From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-18.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_GIT autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 05FC5C433ED for ; Mon, 5 Apr 2021 08:59:35 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id C3460610E8 for ; Mon, 5 Apr 2021 08:59:34 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236979AbhDEI7j (ORCPT ); Mon, 5 Apr 2021 04:59:39 -0400 Received: from mail.kernel.org ([198.145.29.99]:39746 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236892AbhDEI7G (ORCPT ); Mon, 5 Apr 2021 04:59:06 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 3BA576124C; Mon, 5 Apr 2021 08:59:00 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1617613140; bh=//WmnFmVLtQXzU5dY6f0l/d9OHrpMFaut7xKQMS1aV0=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=X7RCeC0C7D4g7fA9Aj3DTr4ehhKCpcrl/J59/8KffjYNrMt944Lxq8xxFLx6hJYt9 KRwtAuheLQqVJj5fmOPvmeCGCAhg9zhdtJvzAUenQKGqD2s1A31vdR+4uFbnY+0gHs wW429FRw1IOv/o5BBx9W3qhU3pRwEvO6wr3Nyk38= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Vasily Gorbik , "Steven Rostedt (VMware)" Subject: [PATCH 4.14 27/52] tracing: Fix stack trace event size Date: Mon, 5 Apr 2021 10:53:53 +0200 Message-Id: <20210405085022.875654072@linuxfoundation.org> X-Mailer: git-send-email 2.31.1 In-Reply-To: <20210405085021.996963957@linuxfoundation.org> References: <20210405085021.996963957@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Steven Rostedt (VMware) commit 9deb193af69d3fd6dd8e47f292b67c805a787010 upstream. Commit cbc3b92ce037 fixed an issue to modify the macros of the stack trace event so that user space could parse it properly. Originally the stack trace format to user space showed that the called stack was a dynamic array. But it is not actually a dynamic array, in the way that other dynamic event arrays worked, and this broke user space parsing for it. The update was to make the array look to have 8 entries in it. Helper functions were added to make it parse it correctly, as the stack was dynamic, but was determined by the size of the event stored. Although this fixed user space on how it read the event, it changed the internal structure used for the stack trace event. It changed the array size from [0] to [8] (added 8 entries). This increased the size of the stack trace event by 8 words. The size reserved on the ring buffer was the size of the stack trace event plus the number of stack entries found in the stack trace. That commit caused the amount to be 8 more than what was needed because it did not expect the caller field to have any size. This produced 8 entries of garbage (and reading random data) from the stack trace event: -0 [002] d... 1976396.837549: => trace_event_raw_event_sched_switch => __traceiter_sched_switch => __schedule => schedule_idle => do_idle => cpu_startup_entry => secondary_startup_64_no_verify => 0xc8c5e150ffff93de => 0xffff93de => 0 => 0 => 0xc8c5e17800000000 => 0x1f30affff93de => 0x00000004 => 0x200000000 Instead, subtract the size of the caller field from the size of the event to make sure that only the amount needed to store the stack trace is reserved. Link: https://lore.kernel.org/lkml/your-ad-here.call-01617191565-ext-9692@work.hours/ Cc: stable@vger.kernel.org Fixes: cbc3b92ce037 ("tracing: Set kernel_stack's caller size properly") Reported-by: Vasily Gorbik Tested-by: Vasily Gorbik Acked-by: Vasily Gorbik Signed-off-by: Steven Rostedt (VMware) Signed-off-by: Greg Kroah-Hartman --- kernel/trace/trace.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -2631,7 +2631,8 @@ static void __ftrace_trace_stack(struct size *= sizeof(unsigned long); event = __trace_buffer_lock_reserve(buffer, TRACE_STACK, - sizeof(*entry) + size, flags, pc); + (sizeof(*entry) - sizeof(entry->caller)) + size, + flags, pc); if (!event) goto out; entry = ring_buffer_event_data(event);