vfs: Pass data, ns, and ns->userns to mount_ns

Today what is normally called data (the mount options) is not passed
to fill_super through mount_ns.

Pass the mount options and the namespace separately to mount_ns so
that filesystems such as proc that have mount options, can use
mount_ns.

Pass the user namespace to mount_ns so that the standard permission
check that verifies the mounter has permissions over the namespace can
be performed in mount_ns instead of in each filesystems .mount method.
Thus removing the duplication between mqueuefs and proc in terms of
permission checks.  The extra permission check does not currently
affect the rpc_pipefs filesystem and the nfsd filesystem as those
filesystems do not currently allow unprivileged mounts.  Without
unpvileged mounts it is guaranteed that the caller has already passed
capable(CAP_SYS_ADMIN) which guarantees extra permission check will
pass.

Update rpc_pipefs and the nfsd filesystem to ensure that the network
namespace reference is always taken in fill_super and always put in kill_sb
so that the logic is simpler and so that errors originating inside of
fill_super do not cause a network namespace leak.

Acked-by: Seth Forshee <seth.forshee@canonical.com>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>

diff --git a/fs/nfsd/nfsctl.c b/fs/nfsd/nfsctl.c
index 9690cb4dd5887b020ffc897ba93888f302db3a56..5a6ae2522266bf43b2741f2a821b806fb23b3579 100644 (file)
--- a/fs/nfsd/nfsctl.c
+++ b/fs/nfsd/nfsctl.c
@@ -1154,20 +1154,15 @@ static int nfsd_fill_super(struct super_block * sb, void * data, int silent)
 #endif
                /* last one */ {""}
        };
-       struct net *net = data;
-       int ret;
-
-       ret = simple_fill_super(sb, 0x6e667364, nfsd_files);
-       if (ret)
-               return ret;
-       sb->s_fs_info = get_net(net);
-       return 0;
+       get_net(sb->s_fs_info);
+       return simple_fill_super(sb, 0x6e667364, nfsd_files);
 }
 
 static struct dentry *nfsd_mount(struct file_system_type *fs_type,
        int flags, const char *dev_name, void *data)
 {
-       return mount_ns(fs_type, flags, current->nsproxy->net_ns, nfsd_fill_super);
+       struct net *net = current->nsproxy->net_ns;
+       return mount_ns(fs_type, flags, data, net, net->user_ns, nfsd_fill_super);
 }
 
 static void nfsd_umount(struct super_block *sb)

diff --git a/fs/super.c b/fs/super.c
index d78b9847e6cbc63f0f74231cf58519a98e38a35d..fd65667832e568bce0aa1c133031297bb02dc255 100644 (file)
--- a/fs/super.c
+++ b/fs/super.c
@@ -918,12 +918,19 @@ static int ns_set_super(struct super_block *sb, void *data)
        return set_anon_super(sb, NULL);
 }
 
-struct dentry *mount_ns(struct file_system_type *fs_type, int flags,
-       void *data, int (*fill_super)(struct super_block *, void *, int))
+struct dentry *mount_ns(struct file_system_type *fs_type,
+       int flags, void *data, void *ns, struct user_namespace *user_ns,
+       int (*fill_super)(struct super_block *, void *, int))
 {
        struct super_block *sb;
 
-       sb = sget(fs_type, ns_test_super, ns_set_super, flags, data);
+       /* Don't allow mounting unless the caller has CAP_SYS_ADMIN
+        * over the namespace.
+        */
+       if (!(flags & MS_KERNMOUNT) && !ns_capable(user_ns, CAP_SYS_ADMIN))
+               return ERR_PTR(-EPERM);
+
+       sb = sget(fs_type, ns_test_super, ns_set_super, flags, ns);
        if (IS_ERR(sb))
                return ERR_CAST(sb);
 

diff --git a/include/linux/fs.h b/include/linux/fs.h
index 71988dd3af95b16c2b68a060975674dcf252cba7..1ce006a24f497ea4ff8cc620ee882bbd2454cfae 100644 (file)
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -2034,8 +2034,9 @@ struct file_system_type {
 
 #define MODULE_ALIAS_FS(NAME) MODULE_ALIAS("fs-" NAME)
 
