tracing: Fix missing trace_boot_init_histograms kstrdup NULL checks

trace_boot_init_histograms misses NULL pointer checks for kstrdup
failure.

Link: https://lkml.kernel.org/r/20211015195550.22742-1-mathieu.desnoyers@efficios.com

Fixes: 64dc7f69 ("tracing/boot: Show correct histogram error command")
Acked-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

kernel/trace/trace_boot.c

@@ -430,6 +430,8 @@ trace_boot_init_histograms(struct trace_event_file *file,
 		/* All digit started node should be instances. */
 		if (trace_boot_compose_hist_cmd(node, buf, size) == 0) {
 			tmp = kstrdup(buf, GFP_KERNEL);
+			if (!tmp)
+				return;
 			if (trigger_process_regex(file, buf) < 0)
 				pr_err("Failed to apply hist trigger: %s\n", tmp);
 			kfree(tmp);
@@ -439,6 +441,8 @@ trace_boot_init_histograms(struct trace_event_file *file,
 	if (xbc_node_find_subkey(hnode, "keys")) {
 		if (trace_boot_compose_hist_cmd(hnode, buf, size) == 0) {
 			tmp = kstrdup(buf, GFP_KERNEL);
+			if (!tmp)
+				return;
 			if (trigger_process_regex(file, buf) < 0)
 				pr_err("Failed to apply hist trigger: %s\n", tmp);
 			kfree(tmp);