[Devel] Re: - merge-sys_clone-sys_unshare-nsproxy-and-namespace.patch removed from -mm tree

[Oleg Nesterov]

On 06/18, Cedric Le Goater wrote:
>
> Oleg Nesterov wrote:
> > On 06/17, Oleg Nesterov wrote:
> >> Let's look at copy_namespaces(), it does the same "get_xxx() in advance", but
> >> -EPERM forgets to do put_nsproxy(), so we definitely have a leak in copy_process().
> > 
> > Ugh, I am sorry, EPERM does put_nsproxy(). Still I can't understand why
> > copy_namespaces() does get_nsproxy() unconditionally.
> 
> well, if you're cloning a new task and not unsharing some of the namespaces
> you still want to increase the refcount on the nsproxy bc a new task is now
> referencing it. nop ?

Yes, but copy_namespaces() does get_nsproxy() unconditionally, and then it does
put_nsproxy() if not unsharing, which is not good imho.

IOW, I think the patch below makes the code a bit better. copy_namespaces()
doesn't need put_nsproxy() at all.

Oleg.

--- t/kernel/nsproxy.c~	2007-06-18 16:10:53.000000000 +0400
+++ t/kernel/nsproxy.c	2007-06-18 16:13:02.000000000 +0400
@@ -103,31 +103,24 @@ int copy_namespaces(int flags, struct ta
 {
 	struct nsproxy *old_ns = tsk->nsproxy;
 	struct nsproxy *new_ns;
-	int err = 0;
 
 	if (!old_ns)
 		return 0;
 
-	get_nsproxy(old_ns);
-
-	if (!(flags & (CLONE_NEWNS | CLONE_NEWUTS | CLONE_NEWIPC)))
+	if (!(flags & (CLONE_NEWNS | CLONE_NEWUTS | CLONE_NEWIPC))) {
+		get_nsproxy(old_ns);
 		return 0;
-
-	if (!capable(CAP_SYS_ADMIN)) {
-		err = -EPERM;
-		goto out;
 	}
 
+	if (!capable(CAP_SYS_ADMIN))
+		return -EPERM;
+
 	new_ns = create_new_namespaces(flags, tsk, tsk->fs);
-	if (IS_ERR(new_ns)) {
-		err = PTR_ERR(new_ns);
-		goto out;
-	}
+	if (IS_ERR(new_ns))
+		return PTR_ERR(new_ns);
 
 	tsk->nsproxy = new_ns;
-out:
-	put_nsproxy(old_ns);
-	return err;
+	return 0;
 }
 
 void free_nsproxy(struct nsproxy *ns)

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