NFS: Fix /proc/fs/nfsfs/servers and /proc/fs/nfsfs/volumes

The usage of pid_ns->child_reaper->nsproxy->net_ns in
nfs_server_list_open and nfs_client_list_open is not safe.

/proc for a pid namespace can remain mounted after the all of the
process in that pid namespace have exited.  There are also times
before the initial process in a pid namespace has started or after the
initial process in a pid namespace has exited where
pid_ns->child_reaper can be NULL or stale.  Making the idiom
pid_ns->child_reaper->nsproxy a double whammy of problems.

Luckily all that needs to happen is to move /proc/fs/nfsfs/servers and
/proc/fs/nfsfs/volumes under /proc/net to /proc/net/nfsfs/servers and
/proc/net/nfsfs/volumes and add a symlink from the original location,
and to use seq_open_net as it has been designed.

Cc: stable@vger.kernel.org
Cc: Trond Myklebust <trond.myklebust@primarydata.com>
Cc: Stanislav Kinsbursky <skinsbursky@parallels.com>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>

1 files changed, 55 insertions, 40 deletions

diff --git a/fs/nfs/client.c b/fs/nfs/client.c
index 1d09289c8f0e..180d1ec9c32e 100644
--- a/fs/nfs/client.c
+++ b/fs/nfs/client.c
@@ -1205,7 +1205,7 @@ static const struct file_operations nfs_server_list_fops = {
         .open           = nfs_server_list_open,
         .read           = seq_read,
         .llseek         = seq_lseek,
-        .release        = seq_release,
+        .release        = seq_release_net,
         .owner          = THIS_MODULE,
 };
 
@@ -1226,7 +1226,7 @@ static const struct file_operations nfs_volume_list_fops = {
         .open           = nfs_volume_list_open,
         .read           = seq_read,
         .llseek         = seq_lseek,
-        .release        = seq_release,
+        .release        = seq_release_net,
         .owner          = THIS_MODULE,
 };
 
@@ -1236,19 +1236,8 @@ static const struct file_operations nfs_volume_list_fops = {
  */
 static int nfs_server_list_open(struct inode *inode, struct file *file)
 {
-        struct seq_file *m;
-        int ret;
-        struct pid_namespace *pid_ns = file->f_dentry->d_sb->s_fs_info;
-        struct net *net = pid_ns->child_reaper->nsproxy->net_ns;
-
-        ret = seq_open(file, &nfs_server_list_ops);
-        if (ret < 0)
-                return ret;
-
-        m = file->private_data;
-        m->private = net;
-
-        return 0;
+        return seq_open_net(inode, file, &nfs_server_list_ops,
+                           sizeof(struct seq_net_private));
 }
 
 /*
@@ -1256,7 +1245,7 @@ static int nfs_server_list_open(struct inode *inode, struct file *file)
  */
 static void *nfs_server_list_start(struct seq_file *m, loff_t *_pos)
 {
-        struct nfs_net *nn = net_generic(m->private, nfs_net_id);
+        struct nfs_net *nn = net_generic(seq_file_net(m), nfs_net_id);
 
         /* lock the list against modification */
         spin_lock(&nn->nfs_client_lock);
@@ -1268,7 +1257,7 @@ static void *nfs_server_list_start(struct seq_file *m, loff_t *_pos)
  */
 static void *nfs_server_list_next(struct seq_file *p, void *v, loff_t *pos)
 {
-        struct nfs_net *nn = net_generic(p->private, nfs_net_id);
+        struct nfs_net *nn = net_generic(seq_file_net(p), nfs_net_id);
 
         return seq_list_next(v, &nn->nfs_client_list, pos);
 }
@@ -1278,7 +1267,7 @@ static void *nfs_server_list_next(struct seq_file *p, void *v, loff_t *pos)
  */
 static void nfs_server_list_stop(struct seq_file *p, void *v)
 {
-        struct nfs_net *nn = net_generic(p->private, nfs_net_id);
+        struct nfs_net *nn = net_generic(seq_file_net(p), nfs_net_id);
 
         spin_unlock(&nn->nfs_client_lock);
 }
@@ -1289,7 +1278,7 @@ static void nfs_server_list_stop(struct seq_file *p, void *v)
 static int nfs_server_list_show(struct seq_file *m, void *v)
 {
         struct nfs_client *clp;
-        struct nfs_net *nn = net_generic(m->private, nfs_net_id);
+        struct nfs_net *nn = net_generic(seq_file_net(m), nfs_net_id);
 
