lists.openwall.net   lists  /  announce  owl-users  owl-dev  john-users  john-dev  passwdqc-users  yescrypt  popa3d-users  /  oss-security  kernel-hardening  musl  sabotage  tlsify  passwords  /  crypt-dev  xvendor  /  Bugtraq  Full-Disclosure  linux-kernel  linux-netdev  linux-ext4  linux-hardening  linux-cve-announce  PHC 
Open Source and information security mailing list archives
 
Hash Suite: Windows password security audit tool. GUI, reports in PDF.
[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <20231210040451.424991712@goodmis.org>
Date:   Sat, 09 Dec 2023 22:54:15 -0500
From:   Steven Rostedt <rostedt@...dmis.org>
To:     linux-kernel@...r.kernel.org, linux-trace-kernel@...r.kernel.org
Cc:     Masami Hiramatsu <mhiramat@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Tzvetomir Stoyanov <tz.stoyanov@...il.com>,
        Vincent Donnefort <vdonnefort@...gle.com>,
        Kent Overstreet <kent.overstreet@...il.com>
Subject: [PATCH 11/14] ring-buffer: Keep the same size when updating the order

From: "Steven Rostedt (Google)" <rostedt@...dmis.org>

The function ring_buffer_subbuf_order_set() just updated the sub-buffers
to the new size, but this also changes the size of the buffer in doing so.
As the size is determined by nr_pages * subbuf_size. If the subbuf_size is
increased without decreasing the nr_pages, this causes the total size of
the buffer to increase.

This broke the latency tracers as the snapshot needs to be the same size
as the main buffer. The size of the snapshot buffer is only expanded when
needed, and because the order is still the same, the size becomes out of
sync with the main buffer, as the main buffer increased in size without
the tracing system knowing.

Calculate the nr_pages to allocate with the new subbuf_size to be
buffer_size / new_subbuf_size.

Fixes: TBD ("ring-buffer: Set new size of the ring buffer sub page")
Signed-off-by: Steven Rostedt (Google) <rostedt@...dmis.org>
---
 kernel/trace/ring_buffer.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
index 9725aab1b5eb..4726deccd997 100644
--- a/kernel/trace/ring_buffer.c
+++ b/kernel/trace/ring_buffer.c
@@ -6030,7 +6030,10 @@ int ring_buffer_subbuf_order_set(struct trace_buffer *buffer, int order)
 		if (!cpumask_test_cpu(cpu, buffer->cpumask))
 			continue;
 
-		nr_pages = buffer->buffers[cpu]->nr_pages;
+		/* Update the number of pages to match the new size */
+		nr_pages = old_size * buffer->buffers[cpu]->nr_pages;
+		nr_pages = DIV_ROUND_UP(nr_pages, buffer->subbuf_size);
+
 		cpu_buffers[cpu] = rb_allocate_cpu_buffer(buffer, nr_pages, cpu);
 		if (!cpu_buffers[cpu]) {
 			err = -ENOMEM;
-- 
2.42.0


Powered by blists - more mailing lists

Powered by Openwall GNU/*/Linux Powered by OpenVZ