Merge branch 'exec-update-lock-for-v5.11' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace

Pull exec-update-lock update from Eric Biederman:
 "The key point of this is to transform exec_update_mutex into a
  rw_semaphore so readers can be separated from writers.

  This makes it easier to understand what the holders of the lock are
  doing, and makes it harder to contend or deadlock on the lock.

  The real deadlock fix wound up in perf_event_open"

* 'exec-update-lock-for-v5.11' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace:
  exec: Transform exec_update_mutex into a rw_semaphore

1 files changed, 3 insertions, 3 deletions

diff --git a/kernel/fork.c b/kernel/fork.c
index 4f44d87b82ef..41906a52a764 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -1225,7 +1225,7 @@ struct mm_struct *mm_access(struct task_struct *task, unsigned int mode)
 	struct mm_struct *mm;
 	int err;
 
-	err =  mutex_lock_killable(&task->signal->exec_update_mutex);
+	err =  down_read_killable(&task->signal->exec_update_lock);
 	if (err)
 		return ERR_PTR(err);
 
@@ -1235,7 +1235,7 @@ struct mm_struct *mm_access(struct task_struct *task, unsigned int mode)
 		mmput(mm);
 		mm = ERR_PTR(-EACCES);
 	}
-	mutex_unlock(&task->signal->exec_update_mutex);
+	up_read(&task->signal->exec_update_lock);
 
 	return mm;
 }
@@ -1595,7 +1595,7 @@ static int copy_signal(unsigned long clone_flags, struct task_struct *tsk)
 	sig->oom_score_adj_min = current->signal->oom_score_adj_min;
 
 	mutex_init(&sig->cred_guard_mutex);
-	mutex_init(&sig->exec_update_mutex);
+	init_rwsem(&sig->exec_update_lock);
 
 	return 0;
 }