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-rw-r--r--fs/namespace.c37
1 files changed, 25 insertions, 12 deletions
diff --git a/fs/namespace.c b/fs/namespace.c
index 64627f883bf2..877e4277f496 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -2867,25 +2867,38 @@ bool current_chrooted(void)
return chrooted;
}
-void update_mnt_policy(struct user_namespace *userns)
+bool fs_fully_visible(struct file_system_type *type)
{
struct mnt_namespace *ns = current->nsproxy->mnt_ns;
struct mount *mnt;
+ bool visible = false;
- down_read(&namespace_sem);
+ if (unlikely(!ns))
+ return false;
+
+ namespace_lock();
list_for_each_entry(mnt, &ns->list, mnt_list) {
- switch (mnt->mnt.mnt_sb->s_magic) {
- case SYSFS_MAGIC:
- userns->may_mount_sysfs = true;
- break;
- case PROC_SUPER_MAGIC:
- userns->may_mount_proc = true;
- break;
+ struct mount *child;
+ if (mnt->mnt.mnt_sb->s_type != type)
+ continue;
+
+ /* This mount is not fully visible if there are any child mounts
+ * that cover anything except for empty directories.
+ */
+ list_for_each_entry(child, &mnt->mnt_mounts, mnt_child) {
+ struct inode *inode = child->mnt_mountpoint->d_inode;
+ if (!S_ISDIR(inode->i_mode))
+ goto next;
+ if (inode->i_nlink != 2)
+ goto next;
}
- if (userns->may_mount_sysfs && userns->may_mount_proc)
- break;
+ visible = true;
+ goto found;
+ next: ;
}
- up_read(&namespace_sem);
+found:
+ namespace_unlock();
+ return visible;
}
static void *mntns_get(struct task_struct *task)