[Devel] Re: PATCH -mm] fix create_new_namespaces() return value

[Cedric Le Goater]

Badari Pulavarty wrote:
> 
> 
> Cedric Le Goater wrote:
> 
>> The following patch modifies create_new_namespaces() to also use the
>> errors returned by the copy_*_ns routines and not to systematically
>> return ENOMEM.
>>
> 
> In my initial version, I did same. It doesn't work :(
> 
> copy_*_ns() routines doesn't return any errors. All they return is NULL
> in case of a
> failure + with the exception of copy_mnt_ns, there are no other failure
> cases.
> So, there is no way to find out why the copy_*_ns() routines failed from
> create_new_namespaces().
> If you really really want to do this, change all copy_*_ns() routines to
> returns meaningful
> errors instead of NULL.

Here's a second try to apply on top of -mm branch,

Thanks for the review Badari.

C. 


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

Changes since [try #1]:
        - fixed return values of clone_*_ns() routines
 
Signed-off-by: Cedric Le Goater <clg at fr.ibm.com>
Cc: Serge E. Hallyn <serue at us.ibm.com>
Cc: Badari Pulavarty <pbadari at us.ibm.com>
Cc: Pavel Emelianov <xemul at openvz.org>
Cc: Herbert Poetzl <herbert at 13thfloor.at>
Cc: Eric W. Biederman <ebiederm at xmission.com>
---
 fs/namespace.c          |    4 ++--
 kernel/nsproxy.c        |   23 +++++++++++++++++------
 kernel/user_namespace.c |    6 +++---
 kernel/utsname.c        |   10 ++++++----
 4 files changed, 28 insertions(+), 15 deletions(-)

Index: 2.6.22-rc4-mm2/kernel/nsproxy.c
===================================================================
--- 2.6.22-rc4-mm2.orig/kernel/nsproxy.c
+++ 2.6.22-rc4-mm2/kernel/nsproxy.c
@@ -58,30 +58,41 @@ static struct nsproxy *create_new_namesp
 			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);
 }
 
 /*
Index: 2.6.22-rc4-mm2/fs/namespace.c
===================================================================
--- 2.6.22-rc4-mm2.orig/fs/namespace.c
+++ 2.6.22-rc4-mm2/fs/namespace.c
@@ -1599,7 +1599,7 @@ static struct mnt_namespace *dup_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);
@@ -1613,7 +1613,7 @@ static struct mnt_namespace *dup_mnt_ns(
 	if (IS_ERR(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);
Index: 2.6.22-rc4-mm2/kernel/user_namespace.c
===================================================================
--- 2.6.22-rc4-mm2.orig/kernel/user_namespace.c
+++ 2.6.22-rc4-mm2/kernel/user_namespace.c
@@ -34,7 +34,7 @@ static struct user_namespace *clone_user
 
 	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->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
 	if (!new_user) {
 		free_uid(ns->root_user);
 		kfree(ns);
-		return NULL;
+		return ERR_PTR(-ENOMEM);
 	}
 
 	switch_uid(new_user);
Index: 2.6.22-rc4-mm2/kernel/utsname.c
===================================================================
--- 2.6.22-rc4-mm2.orig/kernel/utsname.c
+++ 2.6.22-rc4-mm2/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_n
 	struct uts_namespace *ns;
 
 	ns = kmalloc(sizeof(struct uts_namespace), GFP_KERNEL);
-	if (ns) {
-		memcpy(&ns->name, &old_ns->name, sizeof(ns->name));
-		kref_init(&ns->kref);
-	}
+	if (!ns)
+		return ERR_PTR(-ENOMEM);
+
+	memcpy(&ns->name, &old_ns->name, sizeof(ns->name));
+	kref_init(&ns->kref);
 	return ns;
 }
 
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