The mount namespace is a little tricky as an arbitrary
decision must be made about what to set fs->root and
fs->pwd to, as there is no expectation of a relationship
between the two mount namespaces.
Therefor I arbitrary find the root mount point, and follow
every mount on top of it to find the top of the mount stack.
Then I set fs->root and fs->pwd to that location.
The topmost root of the mount stack seems like a reasonable place to be.
Signed-off-by: Eric W. Biederman <ebiederm@xxxxxxxxxxxx>
---
fs/namespace.c | 57 +++++++++++++++++++++++++++++++++++++++++++++++
fs/proc/namespaces.c | 1 +
include/linux/proc_fs.h | 1 +
3 files changed, 59 insertions(+), 0 deletions(-)
diff --git a/fs/namespace.c b/fs/namespace.c
index a72eaab..ed11bac 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -32,6 +32,7 @@
#include <linux/idr.h>
#include <linux/fs_struct.h>
#include <linux/fsnotify.h>
+#include <linux/proc_fs.h>
#include <asm/uaccess.h>
#include <asm/unistd.h>
#include "pnode.h"
@@ -2418,3 +2419,59 @@ void put_mnt_ns(struct mnt_namespace *ns)
kfree(ns);
}
EXPORT_SYMBOL(put_mnt_ns);
+
+
+static void *mntns_get(struct task_struct *task)
+{
+ struct mnt_namespace *ns;
+ rcu_read_lock();
+ ns = task->nsproxy->mnt_ns;
+ get_mnt_ns(ns);
+ rcu_read_unlock();
+ return ns;
+}
+
+static void mntns_put(void *ns)
+{
+ put_mnt_ns(ns);
+}
+
+static int mntns_install(struct nsproxy *nsproxy, void *ns)
+{
+ struct fs_struct *fs = current->fs;
+ struct mnt_namespace *mnt_ns = ns;
+ struct path root;
+
+ if (fs->users != 1)
+ return -EINVAL;
+
+ get_mnt_ns(mnt_ns);
+ put_mnt_ns(nsproxy->mnt_ns);
+ nsproxy->mnt_ns = mnt_ns;
+
+ /* Find the root */
+ root.mnt = mnt_ns->root;
+ root.dentry = mnt_ns->root->mnt_root;
+ path_get(&root);
+ while(d_mountpoint(root.dentry) && follow_down(&root))
+ ;
+
+ /* Update the pwd and root */
+ path_get(&root);
+ path_get(&root);
+ path_put(&fs->root);
+ path_put(&fs->pwd);
+ fs->root = root;
+ fs->pwd = root;
+ path_put(&root);
+
+ return 0;
+}
+
+const struct proc_ns_operations mntns_operations = {
+ .name = PROC_NSNAME("mnt"),
+ .get = mntns_get,
+ .put = mntns_put,
+ .install = mntns_install,
+};
+
diff --git a/fs/proc/namespaces.c b/fs/proc/namespaces.c
index 2f503b5..c5956ad 100644
--- a/fs/proc/namespaces.c
+++ b/fs/proc/namespaces.c
@@ -25,6 +25,7 @@ static const struct proc_ns_operations *ns_entries[] = {
#ifdef CONFIG_IPC_NS
&ipcns_operations,
#endif
+ &mntns_operations,
};
static const struct file_operations ns_file_operations = {
diff --git a/include/linux/proc_fs.h b/include/linux/proc_fs.h
index 9a9ef31..8a260b0 100644
--- a/include/linux/proc_fs.h
+++ b/include/linux/proc_fs.h
@@ -265,6 +265,7 @@ struct proc_ns_operations {
extern const struct proc_ns_operations netns_operations;
extern const struct proc_ns_operations utsns_operations;
extern const struct proc_ns_operations ipcns_operations;
+extern const struct proc_ns_operations mntns_operations;
extern struct file *proc_ns_fget(int fd);
union proc_op {
--
1.6.5.2.143.g8cc62
--
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