From 7f62d40d9cb50fd146fe8ff071f98fa3c1855083 Mon Sep 17 00:00:00 2001
From: "Eric W. Biederman" <ebiederm@xmission.com>
Date: Wed, 9 Feb 2022 08:52:41 -0600
Subject: [PATCH] task_work: Introduce task_work_pending
Git-commit: 7f62d40d9cb50fd146fe8ff071f98fa3c1855083
Patch-mainline: v5.18-rc1
References: git-fixes

Wrap the test of task->task_works in a helper function to make
it clear what is being tested.

All of the other readers of task->task_work use READ_ONCE and this is
even necessary on current as other processes can update
task->task_work.  So for consistency I have added READ_ONCE into
task_work_pending.

Reviewed-by: Kees Cook <keescook@chromium.org>
Link: https://lkml.kernel.org/r/20220309162454.123006-7-ebiederm@xmission.com
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: Gabriel Krisman Bertazi <krisman@suse.de>
---
 fs/io_uring.c             |    6 +++---
 include/linux/task_work.h |    5 +++++
 include/linux/tracehook.h |    4 ++--
 kernel/signal.c           |    4 ++--
 kernel/task_work.c        |    2 +-
 5 files changed, 13 insertions(+), 8 deletions(-)

--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -2706,7 +2706,7 @@ static inline unsigned int io_sqring_ent
 
 static inline bool io_run_task_work(void)
 {
-	if (test_thread_flag(TIF_NOTIFY_SIGNAL) || current->task_works) {
+	if (test_thread_flag(TIF_NOTIFY_SIGNAL) || task_work_pending(current)) {
 		__set_current_state(TASK_RUNNING);
 		tracehook_notify_signal();
 		return true;
@@ -7874,7 +7874,7 @@ static int io_sq_thread(void *data)
 		}
 
 		prepare_to_wait(&sqd->wait, &wait, TASK_INTERRUPTIBLE);
-		if (!io_sqd_events_pending(sqd) && !current->task_works) {
+		if (!io_sqd_events_pending(sqd) && !task_work_pending(current)) {
 			bool needs_sched = true;
 
 			list_for_each_entry(ctx, &sqd->ctx_list, sqd_list) {
@@ -10813,7 +10813,7 @@ static __cold void __io_uring_show_fdinf
 
 		hlist_for_each_entry(req, list, hash_node)
 			seq_printf(m, "  op=%d, task_works=%d\n", req->opcode,
-					req->task->task_works != NULL);
+					task_work_pending(req->task));
 	}
 
 	seq_puts(m, "CqOverflowList:\n");
--- a/include/linux/task_work.h
+++ b/include/linux/task_work.h
@@ -19,6 +19,11 @@ enum task_work_notify_mode {
 	TWA_SIGNAL,
 };
 
+static inline bool task_work_pending(struct task_struct *task)
+{
+	return READ_ONCE(task->task_works);
+}
+
 int task_work_add(struct task_struct *task, struct callback_head *twork,
 			enum task_work_notify_mode mode);
 
--- a/include/linux/tracehook.h
+++ b/include/linux/tracehook.h
@@ -185,7 +185,7 @@ static inline void tracehook_notify_resu
 	 * hlist_add_head(task->task_works);
 	 */
 	smp_mb__after_atomic();
-	if (unlikely(current->task_works))
+	if (unlikely(task_work_pending(current)))
 		task_work_run();
 
 #ifdef CONFIG_KEYS_REQUEST_CACHE
@@ -208,7 +208,7 @@ static inline void tracehook_notify_sign
 {
 	clear_thread_flag(TIF_NOTIFY_SIGNAL);
 	smp_mb__after_atomic();
-	if (current->task_works)
+	if (task_work_pending(current))
 		task_work_run();
 }
 
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -2346,7 +2346,7 @@ static void ptrace_do_notify(int signr,
 void ptrace_notify(int exit_code)
 {
 	BUG_ON((exit_code & (0x7f | ~0xffff)) != SIGTRAP);
-	if (unlikely(current->task_works))
+	if (unlikely(task_work_pending(current)))
 		task_work_run();
 
 	spin_lock_irq(&current->sighand->siglock);
@@ -2626,7 +2626,7 @@ bool get_signal(struct ksignal *ksig)
 	struct signal_struct *signal = current->signal;
 	int signr;
 
-	if (unlikely(current->task_works))
+	if (unlikely(task_work_pending(current)))
 		task_work_run();
 
 	/*
--- a/kernel/task_work.c
+++ b/kernel/task_work.c
@@ -78,7 +78,7 @@ task_work_cancel_match(struct task_struc
 	struct callback_head *work;
 	unsigned long flags;
 
-	if (likely(!task->task_works))
+	if (likely(!task_work_pending(task)))
 		return NULL;
 	/*
 	 * If cmpxchg() fails we continue without updating pprev.