Merge tag 'filelock-v5.6-1' of git://git.kernel.org/pub/scm/linux/ker…

…nel/git/jlayton/linux

Pull file locking fixes from Jeff Layton:
 "Just a couple of late-breaking patches for the file locking code. The
  second patch (from yangerkun) fixes a rather nasty looking potential
  use-after-free that should go to stable.

  The other patch could technically wait for 5.7, but it's fairly
  innocuous so I figured we might as well take it"

* tag 'filelock-v5.6-1' of git://git.kernel.org/pub/scm/linux/kernel/git/jlayton/linux:
  locks: fix a potential use-after-free problem when wakeup a waiter
  fcntl: Distribute switch variables for initialization

fs/fcntl.c

@@ -735,8 +735,9 @@ static void send_sigio_to_task(struct task_struct *p,
 		return;
 
 	switch (signum) {
-		kernel_siginfo_t si;
-		default:
+		default: {
+			kernel_siginfo_t si;
+
 			/* Queue a rt signal with the appropriate fd as its
 			   value.  We use SI_SIGIO as the source, not 
 			   SI_KERNEL, since kernel signals always get 
@@ -769,6 +770,7 @@ static void send_sigio_to_task(struct task_struct *p,
 			si.si_fd    = fd;
 			if (!do_send_sig_info(signum, &si, p, type))
 				break;
+		}
 		/* fall-through - fall back on the old plain SIGIO signal */
 		case 0:
 			do_send_sig_info(SIGIO, SEND_SIG_PRIV, p, type);

fs/locks.c

@@ -753,20 +753,6 @@ int locks_delete_block(struct file_lock *waiter)
 {
 	int status = -ENOENT;
 
-	/*
-	 * If fl_blocker is NULL, it won't be set again as this thread
-	 * "owns" the lock and is the only one that might try to claim
-	 * the lock.  So it is safe to test fl_blocker locklessly.
-	 * Also if fl_blocker is NULL, this waiter is not listed on
-	 * fl_blocked_requests for some lock, so no other request can
-	 * be added to the list of fl_blocked_requests for this
-	 * request.  So if fl_blocker is NULL, it is safe to
-	 * locklessly check if fl_blocked_requests is empty.  If both
-	 * of these checks succeed, there is no need to take the lock.
-	 */
-	if (waiter->fl_blocker == NULL &&
-	    list_empty(&waiter->fl_blocked_requests))
-		return status;
 	spin_lock(&blocked_lock_lock);
 	if (waiter->fl_blocker)
 		status = 0;