Merge tag 'trace-v7.3-2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-tracegrafted

Pull tracing fixes from Steven Rostedt:

 - Fix error output of boot instance creation failure

   Currently if a boot instance creation fails, instead of printing out
   the name of the instance that failed, it prints "(null)". That is
   because it prints "cur_str" that had already been processed by
   strsep(). Print the saved name instead.

   While at it, print the error code of the failure.

 - Fix use-after-free for same named historgrams

   Histograms can be named so that they can be used in multiple events.
   But if the named histogram has a variable attached, the second event
   that uses the named histogram which duplicates it and needs to free
   the original after duplication leaves the old variable in place and
   still visible. If another histogram uses than variable, it will use
   the stale one which will try to reference the freed duplicate
   histogram and crash the kernel.

   Free the duplicate variables along with the duplicated histogram
   data.

 - Check return value of kthread_run() in event self test

   The events self tests uses a kthread for testing but does not check
   if it succeeded in creating a kthread. If the kthread creation were
   to fail, the code will still try to call kthread_stop() on the error
   returned.

 - Fix race between reading trace_pipe and updating subbuffer size

   If a user is reading the trace_pipe file at the same time they update
   the ring buffer sub-buffer size, can cause the trace_pipe read to
   read stale data. Add trace_access_lock() around updating the ring
   buffer sub-buffer size.

 - Fix eventfs_inode on failure path in creation of the events directory

   In the creation of the "events" directory, if after allocating the
   eventfs_inode a failure is detected, it calls cleanup_ei() which
   calls free_ei(). The free_ei() will test if eventfs_inode being freed
   has no children. It is a bug if it does. But on the failure case of
   the creation of the "events" directory, the children lists have not
   yet been initialized and the free will trigger a warning because
   list_empty() on an uninitialized list returns false.

   Move the initialization into init_ei() where it makes more sense and
   makes sure that a created eventfs_inode has its lists initialized
   upon creation.

 - Check return value of kthread_run() in ftrace direct sample code

   The sample code that shows how to use the ftrace direct calls does
   not test the return of kthread_run() to see if it succeeds. Return a
   failure if the kthread_run() doesn't succeed.

 - Clear user events state on fork in case of alloc failure

   On fork, the child gets a pointer to the parent's user events state.
   It makes a copy of it then updates the child's pointer to it. But if
   the allocation fails, the duplication function leaves the child with
   a pointer to its parent's descriptor. When the child cleans up its
   data, it will free the parent's descriptor while the parent is still
   using it.

   In the duplication function, set the child's user_event_mm to NULL
   before testing if the allocation succeeded, and when it exits it will
   not free the parent's descriptor.

 - Fix retry exhaustion in simple ring buffer reader swap

   simple_ring_buffer_swap_reader_page() starts with retry set to 8 and
   post-decrements it only after a failed link replacement. On the final
   attempt, a successful replacement leaves retry at zero, while a
   failed replacement leaves it at -1.

   But the check for success expects the retry value to be non-zero and
   exits with an error on zero. This is the opposite result. Fix it.

 - Fail nicely when the remote swap_reader_page() returns an error

   Currently, if the swap_reader_page() of a remote buffer fails, it
   triggers a WARN_ON_ONCE() and continues normally. Instead, have it
   exit with an error and a pr_warn() print instead of a full WARNING.

* tag 'trace-v7.3-2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace:
  ring-buffer: Stop remote reader update when page swap fails
  tracing: Fix retry exhaustion in simple ring buffer reader swap
  tracing/user_events: Clear copied tracing state before fork duplication
  samples/ftrace: Fix kthread_stop() on ERR_PTR in ftrace-direct-multi-modify
  samples/ftrace: Fix kthread_stop() on ERR_PTR in ftrace-direct-modify
  eventfs: Initialize ei->children and ei->list in init_ei()
  tracing: Fix use-after-free in trace_pipe read on sub-buffer order change
  tracing: Fix crash passing ERR_PTR to kthread_stop()
  tracing: Fix use-after-free with same-name named triggers
  tracing: Fix logged instance name on creation failure

