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, 368 insertions, 0 deletions

diff --git a/io_uring/waitid.c b/io_uring/waitid.c
new file mode 100644
index 000000000..2b7560174
--- /dev/null
+++ b/io_uring/waitid.c
@@ -0,0 +1,368 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Support for async notification of waitid
+ */
+#include <linux/kernel.h>
+#include <linux/errno.h>
+#include <linux/fs.h>
+#include <linux/file.h>
+#include <linux/compat.h>
+#include <linux/io_uring.h>
+
+#include <uapi/linux/io_uring.h>
+
+#include "io_uring.h"
+#include "cancel.h"
+#include "waitid.h"
+#include "../kernel/exit.h"
+
+static void io_waitid_cb(struct io_tw_req tw_req, io_tw_token_t tw);
+
+#define IO_WAITID_CANCEL_FLAG	BIT(31)
+#define IO_WAITID_REF_MASK	GENMASK(30, 0)
+
+struct io_waitid {
+	struct file *file;
+	int which;
+	pid_t upid;
+	int options;
+	atomic_t refs;
+	struct wait_queue_head *head;
+	struct siginfo __user *infop;
+	struct waitid_info info;
+};
+
+static void io_waitid_free(struct io_kiocb *req)
+{
+	struct io_waitid_async *iwa = req->async_data;
+
+	put_pid(iwa->wo.wo_pid);
+	io_req_async_data_free(req);
+}
+
+static bool io_waitid_compat_copy_si(struct io_waitid *iw, int signo)
+{
+	struct compat_siginfo __user *infop;
+	bool ret;
+
+	infop = (struct compat_siginfo __user *) iw->infop;
+
+	if (!user_write_access_begin(infop, sizeof(*infop)))
+		return false;
+
+	unsafe_put_user(signo, &infop->si_signo, Efault);
+	unsafe_put_user(0, &infop->si_errno, Efault);
+	unsafe_put_user(iw->info.cause, &infop->si_code, Efault);
+	unsafe_put_user(iw->info.pid, &infop->si_pid, Efault);
+	unsafe_put_user(iw->info.uid, &infop->si_uid, Efault);
+	unsafe_put_user(iw->info.status, &infop->si_status, Efault);
+	ret = true;
+done:
+	user_write_access_end();
+	return ret;
+Efault:
+	ret = false;
+	goto done;
+}
+
+static bool io_waitid_copy_si(struct io_kiocb *req, int signo)
+{
+	struct io_waitid *iw = io_kiocb_to_cmd(req, struct io_waitid);
+	bool ret;
+
+	if (!iw->infop)
+		return true;
+
+	if (io_is_compat(req->ctx))
+		return io_waitid_compat_copy_si(iw, signo);
+
+	if (!user_write_access_begin(iw->infop, sizeof(*iw->infop)))
+		return false;
+
+	unsafe_put_user(signo, &iw->infop->si_signo, Efault);
+	unsafe_put_user(0, &iw->infop->si_errno, Efault);
+	unsafe_put_user(iw->info.cause, &iw->infop->si_code, Efault);
+	unsafe_put_user(iw->info.pid, &iw->infop->si_pid, Efault);
+	unsafe_put_user(iw->info.uid, &iw->infop->si_uid, Efault);
+	unsafe_put_user(iw->info.status, &iw->infop->si_status, Efault);
+	ret = true;
+done:
+	user_write_access_end();
+	return ret;
+Efault:
+	ret = false;
+	goto done;
+}
+
+static int io_waitid_finish(struct io_kiocb *req, int ret)
+{
+	int signo = 0;
+
+	if (ret > 0) {
+		signo = SIGCHLD;
+		ret = 0;
+	}
+
+	if (!io_waitid_copy_si(req, signo))
+		ret = -EFAULT;
+	io_waitid_free(req);
+	return ret;
+}
+
+static void io_waitid_remove_wq(struct io_kiocb *req)
+{
+	struct io_waitid *iw = io_kiocb_to_cmd(req, struct io_waitid);
+	struct wait_queue_head *head;
+
+	head = smp_load_acquire(&iw->head);
+	if (head) {
+		struct io_waitid_async *iwa = req->async_data;
+
+		smp_store_release(&iw->head, NULL);
+		spin_lock_irq(&head->lock);
+		list_del_init(&iwa->wo.child_wait.entry);
+		spin_unlock_irq(&head->lock);
+	}
+}
+
+static void io_waitid_complete(struct io_kiocb *req, int ret, bool copy_si)
+{
+	struct io_waitid *iw = io_kiocb_to_cmd(req, struct io_waitid);
+
+	/* anyone completing better be holding a reference */
+	WARN_ON_ONCE(!(atomic_read(&iw->refs) & IO_WAITID_REF_MASK));
+
+	lockdep_assert_held(&req->ctx->uring_lock);
+
+	hlist_del_init(&req->hash_node);
+	io_waitid_remove_wq(req);
+
+	if (copy_si)
+		ret = io_waitid_finish(req, ret);
+	else
+		io_waitid_free(req);
+	if (ret < 0)
+		req_set_fail(req);
+	io_req_set_res(req, ret, 0);
+}
+
+static bool __io_waitid_cancel(struct io_kiocb *req, bool copy_si)
+{
+	struct io_waitid *iw = io_kiocb_to_cmd(req, struct io_waitid);
+
+	lockdep_assert_held(&req->ctx->uring_lock);
+
+	/*
+	 * Mark us canceled regardless of ownership. This will prevent a
+	 * potential retry from a spurious wakeup.
