[RFC] [PATCH 1/3] user ns: add user_namespace ptr to vfsmount

[Serge E. Hallyn]

From: Serge Hallyn <serue at us.ibm.com>
Subject: [RFC] [PATCH 1/3] user ns: add user_namespace ptr to vfsmount

Add user_namespace ptr to vfsmount, and define a helper to compare it
to the task's user_ns.

Signed-off-by: Serge E. Hallyn <serue at us.ibm.com>
---
 fs/namespace.c        |    4 ++++
 include/linux/mount.h |    2 ++
 include/linux/sched.h |   13 +++++++++++++
 3 files changed, 19 insertions(+), 0 deletions(-)

diff --git a/fs/namespace.c b/fs/namespace.c
index e199769..cfd4584 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -25,6 +25,7 @@ #include <linux/namei.h>
 #include <linux/security.h>
 #include <linux/mount.h>
 #include <linux/ramfs.h>
+#include <linux/user.h>
 #include <asm/uaccess.h>
 #include <asm/unistd.h>
 #include "pnode.h"
@@ -56,6 +57,8 @@ struct vfsmount *alloc_vfsmnt(const char
 	struct vfsmount *mnt = kmem_cache_alloc(mnt_cache, GFP_KERNEL);
 	if (mnt) {
 		memset(mnt, 0, sizeof(struct vfsmount));
+		mnt->mnt_user_ns = current->nsproxy->user_ns;
+		get_user_ns(mnt->mnt_user_ns);
 		atomic_set(&mnt->mnt_count, 1);
 		atomic_set(&mnt->mnt_writers, 0);
 		INIT_LIST_HEAD(&mnt->mnt_hash);
@@ -109,6 +112,7 @@ void free_vfsmnt(struct vfsmount *mnt)
 	if (mnt->mnt_sb)
 		list_del(&mnt->mnt_sb_list);
 	spin_unlock(&vfsmount_lock);
+	put_user_ns(mnt->mnt_user_ns);
 	kfree(mnt->mnt_devname);
 	kmem_cache_free(mnt_cache, mnt);
 }
diff --git a/include/linux/mount.h b/include/linux/mount.h
index 8402137..827793f 100644
--- a/include/linux/mount.h
+++ b/include/linux/mount.h
@@ -21,6 +21,7 @@ struct super_block;
 struct vfsmount;
 struct dentry;
 struct mnt_namespace;
+struct user_namespace;
 
 #define MNT_NOSUID	0x01
 #define MNT_NODEV	0x02
@@ -57,6 +58,7 @@ struct vfsmount {
 	struct list_head mnt_slave;	/* slave list entry */
 	struct vfsmount *mnt_master;	/* slave is on master->mnt_slave_list */
 	struct mnt_namespace *mnt_ns;	/* containing namespace */
+	struct user_namespace *mnt_user_ns; /* namespace for uid interpretation */
 	int mnt_pinned;
 };
 
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 47fbd23..b72357d 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -82,6 +82,8 @@ #include <linux/param.h>
 #include <linux/resource.h>
 #include <linux/timer.h>
 #include <linux/hrtimer.h>
+#include <linux/nsproxy.h>
+#include <linux/mount.h>
 
 #include <asm/processor.h>
 
@@ -1583,6 +1585,17 @@ extern int cond_resched(void);
 extern int cond_resched_lock(spinlock_t * lock);
 extern int cond_resched_softirq(void);
 
+static inline int task_mnt_same_uid(struct task_struct *tsk,
+					struct vfsmount *mnt)
+{
+	if (tsk->nsproxy == init_task.nsproxy)
+		return 1;
+	if (mnt->mnt_user_ns == tsk->nsproxy->user_ns);
+		return 1;
+	return 0;
+}
+
+
 /*
  * Does a critical section need to be broken due to another
  * task waiting?:
-- 
1.4.1