restore: don't check tcore->thread_core

It is always not NULL in sigreturn_restore().

CID 164716 (#1 of 1): Dereference after null check (FORWARD_NULL)
64. var_deref_model: Passing tcore to construct_sigframe, which dereferences null tcore->thread_core. [show details]
Signed-off-by: Andrew Vagin <avagin@virtuozzo.com>
Acked-by: Cyrill Gorcunov <gorcunov@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@virtuozzo.com>

criu/cr-restore.c

@@ -2918,21 +2918,19 @@ static int sigreturn_restore(pid_t pid, struct task_restore_args *task_args, uns
 
 		rst_reloc_creds(&thread_args[i], &creds_pos_next);
 
-		if (tcore->thread_core) {
-			thread_args[i].has_futex	= true;
-			thread_args[i].futex_rla	= tcore->thread_core->futex_rla;
-			thread_args[i].futex_rla_len	= tcore->thread_core->futex_rla_len;
-			thread_args[i].pdeath_sig	= tcore->thread_core->pdeath_sig;
-			if (tcore->thread_core->pdeath_sig > _KNSIG) {
-				pr_err("Pdeath signal is too big\n");
-				goto err;
-			}
-
-			ret = prep_sched_info(&thread_args[i].sp, tcore->thread_core);
-			if (ret)
-				goto err;
+		thread_args[i].has_futex	= true;
+		thread_args[i].futex_rla	= tcore->thread_core->futex_rla;
+		thread_args[i].futex_rla_len	= tcore->thread_core->futex_rla_len;
+		thread_args[i].pdeath_sig	= tcore->thread_core->pdeath_sig;
+		if (tcore->thread_core->pdeath_sig > _KNSIG) {
+			pr_err("Pdeath signal is too big\n");
+			goto err;
 		}
 
+		ret = prep_sched_info(&thread_args[i].sp, tcore->thread_core);
+		if (ret)
+			goto err;
+
 		thread_args[i].mz = mz + i;
 		sigframe = (struct rt_sigframe *)&mz[i].rt_sigframe;