Merge tag 'locking_urgent_for_v6.17_rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull locking fixes from Borislav Petkov:

 - Make sure sanity checks down in the mutex lock path happen on the
   correct type of task so that they don't trigger falsely

 - Use the write unsafe user access pairs when writing a futex value to
   prevent an error on PowerPC which does user read and write accesses
   differently

* tag 'locking_urgent_for_v6.17_rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  locking: Fix __clear_task_blocked_on() warning from __ww_mutex_wound() path
  futex: Use user_write_access_begin/_end() in futex_put_value()

2 files changed, 8 insertions, 4 deletions

diff --git a/kernel/futex/futex.h b/kernel/futex/futex.h
index c74eac572acd..2cd57096c38e 100644
--- a/kernel/futex/futex.h
+++ b/kernel/futex/futex.h
@@ -319,13 +319,13 @@ static __always_inline int futex_put_value(u32 val, u32 __user *to)
 {
 	if (can_do_masked_user_access())
 		to = masked_user_access_begin(to);
-	else if (!user_read_access_begin(to, sizeof(*to)))
+	else if (!user_write_access_begin(to, sizeof(*to)))
 		return -EFAULT;
 	unsafe_put_user(val, to, Efault);
-	user_read_access_end();
+	user_write_access_end();
 	return 0;
 Efault:
-	user_read_access_end();
+	user_write_access_end();
 	return -EFAULT;
 }
 
diff --git a/kernel/locking/ww_mutex.h b/kernel/locking/ww_mutex.h
index 086fd5487ca7..31a785afee6c 100644
--- a/kernel/locking/ww_mutex.h
+++ b/kernel/locking/ww_mutex.h
@@ -342,8 +342,12 @@ static bool __ww_mutex_wound(struct MUTEX *lock,
 			 * When waking up the task to wound, be sure to clear the
 			 * blocked_on pointer. Otherwise we can see circular
 			 * blocked_on relationships that can't resolve.
+			 *
+			 * NOTE: We pass NULL here instead of lock, because we
+			 * are waking the mutex owner, who may be currently
+			 * blocked on a different mutex.
 			 */
-			__clear_task_blocked_on(owner, lock);
+			__clear_task_blocked_on(owner, NULL);
 			wake_q_add(wake_q, owner);
 		}
 		return true;