated
namespace copy/clone handling (as much as possible).
Posted on container list earlier for feedback.

Ran LTP and unshare tests fine.

Andrew, can you include it in -mm ?

Thanks,
Badari



Merge sys_clone/sys_unshare nsproxy and namespace copy handling.

- Create a new nsproxy and its associated namespaces and pass it
back to caller to attach it to right process.

- Changed all copy_*_ns() routines to return a new copy of namespace
instead of attaching it to task->nsproxy.

- Moved the CAP_SYS_ADMIN checks out of copy_*_ns() routines.

- Removed unnessary !ns checks from copy_*_ns() and added BUG_ON()
  just incase.

- Get rid of all individual unshare_*_ns() routines and make
use of copy_*_ns() instead.


Signed-off-by: Badari Pulavarty <pbadari@us.ibm.com>
Cc: Cedric Le Goater <clg@fr.ibm.com>
Cc: Serge Hallyn <serue@us.ibm.com>
Cc: containers@lists.osdl.org
---
 fs/namespace.c                |   30 ++-------
 include/linux/ipc.h           |    9 +-
 include/linux/mnt_namespace.h |    5 -
 include/linux/nsproxy.h       |    2 
 include/linux/pid_namespace.h |    2 
 include/linux/utsname.h       |   17 -----
 ipc/util.c                    |   47 ++------------
 kernel/fork.c                 |   85 +------------------------
 kernel/nsproxy.c              |  139 +++++++++++++++++++++++++-----------------
 kernel/pid.c                  |   11 ---
 kernel/utsname.c              |   41 +-----------
 11 files changed, 125 insertions(+), 263 deletions(-)

Index: linux-2.6.21-rc2/fs/namespace.c
===================================================================
--- linux-2.6.21-rc2.orig/fs/namespace.c	2007-02-27 20:59:12.000000000 -0800
+++ linux-2.6.21-rc2/fs/namespace.c	2007-03-01 08:29:15.000000000 -0800
@@ -1441,10 +1441,9 @@ dput_out:
  * Allocate a new namespace structure and populate it with contents
  * copied from the namespace of the passed in task structure.
  */
-struct mnt_namespace *dup_mnt_ns(struct task_struct *tsk,
+static struct mnt_namespace *dup_mnt_ns(struct mnt_namespace *mnt_ns,
 		struct fs_struct *fs)
 {
-	struct mnt_namespace *mnt_ns = tsk->nsproxy->mnt_ns;
 	struct mnt_namespace *new_ns;
 	struct vfsmount *rootmnt = NULL, *pwdmnt = NULL, *altrootmnt = NULL;
 	struct vfsmount *p, *q;
@@ -1509,36 +1508,21 @@ struct mnt_namespace *dup_mnt_ns(struct 
 	return new_ns;
 }
 
-int copy_mnt_ns(int flags, struct task_struct *tsk)
+struct mnt_namespace *copy_mnt_ns(int flags, struct mnt_namespace *ns,
+		struct fs_struct *new_fs)
 {
-	struct mnt_namespace *ns = tsk->nsproxy->mnt_ns;
 	struct mnt_namespace *new_ns;
-	int err = 0;
-
-	if (!ns)
-		return 0;
 
+	BUG_ON(!ns);
 	get_mnt_ns(ns);
 
 	if (!(flags & CLONE_NEWNS))
-		return 0;
+		return ns;
 
-	if (!capable(CAP_SYS_ADMIN)) {
-		err = -EPERM;
-		goto out;
-	}
+	new_ns = dup_mnt_ns(ns, new_fs);
 
-	new_ns = dup_mnt_ns(tsk, tsk->fs);
-	if (!new_ns) {
-		err = -ENOMEM;
-		goto out;
-	}
-
-	tsk->nsproxy->mnt_ns = new_ns;
-
-out:
 	put_mnt_ns(ns);
-	return err;
+	return new_ns;
 }
 
 asmlinkage long sys_mount(char __user * dev_name, char __user * dir_name,
Index: linux-2.6.21-rc2/include/linux/mnt_namespace.h
===================================================================
--- linux-2.6.21-rc2.orig/include/linux/mnt_namespace.h	2007-02-27 20:59:12.000000000 -0800
+++ linux-2.6.21-rc2/include/linux/mnt_namespace.h	2007-03-01 08:29:15.000000000 -0800
@@ -14,10 +14,9 @@ struct mnt_namespace {
 	int event;
 };
 