-extern struct dentry *mount_ns(struct file_system_type *fs_type, int flags,
-       void *data, int (*fill_super)(struct super_block *, void *, int));
+extern struct dentry *mount_ns(struct file_system_type *fs_type,
+       int flags, void *data, void *ns, struct user_namespace *user_ns,
+       int (*fill_super)(struct super_block *, void *, int));
 extern struct dentry *mount_bdev(struct file_system_type *fs_type,
        int flags, const char *dev_name, void *data,
        int (*fill_super)(struct super_block *, void *, int));

diff --git a/ipc/mqueue.c b/ipc/mqueue.c
index ade739f67f1df67fc17cf631da2994eef0e3d95c..60d97082f4dcff0424a4f2a8c3d12890480ae4d2 100644 (file)
--- a/ipc/mqueue.c
+++ b/ipc/mqueue.c
@@ -305,7 +305,7 @@ err:
 static int mqueue_fill_super(struct super_block *sb, void *data, int silent)
 {
        struct inode *inode;
-       struct ipc_namespace *ns = data;
+       struct ipc_namespace *ns = sb->s_fs_info;
 
        sb->s_blocksize = PAGE_SIZE;
        sb->s_blocksize_bits = PAGE_SHIFT;
@@ -326,17 +326,14 @@ static struct dentry *mqueue_mount(struct file_system_type *fs_type,
                         int flags, const char *dev_name,
                         void *data)
 {
-       if (!(flags & MS_KERNMOUNT)) {
-               struct ipc_namespace *ns = current->nsproxy->ipc_ns;
-               /* Don't allow mounting unless the caller has CAP_SYS_ADMIN
-                * over the ipc namespace.
-                */
-               if (!ns_capable(ns->user_ns, CAP_SYS_ADMIN))
-                       return ERR_PTR(-EPERM);
-
-               data = ns;
+       struct ipc_namespace *ns;
+       if (flags & MS_KERNMOUNT) {
+               ns = data;
+               data = NULL;
+       } else {
+               ns = current->nsproxy->ipc_ns;
        }
-       return mount_ns(fs_type, flags, data, mqueue_fill_super);
+       return mount_ns(fs_type, flags, data, ns, ns->user_ns, mqueue_fill_super);
 }
 
 static void init_once(void *foo)

diff --git a/net/sunrpc/rpc_pipe.c b/net/sunrpc/rpc_pipe.c
index fc48eca21fd2edb5a4b7ef9770cd03e106956b10..84f98cbe31c3cf4ce4b19a2ca9e47f6d69783116 100644 (file)
--- a/net/sunrpc/rpc_pipe.c
+++ b/net/sunrpc/rpc_pipe.c
@@ -1386,7 +1386,7 @@ rpc_fill_super(struct super_block *sb, void *data, int silent)
 {
        struct inode *inode;
        struct dentry *root, *gssd_dentry;
-       struct net *net = data;
+       struct net *net = get_net(sb->s_fs_info);
        struct sunrpc_net *sn = net_generic(net, sunrpc_net_id);
        int err;
 
@@ -1419,7 +1419,6 @@ rpc_fill_super(struct super_block *sb, void *data, int silent)
                                           sb);
        if (err)
                goto err_depopulate;
-       sb->s_fs_info = get_net(net);
        mutex_unlock(&sn->pipefs_sb_lock);
        return 0;
 
@@ -1448,7 +1447,8 @@ static struct dentry *
 rpc_mount(struct file_system_type *fs_type,
                int flags, const char *dev_name, void *data)
 {
-       return mount_ns(fs_type, flags, current->nsproxy->net_ns, rpc_fill_super);
+       struct net *net = current->nsproxy->net_ns;
+       return mount_ns(fs_type, flags, data, net, net->user_ns, rpc_fill_super);
 }
 
 static void rpc_kill_sb(struct super_block *sb)
@@ -1468,9 +1468,9 @@ static void rpc_kill_sb(struct super_block *sb)
                                           RPC_PIPEFS_UMOUNT,
                                           sb);
        mutex_unlock(&sn->pipefs_sb_lock);
-       put_net(net);
 out:
        kill_litter_super(sb);
+       put_net(net);
 }
 
 static struct file_system_type rpc_pipe_fs_type = {