get_signal: don't initialize ksig->info if SIGNAL_GROUP_EXIT/group_exec_task

This initialization is incomplete and unnecessary, neither do_group_exit()
nor PF_USER_WORKER need ksig->info.

Link: https://lkml.kernel.org/r/20240226165653.GA20834@redhat.com
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Cc: Christian Brauner <brauner@kernel.org>
Cc: Eric W. Biederman <ebiederm@xmission.com>
Cc: Peter Collingbourne <pcc@google.com>
Cc: Wen Yang <wenyang.linux@foxmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Author: oleg-nesterov

kernel/signal.c

@@ -2727,12 +2727,15 @@ bool get_signal(struct ksignal *ksig)
 		/* Has this task already been marked for death? */
 		if ((signal->flags & SIGNAL_GROUP_EXIT) ||
 		     signal->group_exec_task) {
-			clear_siginfo(&ksig->info);
-			ksig->info.si_signo = signr = SIGKILL;
+			signr = SIGKILL;
 			sigdelset(&current->pending.signal, SIGKILL);
 			trace_signal_deliver(SIGKILL, SEND_SIG_NOINFO,
-				&sighand->action[SIGKILL - 1]);
+					     &sighand->action[SIGKILL-1]);
 			recalc_sigpending();
+			/*
+			 * implies do_group_exit() or return to PF_USER_WORKER,
+			 * no need to initialize ksig->info/etc.
+			 */
 			goto fatal;
 		}