linux-kernel - [PATCH 1/1] user namespace: fix copy_user

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Message-ID: <20070717193327.GA9101@sergelap.austin.ibm.com>
Date:	Tue, 17 Jul 2007 14:33:27 -0500
From:	"Serge E. Hallyn" <serue@...ibm.com>
To:	Sukadev Bhattiprolu <sukadev@...ibm.com>,
	Pavel Emelianov <xemul@...nvz.org>
Cc:	lkml <linux-kernel@...r.kernel.org>, Andrew Morton <akpm@...l.org>,
	containers@...ts.osdl.org, Cedric Le Goater <clg@...ibm.com>
Subject: [PATCH 1/1] user namespace: fix copy_user_ns return value

>From 32f86740d27ef77160e438cd7dc4fcd5df159dd0 Mon Sep 17 00:00:00 2001
From: Serge E. Hallyn <serue@...ibm.com>
Date: Tue, 17 Jul 2007 15:28:17 -0400
Subject: [PATCH 1/1] user namespace: fix copy_user_ns return value

When a CONFIG_USER_NS=n and a user tries to unshare some
namespace other than the user namespace, the dummy
copy_user_ns returns NULL rather than the old_ns.  This
value then gets assigned to task->nsproxy->user_ns, so
that a subsequent setuid, which uses task->nsproxy->user_ns,
causes a NULL pointer deref.

Fix this by returning old_ns.

I believe this is a bug both in -mm and mainline.

Signed-off-by: Serge E. Hallyn <serue@...ibm.com>
---
 include/linux/user_namespace.h |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/include/linux/user_namespace.h b/include/linux/user_namespace.h
index bb32057..1101b0c 100644
--- a/include/linux/user_namespace.h
+++ b/include/linux/user_namespace.h
@@ -49,7 +49,7 @@ static inline struct user_namespace *copy_user_ns(int flags,
 	if (flags & CLONE_NEWUSER)
 		return ERR_PTR(-EINVAL);
 
-	return NULL;
+	return old_ns;
 }
 
 static inline void put_user_ns(struct user_namespace *ns)
-- 
1.5.1.1.GIT

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