-extern int copy_mnt_ns(int, struct task_struct *);
-extern void __put_mnt_ns(struct mnt_namespace *ns);
-extern struct mnt_namespace *dup_mnt_ns(struct task_struct *,
+extern struct mnt_namespace *copy_mnt_ns(int, struct mnt_namespace *,
 		struct fs_struct *);
+extern void __put_mnt_ns(struct mnt_namespace *ns);
 
 static inline void put_mnt_ns(struct mnt_namespace *ns)
 {
Index: linux-2.6.21-rc2/kernel/nsproxy.c
===================================================================
--- linux-2.6.21-rc2.orig/kernel/nsproxy.c	2007-02-27 20:59:12.000000000 -0800
+++ linux-2.6.21-rc2/kernel/nsproxy.c	2007-03-01 08:29:15.000000000 -0800
@@ -38,10 +38,8 @@ void get_task_namespaces(struct task_str
 
 /*
  * creates a copy of "orig" with refcount 1.
- * This does not grab references to the contained namespaces,
- * so that needs to be done by dup_namespaces.
  */
-static inline struct nsproxy *clone_namespaces(struct nsproxy *orig)
+static inline struct nsproxy *clone_nsproxy(struct nsproxy *orig)
 {
 	struct nsproxy *ns;
 
@@ -52,26 +50,49 @@ static inline struct nsproxy *clone_name
 }
 
 /*
- * copies the nsproxy, setting refcount to 1, and grabbing a
- * reference to all contained namespaces.  Called from
- * sys_unshare()
+ * Create new nsproxy and all of its the associated namespaces.
+ * Return the newly created nsproxy.  Do not attach this to the task,
+ * leave it to the caller to do proper locking and attach it to task.
  */
-struct nsproxy *dup_namespaces(struct nsproxy *orig)
+static struct nsproxy *create_new_namespaces(int flags, struct task_struct *tsk,
+			struct fs_struct *new_fs)
 {
-	struct nsproxy *ns = clone_namespaces(orig);
+	struct nsproxy *new_nsp;
 
-	if (ns) {
-		if (ns->mnt_ns)
-			get_mnt_ns(ns->mnt_ns);
-		if (ns->uts_ns)
-			get_uts_ns(ns->uts_ns);
-		if (ns->ipc_ns)
-			get_ipc_ns(ns->ipc_ns);
-		if (ns->pid_ns)
-			get_pid_ns(ns->pid_ns);
-	}
+	new_nsp = clone_nsproxy(tsk->nsproxy);
+	if (!new_nsp)
+		return ERR_PTR(-ENOMEM);
 
-	return ns;
+	new_nsp->mnt_ns = copy_mnt_ns(flags, tsk->nsproxy->mnt_ns, new_fs);
+	if (IS_ERR(new_nsp->mnt_ns))
+		goto out_ns;
+
+	new_nsp->uts_ns = copy_utsname(flags, tsk->nsproxy->uts_ns);
+	if (IS_ERR(new_nsp->uts_ns))
+		goto out_uts;
+
+	new_nsp->ipc_ns = copy_ipcs(flags, tsk->nsproxy->ipc_ns);
+	if (IS_ERR(new_nsp->ipc_ns))
+		goto out_ipc;
+
+	new_nsp->pid_ns = copy_pid_ns(flags, tsk->nsproxy->pid_ns);
+	if (IS_ERR(new_nsp->pid_ns))
+		goto out_pid;
+
+	return new_nsp;
+
+out_pid:
+	if (new_nsp->ipc_ns)
+		put_ipc_ns(new_nsp->ipc_ns);
+out_ipc:
+	if (new_nsp->uts_ns)
+		put_uts_ns(new_nsp->uts_ns);
+out_uts:
+	if (new_nsp->mnt_ns)
+		put_mnt_ns(new_nsp->mnt_ns);
+out_ns:
+	kfree(new_nsp);
+	return ERR_PTR(-ENOMEM);
 }
 
 /*
@@ -92,47 +113,21 @@ int copy_namespaces(int flags, struct ta
 	if (!(flags & (CLONE_NEWNS | CLONE_NEWUTS | CLONE_NEWIPC)))
 		return 0;
 
-	new_ns = clone_namespaces(old_ns);
-	if (!new_ns) {
-		err = -ENOMEM;
+	if (!capable(CAP_SYS_ADMIN)) {
+		err = -EPERM;
 		goto out;
 	}
 