1 files changed, 407 insertions, 0 deletions

diff --git a/lib/klist.c b/lib/klist.c
new file mode 100644
index 000000000..332a4fbf1
--- /dev/null
+++ b/lib/klist.c
@@ -0,0 +1,407 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * klist.c - Routines for manipulating klists.
+ *
+ * Copyright (C) 2005 Patrick Mochel
+ *
+ * This klist interface provides a couple of structures that wrap around
+ * struct list_head to provide explicit list "head" (struct klist) and list
+ * "node" (struct klist_node) objects. For struct klist, a spinlock is
+ * included that protects access to the actual list itself. struct
+ * klist_node provides a pointer to the klist that owns it and a kref
+ * reference count that indicates the number of current users of that node
+ * in the list.
+ *
+ * The entire point is to provide an interface for iterating over a list
+ * that is safe and allows for modification of the list during the
+ * iteration (e.g. insertion and removal), including modification of the
+ * current node on the list.
+ *
+ * It works using a 3rd object type - struct klist_iter - that is declared
+ * and initialized before an iteration. klist_next() is used to acquire the
+ * next element in the list. It returns NULL if there are no more items.
+ * Internally, that routine takes the klist's lock, decrements the
+ * reference count of the previous klist_node and increments the count of
+ * the next klist_node. It then drops the lock and returns.
+ *
+ * There are primitives for adding and removing nodes to/from a klist.
+ * When deleting, klist_del() will simply decrement the reference count.
+ * Only when the count goes to 0 is the node removed from the list.
+ * klist_remove() will try to delete the node from the list and block until
+ * it is actually removed. This is useful for objects (like devices) that
+ * have been removed from the system and must be freed (but must wait until
+ * all accessors have finished).
+ */
+
+#include <linux/klist.h>
+#include <linux/export.h>
+#include <linux/sched.h>
+
+/*
+ * Use the lowest bit of n_klist to mark deleted nodes and exclude
+ * dead ones from iteration.
+ */
+#define KNODE_DEAD		1LU
+#define KNODE_KLIST_MASK	~KNODE_DEAD
+
+static struct klist *knode_klist(struct klist_node *knode)
+{
+	return (struct klist *)
+		((unsigned long)knode->n_klist & KNODE_KLIST_MASK);
+}
+
+static bool knode_dead(struct klist_node *knode)
+{
+	return (unsigned long)knode->n_klist & KNODE_DEAD;
+}
+
+static void knode_set_klist(struct klist_node *knode, struct klist *klist)
+{
+	knode->n_klist = klist;
+	/* no knode deserves to start its life dead */
+	WARN_ON(knode_dead(knode));
+}
+
+static void knode_kill(struct klist_node *knode)
+{
+	/* and no knode should die twice ever either, see we're very humane */
+	WARN_ON(knode_dead(knode));
+	*(unsigned long *)&knode->n_klist |= KNODE_DEAD;
+}
+
+/**
+ * klist_init - Initialize a klist structure.
+ * @k: The klist we're initializing.
+ * @get: The get function for the embedding object (NULL if none)
+ * @put: The put function for the embedding object (NULL if none)
+ *
+ * Initialises the klist structure.  If the klist_node structures are
+ * going to be embedded in refcounted objects (necessary for safe
+ * deletion) then the get/put arguments are used to initialise
+ * functions that take and release references on the embedding
+ * objects.
+ */
+void klist_init(struct klist *k, void (*get)(struct klist_node *),
+		void (*put)(struct klist_node *))
+{
+	INIT_LIST_HEAD(&k->k_list);
+	spin_lock_init(&k->k_lock);
+	k->get = get;
+	k->put = put;
+}
+EXPORT_SYMBOL_GPL(klist_init);
+
+static void add_head(struct klist *k, struct klist_node *n)
+{
+	spin_lock(&k->k_lock);
+	list_add(&n->n_node, &k->k_list);
+	spin_unlock(&k->k_lock);