+	 */
+	atomic_or(IO_WAITID_CANCEL_FLAG, &iw->refs);
+
+	/* claim ownership */
+	if (atomic_fetch_inc(&iw->refs) & IO_WAITID_REF_MASK)
+		return false;
+
+	io_waitid_complete(req, -ECANCELED, copy_si);
+	io_req_queue_tw_complete(req, -ECANCELED);
+	return true;
+}
+
+static bool io_waitid_cancel_cb(struct io_kiocb *req)
+{
+	return __io_waitid_cancel(req, true);
+}
+
+static bool io_waitid_cancel_nocopy_cb(struct io_kiocb *req)
+{
+	return __io_waitid_cancel(req, false);
+}
+
+int io_waitid_cancel(struct io_ring_ctx *ctx, struct io_cancel_data *cd,
+		     unsigned int issue_flags)
+{
+	return io_cancel_remove(ctx, cd, issue_flags, &ctx->waitid_list, io_waitid_cancel_cb);
+}
+
+bool io_waitid_remove_all(struct io_ring_ctx *ctx, struct io_uring_task *tctx,
+			  bool cancel_all)
+{
+	return io_cancel_remove_all(ctx, tctx, &ctx->waitid_list, cancel_all,
+				       tctx ? io_waitid_cancel_cb : io_waitid_cancel_nocopy_cb);
+}
+
+static inline bool io_waitid_drop_issue_ref(struct io_kiocb *req)
+{
+	struct io_waitid *iw = io_kiocb_to_cmd(req, struct io_waitid);
+
+	if (!atomic_sub_return(1, &iw->refs))
+		return false;
+
+	io_waitid_remove_wq(req);
+
+	/*
+	 * Wakeup triggered, racing with us. It was prevented from
+	 * completing because of that, queue up the tw to do that.
+	 */
+	req->io_task_work.func = io_waitid_cb;
+	io_req_task_work_add(req);
+	return true;
+}
+
+static void io_waitid_cb(struct io_tw_req tw_req, io_tw_token_t tw)
+{
+	struct io_kiocb *req = tw_req.req;
+	struct io_waitid_async *iwa = req->async_data;
+	struct io_ring_ctx *ctx = req->ctx;
+	int ret;
+
+	io_tw_lock(ctx, tw);
+	if (unlikely(tw.cancel)) {
+		io_waitid_complete(req, -ECANCELED, false);
+		io_req_task_complete(tw_req, tw);
+		return;
+	}
+
+	ret = __do_wait(&iwa->wo);
+
+	/*
+	 * If we get -ERESTARTSYS here, we need to re-arm and check again
+	 * to ensure we get another callback. If the retry works, then we can
+	 * just remove ourselves from the waitqueue again and finish the
+	 * request.