         /* display header on line 1 */
         if (v == &nn->nfs_client_list) {
@@ -1321,19 +1310,8 @@ static int nfs_server_list_show(struct seq_file *m, void *v)
  */
 static int nfs_volume_list_open(struct inode *inode, struct file *file)
 {
-        struct seq_file *m;
-        int ret;
-        struct pid_namespace *pid_ns = file->f_dentry->d_sb->s_fs_info;
-        struct net *net = pid_ns->child_reaper->nsproxy->net_ns;
-
-        ret = seq_open(file, &nfs_volume_list_ops);
-        if (ret < 0)
-                return ret;
-
-        m = file->private_data;
-        m->private = net;
-
-        return 0;
+        return seq_open_net(inode, file, &nfs_server_list_ops,
+                           sizeof(struct seq_net_private));
 }
 
 /*
@@ -1341,7 +1319,7 @@ static int nfs_volume_list_open(struct inode *inode, struct file *file)
  */
 static void *nfs_volume_list_start(struct seq_file *m, loff_t *_pos)
 {
-        struct nfs_net *nn = net_generic(m->private, nfs_net_id);
+        struct nfs_net *nn = net_generic(seq_file_net(m), nfs_net_id);
 
         /* lock the list against modification */
         spin_lock(&nn->nfs_client_lock);
@@ -1353,7 +1331,7 @@ static void *nfs_volume_list_start(struct seq_file *m, loff_t *_pos)
  */
 static void *nfs_volume_list_next(struct seq_file *p, void *v, loff_t *pos)
 {
-        struct nfs_net *nn = net_generic(p->private, nfs_net_id);
+        struct nfs_net *nn = net_generic(seq_file_net(p), nfs_net_id);
 
         return seq_list_next(v, &nn->nfs_volume_list, pos);
 }
@@ -1363,7 +1341,7 @@ static void *nfs_volume_list_next(struct seq_file *p, void *v, loff_t *pos)
  */
 static void nfs_volume_list_stop(struct seq_file *p, void *v)
 {
-        struct nfs_net *nn = net_generic(p->private, nfs_net_id);
+        struct nfs_net *nn = net_generic(seq_file_net(p), nfs_net_id);
 
         spin_unlock(&nn->nfs_client_lock);
 }
@@ -1376,7 +1354,7 @@ static int nfs_volume_list_show(struct seq_file *m, void *v)
         struct nfs_server *server;
         struct nfs_client *clp;
         char dev[8], fsid[17];
-        struct nfs_net *nn = net_generic(m->private, nfs_net_id);
+        struct nfs_net *nn = net_generic(seq_file_net(m), nfs_net_id);
 
         /* display header on line 1 */
         if (v == &nn->nfs_volume_list) {
@@ -1407,6 +1385,45 @@ static int nfs_volume_list_show(struct seq_file *m, void *v)
         return 0;
 }
 
+int nfs_fs_proc_net_init(struct net *net)
+{
+        struct nfs_net *nn = net_generic(net, nfs_net_id);
+        struct proc_dir_entry *p;
+
+        nn->proc_nfsfs = proc_net_mkdir(net, "nfsfs", net->proc_net);
+        if (!nn->proc_nfsfs)
+                goto error_0;
+
+        /* a file of servers with which we're dealing */
+        p = proc_create("servers", S_IFREG|S_IRUGO,
+                        nn->proc_nfsfs, &nfs_server_list_fops);
+        if (!p)
+                goto error_1;
+
+        /* a file of volumes that we have mounted */
+        p = proc_create("volumes", S_IFREG|S_IRUGO,
+                        nn->proc_nfsfs, &nfs_volume_list_fops);
+        if (!p)
+                goto error_2;
+        return 0;
+
+error_2:
+        remove_proc_entry("servers", nn->proc_nfsfs);
+error_1:
+        remove_proc_entry("fs/nfsfs", NULL);
+error_0:
+        return -ENOMEM;
+}
+
+void nfs_fs_proc_net_exit(struct net *net)
+{
+        struct nfs_net *nn = net_generic(net, nfs_net_id);
+
+        remove_proc_entry("volumes", nn->proc_nfsfs);
+        remove_proc_entry("servers", nn->proc_nfsfs);
+        remove_proc_entry("fs/nfsfs", NULL);
+}
+
 /*
  * initialise the /proc/fs/nfsfs/ directory
  */
@@ -1419,14 +1436,12 @@ int __init nfs_fs_proc_init(void)
                 goto error_0;
 
         /* a file of servers with which we're dealing */
-        p = proc_create("servers", S_IFREG|S_IRUGO,
-                        proc_fs_nfs, &nfs_server_list_fops);
+        p = proc_symlink("servers", proc_fs_nfs, "../../net/nfsfs/servers");
         if (!p)
                 goto error_1;
 
         /* a file of volumes that we have mounted */
-        p = proc_create("volumes", S_IFREG|S_IRUGO,
-                        proc_fs_nfs, &nfs_volume_list_fops);
+        p = proc_symlink("volumes", proc_fs_nfs, "../../net/nfsfs/volumes");
         if (!p)
                 goto error_2;
         return 0;