ring-buffer: Clear pages on error in ring_buffer_subbuf_order_set() failure

On failure to allocate ring buffer pages, the pointer to the CPU buffer
pages is freed, but the pages that were allocated previously were not.
Make sure they are freed too.

Link: https://lore.kernel.org/linux-trace-kernel/20231219185629.179352802@goodmis.org

Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Tzvetomir Stoyanov <tz.stoyanov@gmail.com>
Cc: Vincent Donnefort <vdonnefort@google.com>
Cc: Kent Overstreet <kent.overstreet@gmail.com>
Fixes: f9b94daa ("tracing: Set new size of the ring buffer sub page")
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>

kernel/trace/ring_buffer.c

@@ -5927,6 +5927,7 @@ int ring_buffer_subbuf_order_set(struct trace_buffer *buffer, int order)
 	for_each_buffer_cpu(buffer, cpu) {
 		if (!cpu_buffers[cpu])
 			continue;
+		rb_free_cpu_buffer(cpu_buffers[cpu]);
 		kfree(cpu_buffers[cpu]);
 	}
 	kfree(cpu_buffers);