+	 */
+	if (unlikely(ret == -ERESTARTSYS)) {
+		struct io_waitid *iw = io_kiocb_to_cmd(req, struct io_waitid);
+
+		/* Don't retry if cancel found it meanwhile */
+		ret = -ECANCELED;
+		if (!(atomic_read(&iw->refs) & IO_WAITID_CANCEL_FLAG)) {
+			iw->head = &current->signal->wait_chldexit;
+			add_wait_queue(iw->head, &iwa->wo.child_wait);
+			ret = __do_wait(&iwa->wo);
+			if (ret == -ERESTARTSYS) {
+				/* retry armed, drop our ref */
+				io_waitid_drop_issue_ref(req);
+				return;
+			}
+			/* fall through to complete, will kill waitqueue */
+		}
+	}
+
+	io_waitid_complete(req, ret, true);
+	io_req_task_complete(tw_req, tw);
+}
+
+static int io_waitid_wait(struct wait_queue_entry *wait, unsigned mode,
+			  int sync, void *key)
+{
+	struct wait_opts *wo = container_of(wait, struct wait_opts, child_wait);
+	struct io_waitid_async *iwa = container_of(wo, struct io_waitid_async, wo);
+	struct io_kiocb *req = iwa->req;
+	struct io_waitid *iw = io_kiocb_to_cmd(req, struct io_waitid);
+	struct task_struct *p = key;
+
+	if (!pid_child_should_wake(wo, p))
+		return 0;
+
+	list_del_init(&wait->entry);
+	smp_store_release(&iw->head, NULL);
+
+	/* cancel is in progress */
+	if (atomic_fetch_inc(&iw->refs) & IO_WAITID_REF_MASK)
+		return 1;
+
+	req->io_task_work.func = io_waitid_cb;
+	__io_req_task_work_add(req, IOU_F_TWQ_IN_WAKE);
+	return 1;
+}
+
+int io_waitid_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
+{
+	struct io_waitid *iw = io_kiocb_to_cmd(req, struct io_waitid);
+	struct io_waitid_async *iwa;
+
+	if (sqe->addr || sqe->buf_index || sqe->addr3 || sqe->waitid_flags)
+		return -EINVAL;
+
+	iwa = io_uring_alloc_async_data(NULL, req);
+	if (unlikely(!iwa))
+		return -ENOMEM;
+	iwa->req = req;
+
+	iw->which = READ_ONCE(sqe->len);
+	iw->upid = READ_ONCE(sqe->fd);
+	iw->options = READ_ONCE(sqe->file_index);
+	iw->head = NULL;
+	iw->infop = u64_to_user_ptr(READ_ONCE(sqe->addr2));
+	memset(&iw->info, 0, sizeof(iw->info));
+	return 0;
+}
+
+int io_waitid(struct io_kiocb *req, unsigned int issue_flags)
+{
+	struct io_waitid *iw = io_kiocb_to_cmd(req, struct io_waitid);
+	struct io_waitid_async *iwa = req->async_data;
+	struct io_ring_ctx *ctx = req->ctx;
+	int ret;
+
+	ret = kernel_waitid_prepare(&iwa->wo, iw->which, iw->upid, &iw->info,
+					iw->options, NULL);
+	if (ret)
+		goto done;
+
+	/*
+	 * Mark the request as busy upfront, in case we're racing with the
+	 * wakeup. If we are, then we'll notice when we drop this initial
+	 * reference again after arming.
+	 */
+	atomic_set(&iw->refs, 1);
+
+	/*
+	 * Cancel must hold the ctx lock, so there's no risk of cancelation
+	 * finding us until a) we remain on the list, and b) the lock is
+	 * dropped. We only need to worry about racing with the wakeup
+	 * callback.
+	 */
+	io_ring_submit_lock(ctx, issue_flags);
+
+	/*
+	 * iw->head is valid under the ring lock, and as long as the request
+	 * is on the waitid_list where cancelations may find it.
+	 */
+	iw->head = &current->signal->wait_chldexit;
+	hlist_add_head(&req->hash_node, &ctx->waitid_list);
+
+	init_waitqueue_func_entry(&iwa->wo.child_wait, io_waitid_wait);
+	iwa->wo.child_wait.private = req->tctx->task;
+	add_wait_queue(iw->head, &iwa->wo.child_wait);
+
+	ret = __do_wait(&iwa->wo);
+	if (ret == -ERESTARTSYS) {
+		/*
+		 * Nobody else grabbed a reference, it'll complete when we get
+		 * a waitqueue callback, or if someone cancels it.
+		 */
+		if (!io_waitid_drop_issue_ref(req)) {
+			io_ring_submit_unlock(ctx, issue_flags);
+			return IOU_ISSUE_SKIP_COMPLETE;
+		}
+
+		/*
+		 * Wakeup triggered, racing with us. It was prevented from
+		 * completing because of that, queue up the tw to do that.
+		 */
+		io_ring_submit_unlock(ctx, issue_flags);
+		return IOU_ISSUE_SKIP_COMPLETE;
+	}
+
+	hlist_del_init(&req->hash_node);
+	io_waitid_remove_wq(req);
+	ret = io_waitid_finish(req, ret);
+
+	io_ring_submit_unlock(ctx, issue_flags);
+done:
+	if (ret < 0)
+		req_set_fail(req);
+	io_req_set_res(req, ret, 0);
+	return IOU_COMPLETE;
+}