commit 723eb80e24b3b44ecccf086452fcd064e425b348
author Thomas Gleixner <tglx@linutronix.de> Wed Feb 03 13:45:38 2021 +0000
committer Todd Kjos <tkjos@google.com> Thu May 27 17:02:19 2021 -0700
tree 62a59001560a13a86af3406dbecf9921e1be4c7a
parent 4958764d0ab729c7f288cf6a615313421a97c0b6

futex: Simplify fixup_pi_state_owner()

[ Upstream commit f2dac39d93987f7de1e20b3988c8685523247ae2 ]

Too many gotos already and an upcoming fix would make it even more
unreadable.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: stable@vger.kernel.org
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

kernel/futex.c

diff --git a/kernel/futex.c b/kernel/futex.c
index c098214..49d7c97 100644
--- a/kernel/futex.c
+++ b/kernel/futex.c
@@ -2148,18 +2148,16 @@
 	spin_unlock(q->lock_ptr);
 }
 
-static int fixup_pi_state_owner(u32 __user *uaddr, struct futex_q *q,
-				struct task_struct *argowner)
+static int __fixup_pi_state_owner(u32 __user *uaddr, struct futex_q *q,
+				  struct task_struct *argowner)
 {
 	struct futex_pi_state *pi_state = q->pi_state;
-	u32 uval, uninitialized_var(curval), newval;
 	struct task_struct *oldowner, *newowner;
-	u32 newtid;
-	int ret;
-
-	lockdep_assert_held(q->lock_ptr);
+	u32 uval, curval, newval, newtid;
+	int err = 0;
 
 	oldowner = pi_state->owner;
+
 	/* Owner died? */
 	if (!pi_state->owner)
 		newtid |= FUTEX_OWNER_DIED;
@@ -2200,7 +2198,7 @@
 
 		if (__rt_mutex_futex_trylock(&pi_state->pi_mutex)) {
 			/* We got the lock after all, nothing to fix. */
-			return 0;
+			return 1;
 		}
 
 		/*
@@ -2215,7 +2213,7 @@
 			 * We raced against a concurrent self; things are
 			 * already fixed up. Nothing to do.
 			 */
-			return 0;
+			return 1;
 		}
 		newowner = argowner;
 	}
@@ -2256,7 +2254,7 @@
 handle_fault:
 	spin_unlock(q->lock_ptr);
 
-	ret = fault_in_user_writeable(uaddr);
+	err = fault_in_user_writeable(uaddr);
 
 	spin_lock(q->lock_ptr);
 
@@ -2264,12 +2262,27 @@
 	 * Check if someone else fixed it for us:
 	 */
 	if (pi_state->owner != oldowner)
-		return 0;
+		return argowner == current;
 
-	if (ret)
-		return ret;
+	/* Retry if err was -EAGAIN or the fault in succeeded */
+	if (!err)
+		goto retry;
 
-	goto retry;
+	return err;
+}
+
+static int fixup_pi_state_owner(u32 __user *uaddr, struct futex_q *q,
+				struct task_struct *argowner)
+{
+	struct futex_pi_state *pi_state = q->pi_state;
+	int ret;
+
+	lockdep_assert_held(q->lock_ptr);
+
+	raw_spin_lock_irq(&pi_state->pi_mutex.wait_lock);
+	ret = __fixup_pi_state_owner(uaddr, q, argowner);
+	raw_spin_unlock_irq(&pi_state->pi_mutex.wait_lock);
+	return ret;
 }
 
 static long futex_wait_restart(struct restart_block *restart);