+}
+
+static void add_tail(struct klist *k, struct klist_node *n)
+{
+	spin_lock(&k->k_lock);
+	list_add_tail(&n->n_node, &k->k_list);
+	spin_unlock(&k->k_lock);
+}
+
+static void klist_node_init(struct klist *k, struct klist_node *n)
+{
+	INIT_LIST_HEAD(&n->n_node);
+	kref_init(&n->n_ref);
+	knode_set_klist(n, k);
+	if (k->get)
+		k->get(n);
+}
+
+/**
+ * klist_add_head - Initialize a klist_node and add it to front.
+ * @n: node we're adding.
+ * @k: klist it's going on.
+ */
+void klist_add_head(struct klist_node *n, struct klist *k)
+{
+	klist_node_init(k, n);
+	add_head(k, n);
+}
+EXPORT_SYMBOL_GPL(klist_add_head);
+
+/**
+ * klist_add_tail - Initialize a klist_node and add it to back.
+ * @n: node we're adding.
+ * @k: klist it's going on.
+ */
+void klist_add_tail(struct klist_node *n, struct klist *k)
+{
+	klist_node_init(k, n);
+	add_tail(k, n);
+}
+EXPORT_SYMBOL_GPL(klist_add_tail);
+
+/**
+ * klist_add_behind - Init a klist_node and add it after an existing node
+ * @n: node we're adding.
+ * @pos: node to put @n after
+ */
+void klist_add_behind(struct klist_node *n, struct klist_node *pos)
+{
+	struct klist *k = knode_klist(pos);
+
+	klist_node_init(k, n);
+	spin_lock(&k->k_lock);
+	list_add(&n->n_node, &pos->n_node);
+	spin_unlock(&k->k_lock);
+}
+EXPORT_SYMBOL_GPL(klist_add_behind);
+
+/**
+ * klist_add_before - Init a klist_node and add it before an existing node
+ * @n: node we're adding.
+ * @pos: node to put @n after
+ */
+void klist_add_before(struct klist_node *n, struct klist_node *pos)
+{
+	struct klist *k = knode_klist(pos);
+
+	klist_node_init(k, n);
+	spin_lock(&k->k_lock);
+	list_add_tail(&n->n_node, &pos->n_node);
+	spin_unlock(&k->k_lock);
+}
+EXPORT_SYMBOL_GPL(klist_add_before);
+
+struct klist_waiter {
+	struct list_head list;
+	struct klist_node *node;
+	struct task_struct *process;
+	int woken;
+};
+
+static DEFINE_SPINLOCK(klist_remove_lock);
+static LIST_HEAD(klist_remove_waiters);
+
+static void klist_release(struct kref *kref)
+{
+	struct klist_waiter *waiter, *tmp;
+	struct klist_node *n = container_of(kref, struct klist_node, n_ref);
+
+	WARN_ON(!knode_dead(n));
+	list_del(&n->n_node);
+	spin_lock(&klist_remove_lock);
+	list_for_each_entry_safe(waiter, tmp, &klist_remove_waiters, list) {
+		if (waiter->node != n)
+			continue;
+
+		list_del(&waiter->list);
+		waiter->woken = 1;
+		mb();
+		wake_up_process(waiter->process);
+	}
+	spin_unlock(&klist_remove_lock);
+	knode_set_klist(n, NULL);
+}
+
+static int klist_dec_and_del(struct klist_node *n)
+{
+	return kref_put(&n->n_ref, klist_release);
+}
+
+static void klist_put(struct klist_node *n, bool kill)
+{
+	struct klist *k = knode_klist(n);
+	void (*put)(struct klist_node *) = k->put;
+
+	spin_lock(&k->k_lock);
+	if (kill)
+		knode_kill(n);
+	if (!klist_dec_and_del(n))
+		put = NULL;
+	spin_unlock(&k->k_lock);
+	if (put)
+		put(n);
+}
+
+/**
+ * klist_del - Decrement the reference count of node and try to remove.
+ * @n: node we're deleting.
+ */
+void klist_del(struct klist_node *n)
+{
+	klist_put(n, true);
+}
+EXPORT_SYMBOL_GPL(klist_del);
+
+/**
+ * klist_remove - Decrement the refcount of node and wait for it to go away.
+ * @n: node we're removing.
+ */
+void klist_remove(struct klist_node *n)
+{
+	struct klist_waiter waiter;
+
+	waiter.node = n;
+	waiter.process = current;
+	waiter.woken = 0;
+	spin_lock(&klist_remove_lock);
+	list_add(&waiter.list, &klist_remove_waiters);
+	spin_unlock(&klist_remove_lock);
+
+	klist_del(n);
+
+	for (;;) {
+		set_current_state(TASK_UNINTERRUPTIBLE);
+		if (waiter.woken)
+			break;
+		schedule();
+	}
+	__set_current_state(TASK_RUNNING);
+}
+EXPORT_SYMBOL_GPL(klist_remove);
+
+/**
+ * klist_node_attached - Say whether a node is bound to a list or not.
