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@@ -0,0 +1,177 @@
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+#include <linux/module.h>
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+#include <linux/sched.h>
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+#include <linux/fs.h>
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+#include <linux/path.h>
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+#include <linux/slab.h>
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+#include <linux/fs_struct.h>
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+
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+/*
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+ * Replace the fs->{rootmnt,root} with {mnt,dentry}. Put the old values.
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+ * It can block.
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+ */
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+void set_fs_root(struct fs_struct *fs, struct path *path)
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+{
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+ struct path old_root;
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+
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+ write_lock(&fs->lock);
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+ old_root = fs->root;
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+ fs->root = *path;
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+ path_get(path);
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+ write_unlock(&fs->lock);
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+ if (old_root.dentry)
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+ path_put(&old_root);
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+}
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+
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+/*
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+ * Replace the fs->{pwdmnt,pwd} with {mnt,dentry}. Put the old values.
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+ * It can block.
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+ */
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+void set_fs_pwd(struct fs_struct *fs, struct path *path)
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+{
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+ struct path old_pwd;
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+
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+ write_lock(&fs->lock);
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+ old_pwd = fs->pwd;
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+ fs->pwd = *path;
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+ path_get(path);
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+ write_unlock(&fs->lock);
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+
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+ if (old_pwd.dentry)
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+ path_put(&old_pwd);
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+}
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+
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+void chroot_fs_refs(struct path *old_root, struct path *new_root)
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+{
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+ struct task_struct *g, *p;
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+ struct fs_struct *fs;
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+ int count = 0;
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+
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+ read_lock(&tasklist_lock);
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+ do_each_thread(g, p) {
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+ task_lock(p);
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+ fs = p->fs;
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+ if (fs) {
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+ write_lock(&fs->lock);
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+ if (fs->root.dentry == old_root->dentry
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+ && fs->root.mnt == old_root->mnt) {
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+ path_get(new_root);
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+ fs->root = *new_root;
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+ count++;
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+ }
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+ if (fs->pwd.dentry == old_root->dentry
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+ && fs->pwd.mnt == old_root->mnt) {
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+ path_get(new_root);
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+ fs->pwd = *new_root;
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+ count++;
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+ }
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+ write_unlock(&fs->lock);
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+ }
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+ task_unlock(p);
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+ } while_each_thread(g, p);
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+ read_unlock(&tasklist_lock);
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+ while (count--)
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+ path_put(old_root);
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+}
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+
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+void free_fs_struct(struct fs_struct *fs)
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+{
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+ path_put(&fs->root);
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+ path_put(&fs->pwd);
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+ kmem_cache_free(fs_cachep, fs);
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+}
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+
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+void exit_fs(struct task_struct *tsk)
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+{
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+ struct fs_struct *fs = tsk->fs;
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+
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+ if (fs) {
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+ int kill;
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+ task_lock(tsk);
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+ write_lock(&fs->lock);
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+ tsk->fs = NULL;
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+ kill = !--fs->users;
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+ write_unlock(&fs->lock);
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+ task_unlock(tsk);
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+ if (kill)
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+ free_fs_struct(fs);
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+ }
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+}
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+
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+struct fs_struct *copy_fs_struct(struct fs_struct *old)
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+{
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+ struct fs_struct *fs = kmem_cache_alloc(fs_cachep, GFP_KERNEL);
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+ /* We don't need to lock fs - think why ;-) */
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+ if (fs) {
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+ fs->users = 1;
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+ fs->in_exec = 0;
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+ rwlock_init(&fs->lock);
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+ fs->umask = old->umask;
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+ read_lock(&old->lock);
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+ fs->root = old->root;
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+ path_get(&old->root);
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+ fs->pwd = old->pwd;
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+ path_get(&old->pwd);
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+ read_unlock(&old->lock);
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+ }
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+ return fs;
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+}
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+
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+int unshare_fs_struct(void)
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+{
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+ struct fs_struct *fs = current->fs;
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+ struct fs_struct *new_fs = copy_fs_struct(fs);
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+ int kill;
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+
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+ if (!new_fs)
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+ return -ENOMEM;
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+
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+ task_lock(current);
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+ write_lock(&fs->lock);
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+ kill = !--fs->users;
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+ current->fs = new_fs;
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+ write_unlock(&fs->lock);
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+ task_unlock(current);
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+
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+ if (kill)
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+ free_fs_struct(fs);
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+
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+ return 0;
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+}
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+EXPORT_SYMBOL_GPL(unshare_fs_struct);
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+
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+int current_umask(void)
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+{
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+ return current->fs->umask;
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+}
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+EXPORT_SYMBOL(current_umask);
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+
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+/* to be mentioned only in INIT_TASK */
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+struct fs_struct init_fs = {
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+ .users = 1,
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+ .lock = __RW_LOCK_UNLOCKED(init_fs.lock),
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+ .umask = 0022,
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+};
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+
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+void daemonize_fs_struct(void)
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+{
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+ struct fs_struct *fs = current->fs;
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+
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+ if (fs) {
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+ int kill;
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+
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+ task_lock(current);
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+
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+ write_lock(&init_fs.lock);
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+ init_fs.users++;
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+ write_unlock(&init_fs.lock);
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+
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+ write_lock(&fs->lock);
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+ current->fs = &init_fs;
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+ kill = !--fs->users;
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+ write_unlock(&fs->lock);
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+
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+ task_unlock(current);
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+ if (kill)
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+ free_fs_struct(fs);
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+ }
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+}
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