[PATCH 7.1 250/271] ring-buffer: Initialise reader page order in rb_allocate_cpu_buffer()

7.1-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Vincent Donnefort <[email protected]>

commit 6d014e44b68ddd43f71288d2a4dbb1a259869149 upstream.

In rb_allocate_cpu_buffer(), bpage->order was omitted, leaving it as 0.
This is an issue for a ring-buffer with subbufs bigger than PAGE_SIZE if
when freed: free_buffer_page() relies on this value. Align the value
with the actual allocation size (buffer::subbuf_order).

Cc: [email protected]
Fixes: f9b94daa542a ("ring-buffer: Set new size of the ring buffer sub page")
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Vincent Donnefort <[email protected]>
Signed-off-by: Steven Rostedt <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
---
 kernel/trace/ring_buffer.c |    1 +
 1 file changed, 1 insertion(+)

--- a/kernel/trace/ring_buffer.c
+++ b/kernel/trace/ring_buffer.c
@@ -2400,6 +2400,7 @@ rb_allocate_cpu_buffer(struct trace_buff
 	bpage = alloc_cpu_page(cpu);
 	if (!bpage)
 		return NULL;
+	bpage->order = cpu_buffer->buffer->subbuf_order;
 
 	rb_check_bpage(cpu_buffer, bpage);