cifs: Check server capability before attempting silly rename

[cascardo/linux.git] / fs / namespace.c

diff --git a/fs/namespace.c b/fs/namespace.c
index 55605c5..50ca17d 100644 (file)
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -384,7 +384,7 @@ EXPORT_SYMBOL_GPL(mnt_clone_write);
  */
 int __mnt_want_write_file(struct file *file)
 {
-       struct inode *inode = file->f_dentry->d_inode;
+       struct inode *inode = file_inode(file);
 
        if (!(file->f_mode & FMODE_WRITE) || special_file(inode->i_mode))
                return __mnt_want_write(file->f_path.mnt);
@@ -1237,6 +1237,14 @@ static int do_umount(struct mount *mnt, int flags)
        return retval;
 }
 
+/* 
+ * Is the caller allowed to modify his namespace?
+ */
+static inline bool may_mount(void)
+{
+       return ns_capable(current->nsproxy->mnt_ns->user_ns, CAP_SYS_ADMIN);
+}
+
 /*
  * Now umount can handle mount points as well as block devices.
  * This is important for filesystems which use unnamed block devices.
@@ -1255,6 +1263,9 @@ SYSCALL_DEFINE2(umount, char __user *, name, int, flags)
        if (flags & ~(MNT_FORCE | MNT_DETACH | MNT_EXPIRE | UMOUNT_NOFOLLOW))
                return -EINVAL;
 
+       if (!may_mount())
+               return -EPERM;
+
        if (!(flags & UMOUNT_NOFOLLOW))
                lookup_flags |= LOOKUP_FOLLOW;
 
@@ -1268,10 +1279,6 @@ SYSCALL_DEFINE2(umount, char __user *, name, int, flags)
        if (!check_mnt(mnt))
                goto dput_and_out;
 
-       retval = -EPERM;
-       if (!ns_capable(mnt->mnt_ns->user_ns, CAP_SYS_ADMIN))
-               goto dput_and_out;
-
        retval = do_umount(mnt, flags);
 dput_and_out:
        /* we mustn't call path_put() as that would clear mnt_expiry_mark */
@@ -1293,24 +1300,6 @@ SYSCALL_DEFINE1(oldumount, char __user *, name)
 
 #endif
 
-static int mount_is_safe(struct path *path)
-{
-       if (ns_capable(real_mount(path->mnt)->mnt_ns->user_ns, CAP_SYS_ADMIN))
-               return 0;
-       return -EPERM;
-#ifdef notyet
-       if (S_ISLNK(path->dentry->d_inode->i_mode))
-               return -EPERM;
-       if (path->dentry->d_inode->i_mode & S_ISVTX) {
-               if (current_uid() != path->dentry->d_inode->i_uid)
-                       return -EPERM;
-       }
-       if (inode_permission(path->dentry->d_inode, MAY_WRITE))
-               return -EPERM;
-       return 0;
-#endif
-}
-
 static bool mnt_ns_loop(struct path *path)
 {
        /* Could bind mounting the mount namespace inode cause a
@@ -1633,9 +1622,6 @@ static int do_change_type(struct path *path, int flag)
        int type;
        int err = 0;
 
-       if (!ns_capable(mnt->mnt_ns->user_ns, CAP_SYS_ADMIN))
-               return -EPERM;
-
        if (path->dentry != path->mnt->mnt_root)
                return -EINVAL;
 
@@ -1669,9 +1655,7 @@ static int do_loopback(struct path *path, const char *old_name,
        LIST_HEAD(umount_list);
        struct path old_path;
        struct mount *mnt = NULL, *old;
-       int err = mount_is_safe(path);
-       if (err)
-               return err;
+       int err;
        if (!old_name || !*old_name)
                return -EINVAL;
        err = kern_path(old_name, LOOKUP_FOLLOW|LOOKUP_AUTOMOUNT, &old_path);
@@ -1748,9 +1732,6 @@ static int do_remount(struct path *path, int flags, int mnt_flags,
        struct super_block *sb = path->mnt->mnt_sb;
        struct mount *mnt = real_mount(path->mnt);
 
-       if (!capable(CAP_SYS_ADMIN))
-               return -EPERM;
-
        if (!check_mnt(mnt))
                return -EINVAL;
 
@@ -1764,6 +1745,8 @@ static int do_remount(struct path *path, int flags, int mnt_flags,
        down_write(&sb->s_umount);
        if (flags & MS_BIND)
                err = change_mount_flags(path->mnt, flags);
+       else if (!capable(CAP_SYS_ADMIN))
+               err = -EPERM;
        else
                err = do_remount_sb(sb, flags, data, 0);
        if (!err) {
@@ -1796,9 +1779,7 @@ static int do_move_mount(struct path *path, const char *old_name)
        struct path old_path, parent_path;
        struct mount *p;
        struct mount *old;
-       int err = 0;
-       if (!ns_capable(real_mount(path->mnt)->mnt_ns->user_ns, CAP_SYS_ADMIN))
-               return -EPERM;
+       int err;
        if (!old_name || !*old_name)
                return -EINVAL;
        err = kern_path(old_name, LOOKUP_FOLLOW, &old_path);
@@ -1933,18 +1914,13 @@ static int do_new_mount(struct path *path, const char *fstype, int flags,
                        int mnt_flags, const char *name, void *data)
 {
        struct file_system_type *type;
-       struct user_namespace *user_ns;
+       struct user_namespace *user_ns = current->nsproxy->mnt_ns->user_ns;
        struct vfsmount *mnt;
        int err;
 
        if (!fstype)
                return -EINVAL;
 
-       /* we need capabilities... */
-       user_ns = real_mount(path->mnt)->mnt_ns->user_ns;
-       if (!ns_capable(user_ns, CAP_SYS_ADMIN))
-               return -EPERM;
-
        type = get_fs_type(fstype);
        if (!type)
                return -ENODEV;
@@ -2258,6 +2234,9 @@ long do_mount(const char *dev_name, const char *dir_name,
        if (retval)
                goto dput_out;
 
+       if (!may_mount())
+               return -EPERM;
+
        /* Default to relatime unless overriden */
        if (!(flags & MS_NOATIME))
                mnt_flags |= MNT_RELATIME;
@@ -2567,7 +2546,7 @@ SYSCALL_DEFINE2(pivot_root, const char __user *, new_root,
        struct mount *new_mnt, *root_mnt;
        int error;
 
-       if (!ns_capable(current->nsproxy->mnt_ns->user_ns, CAP_SYS_ADMIN))
+       if (!may_mount())
                return -EPERM;
 
        error = user_path_dir(new_root, &new);