fix create_new_namespaces() return value

dup_mnt_ns() and clone_uts_ns() return NULL on failure.  This is wrong,
create_new_namespaces() uses ERR_PTR() to catch an error.  This means that the
subsequent create_new_namespaces() will hit BUG_ON() in copy_mnt_ns() or
copy_utsname().

Modify create_new_namespaces() to also use the errors returned by the
copy_*_ns routines and not to systematically return ENOMEM.

[oleg@tv-sign.ru: better changelog]
Signed-off-by: Cedric Le Goater <clg@fr.ibm.com>
Cc: Serge E. Hallyn <serue@us.ibm.com>
Cc: Badari Pulavarty <pbadari@us.ibm.com>
Cc: Pavel Emelianov <xemul@openvz.org>
Cc: Herbert Poetzl <herbert@13thfloor.at>
Cc: Eric W. Biederman <ebiederm@xmission.com>
Cc: Oleg Nesterov <oleg@tv-sign.ru>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

fs/namespace.c

@@ -1451,7 +1451,7 @@ static struct mnt_namespace *dup_mnt_ns(struct mnt_namespace *mnt_ns,
 
 	new_ns = kmalloc(sizeof(struct mnt_namespace), GFP_KERNEL);
 	if (!new_ns)
-		return NULL;
+		return ERR_PTR(-ENOMEM);
 
 	atomic_set(&new_ns->count, 1);
 	INIT_LIST_HEAD(&new_ns->list);
@@ -1465,7 +1465,7 @@ static struct mnt_namespace *dup_mnt_ns(struct mnt_namespace *mnt_ns,
 	if (!new_ns->root) {
 		up_write(&namespace_sem);
 		kfree(new_ns);
-		return NULL;
+		return ERR_PTR(-ENOMEM);;
 	}
 	spin_lock(&vfsmount_lock);
 	list_add_tail(&new_ns->list, &new_ns->root->mnt_list);

kernel/nsproxy.c

@@ -58,30 +58,41 @@ static struct nsproxy *create_new_namespaces(int flags, struct task_struct *tsk,
 			struct fs_struct *new_fs)
 {
 	struct nsproxy *new_nsp;
+	int err;
 
 	new_nsp = clone_nsproxy(tsk->nsproxy);
 	if (!new_nsp)
 		return ERR_PTR(-ENOMEM);
 
 	new_nsp->mnt_ns = copy_mnt_ns(flags, tsk->nsproxy->mnt_ns, new_fs);
-	if (IS_ERR(new_nsp->mnt_ns))
+	if (IS_ERR(new_nsp->mnt_ns)) {
+		err = PTR_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))
+	if (IS_ERR(new_nsp->uts_ns)) {
+		err = PTR_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))
+	if (IS_ERR(new_nsp->ipc_ns)) {
+		err = PTR_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))
+	if (IS_ERR(new_nsp->pid_ns)) {
+		err = PTR_ERR(new_nsp->pid_ns);
 		goto out_pid;
+	}
 
 	new_nsp->user_ns = copy_user_ns(flags, tsk->nsproxy->user_ns);
-	if (IS_ERR(new_nsp->user_ns))
+	if (IS_ERR(new_nsp->user_ns)) {
+		err = PTR_ERR(new_nsp->user_ns);
 		goto out_user;
+	}
 
 	return new_nsp;
 
@@ -99,7 +110,7 @@ out_uts:
 		put_mnt_ns(new_nsp->mnt_ns);
 out_ns:
 	kfree(new_nsp);
-	return ERR_PTR(-ENOMEM);
+	return ERR_PTR(err);
 }
 
 /*

kernel/user_namespace.c

@@ -34,7 +34,7 @@ static struct user_namespace *clone_user_ns(struct user_namespace *old_ns)
 
 	ns = kmalloc(sizeof(struct user_namespace), GFP_KERNEL);
 	if (!ns)
-		return NULL;
+		return ERR_PTR(-ENOMEM);
 
 	kref_init(&ns->kref);
 
@@ -45,7 +45,7 @@ static struct user_namespace *clone_user_ns(struct user_namespace *old_ns)
 	ns->root_user = alloc_uid(ns, 0);
 	if (!ns->root_user) {
 		kfree(ns);
-		return NULL;
+		return ERR_PTR(-ENOMEM);
 	}
 
 	/* Reset current->user with a new one */
@@ -53,7 +53,7 @@ static struct user_namespace *clone_user_ns(struct user_namespace *old_ns)
 	if (!new_user) {
 		free_uid(ns->root_user);
 		kfree(ns);
-		return NULL;
+		return ERR_PTR(-ENOMEM);
 	}
 
 	switch_uid(new_user);

kernel/utsname.c

@@ -13,6 +13,7 @@
 #include <linux/uts.h>
 #include <linux/utsname.h>
 #include <linux/version.h>
+#include <linux/err.h>
 
 /*
  * Clone a new ns copying an original utsname, setting refcount to 1
@@ -24,10 +25,11 @@ static struct uts_namespace *clone_uts_ns(struct uts_namespace *old_ns)
 	struct uts_namespace *ns;
 
 	ns = kmalloc(sizeof(struct uts_namespace), GFP_KERNEL);
-	if (ns) {
+	if (!ns)
+		return ERR_PTR(-ENOMEM);
+
 	memcpy(&ns->name, &old_ns->name, sizeof(ns->name));
 	kref_init(&ns->kref);
-	}
 	return ns;
 }