-	tsk->nsproxy = new_ns;
-
-	err = copy_mnt_ns(flags, tsk);
-	if (err)
-		goto out_ns;
-
-	err = copy_utsname(flags, tsk);
-	if (err)
-		goto out_uts;
-
-	err = copy_ipcs(flags, tsk);
-	if (err)
-		goto out_ipc;
-
-	err = copy_pid_ns(flags, tsk);
-	if (err)
-		goto out_pid;
+	new_ns = create_new_namespaces(flags, tsk, tsk->fs);
+	if (IS_ERR(new_ns)) {
+		err = PTR_ERR(new_ns);
+		goto out;
+	}
 
+	tsk->nsproxy = new_ns;
 out:
 	put_nsproxy(old_ns);
 	return err;
-
-out_pid:
-	if (new_ns->ipc_ns)
-		put_ipc_ns(new_ns->ipc_ns);
-out_ipc:
-	if (new_ns->uts_ns)
-		put_uts_ns(new_ns->uts_ns);
-out_uts:
-	if (new_ns->mnt_ns)
-		put_mnt_ns(new_ns->mnt_ns);
-out_ns:
-	tsk->nsproxy = old_ns;
-	kfree(new_ns);
-	goto out;
 }
 
 void free_nsproxy(struct nsproxy *ns)
@@ -147,3 +142,41 @@ void free_nsproxy(struct nsproxy *ns)
 		put_pid_ns(ns->pid_ns);
 	kfree(ns);
 }
+
+/*
+ * Called from unshare. Unshare all the namespaces part of nsproxy.
+ * On sucess, returns the new nsproxy and a reference to old nsproxy
+ * to make sure it stays around.
+ */
+int unshare_nsproxy_namespaces(unsigned long unshare_flags,
+		struct nsproxy **new_nsp, struct fs_struct *new_fs)
+{
+	struct nsproxy *old_ns = current->nsproxy;
+	int err = 0;
+
+	if (!(unshare_flags & (CLONE_NEWNS | CLONE_NEWUTS | CLONE_NEWIPC)))
+		return 0;
+
+#ifndef CONFIG_IPC_NS
+	if (unshare_flags & CLONE_NEWIPC)
+		return -EINVAL;
+#endif
+
+#ifndef CONFIG_UTS_NS
+	if (unshare_flags & CLONE_NEWUTS)
+		return -EINVAL;
+#endif
+
+	if (!capable(CAP_SYS_ADMIN))
+		return -EPERM;
+
+	get_nsproxy(old_ns);
+
+	*new_nsp = create_new_namespaces(unshare_flags, current,
+				new_fs ? new_fs : current->fs);
+	if (IS_ERR(*new_nsp)) {
+		err = PTR_ERR(*new_nsp);
+		put_nsproxy(old_ns);
+	}
+	return err;
+}
Index: linux-2.6.21-rc2/include/linux/utsname.h
===================================================================
--- linux-2.6.21-rc2.orig/include/linux/utsname.h	2007-02-27 20:59:12.000000000 -0800
+++ linux-2.6.21-rc2/include/linux/utsname.h	2007-03-01 08:29:15.000000000 -0800
@@ -49,9 +49,7 @@ static inline void get_uts_ns(struct uts
 }
 
 #ifdef CONFIG_UTS_NS
-extern int unshare_utsname(unsigned long unshare_flags,
-				struct uts_namespace **new_uts);
-extern int copy_utsname(int flags, struct task_struct *tsk);
+extern struct uts_namespace *copy_utsname(int flags, struct uts_namespace *ns);
 extern void free_uts_ns(struct kref *kref);
 
 static inline void put_uts_ns(struct uts_namespace *ns)
@@ -59,18 +57,9 @@ static inline void put_uts_ns(struct uts
 	kref_put(&ns->kref, free_uts_ns);
 }
 #else
-static inline int unshare_utsname(unsigned long unshare_flags,
-			struct uts_namespace **new_uts)
+static inline int copy_utsname(int flags, struct uts_namespace *ns)
 {
-	if (unshare_flags & CLONE_NEWUTS)
-		return -EINVAL;
-
-	return 0;
-}
-
-static inline int copy_utsname(int flags, struct task_struct *tsk)
-{
-	return 0;
+	return ns;
 }
 static inline void put_uts_ns(struct uts_namespace *ns)
 {
Index: linux-2.6.21-rc2/kernel/utsname.c
===================================================================
--- linux-2.6.21-rc2.orig/kernel/utsname.c	2007-02-27 20:59:1