+ * @n: Node that we're testing.
+ */
+int klist_node_attached(struct klist_node *n)
+{
+	return (n->n_klist != NULL);
+}
+EXPORT_SYMBOL_GPL(klist_node_attached);
+
+/**
+ * klist_iter_init_node - Initialize a klist_iter structure.
+ * @k: klist we're iterating.
+ * @i: klist_iter we're filling.
+ * @n: node to start with.
+ *
+ * Similar to klist_iter_init(), but starts the action off with @n,
+ * instead of with the list head.
+ */
+void klist_iter_init_node(struct klist *k, struct klist_iter *i,
+			  struct klist_node *n)
+{
+	i->i_klist = k;
+	i->i_cur = NULL;
+	if (n && kref_get_unless_zero(&n->n_ref))
+		i->i_cur = n;
+}
+EXPORT_SYMBOL_GPL(klist_iter_init_node);
+
+/**
+ * klist_iter_init - Iniitalize a klist_iter structure.
+ * @k: klist we're iterating.
+ * @i: klist_iter structure we're filling.
+ *
+ * Similar to klist_iter_init_node(), but start with the list head.
+ */
+void klist_iter_init(struct klist *k, struct klist_iter *i)
+{
+	klist_iter_init_node(k, i, NULL);
+}
+EXPORT_SYMBOL_GPL(klist_iter_init);
+
+/**
+ * klist_iter_exit - Finish a list iteration.
+ * @i: Iterator structure.
+ *
+ * Must be called when done iterating over list, as it decrements the
+ * refcount of the current node. Necessary in case iteration exited before
+ * the end of the list was reached, and always good form.
+ */
+void klist_iter_exit(struct klist_iter *i)
+{
+	if (i->i_cur) {
+		klist_put(i->i_cur, false);
+		i->i_cur = NULL;
+	}
+}
+EXPORT_SYMBOL_GPL(klist_iter_exit);
+
+static struct klist_node *to_klist_node(struct list_head *n)
+{
+	return container_of(n, struct klist_node, n_node);
+}
+
+/**
+ * klist_prev - Ante up prev node in list.
+ * @i: Iterator structure.
+ *
+ * First grab list lock. Decrement the reference count of the previous
+ * node, if there was one. Grab the prev node, increment its reference
+ * count, drop the lock, and return that prev node.
+ */
+struct klist_node *klist_prev(struct klist_iter *i)
+{
+	void (*put)(struct klist_node *) = i->i_klist->put;
+	struct klist_node *last = i->i_cur;
+	struct klist_node *prev;
+	unsigned long flags;
+
+	spin_lock_irqsave(&i->i_klist->k_lock, flags);
+
+	if (last) {
+		prev = to_klist_node(last->n_node.prev);
+		if (!klist_dec_and_del(last))
+			put = NULL;
+	} else
+		prev = to_klist_node(i->i_klist->k_list.prev);
+
+	i->i_cur = NULL;
+	while (prev != to_klist_node(&i->i_klist->k_list)) {
+		if (likely(!knode_dead(prev))) {
+			kref_get(&prev->n_ref);
+			i->i_cur = prev;
+			break;
+		}
+		prev = to_klist_node(prev->n_node.prev);
+	}
+
+	spin_unlock_irqrestore(&i->i_klist->k_lock, flags);
+
+	if (put && last)
+		put(last);
+	return i->i_cur;
+}
+EXPORT_SYMBOL_GPL(klist_prev);
+
+/**
+ * klist_next - Ante up next node in list.
+ * @i: Iterator structure.
+ *
+ * First grab list lock. Decrement the reference count of the previous
+ * node, if there was one. Grab the next node, increment its reference
+ * count, drop the lock, and return that next node.
+ */
+struct klist_node *klist_next(struct klist_iter *i)
+{
+	void (*put)(struct klist_node *) = i->i_klist->put;
+	struct klist_node *last = i->i_cur;
+	struct klist_node *next;
+	unsigned long flags;
+
+	spin_lock_irqsave(&i->i_klist->k_lock, flags);
+
+	if (last) {
+		next = to_klist_node(last->n_node.next);
+		if (!klist_dec_and_del(last))
+			put = NULL;
+	} else
+		next = to_klist_node(i->i_klist->k_list.next);
+
+	i->i_cur = NULL;
+	while (next != to_klist_node(&i->i_klist->k_list)) {
+		if (likely(!knode_dead(next))) {
+			kref_get(&next->n_ref);
+			i->i_cur = next;
+			break;
+		}
+		next = to_klist_node(next->n_node.next);
+	}
+
+	spin_unlock_irqrestore(&i->i_klist->k_lock, flags);
+
+	if (put && last)
+		put(last);
+	return i->i_cur;
+}
+EXPORT_SYMBOL_GPL(klist_next);