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=-11.6 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_2 autolearn=ham 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 DA879C433DF for ; Thu, 15 Oct 2020 13:54:39 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 867C02223F for ; Thu, 15 Oct 2020 13:54:39 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1602770079; bh=dYBHRuEaYycITXh0W7hcI6XJbIFBShads9fTbeIMlxM=; h=Subject:From:To:Cc:Date:In-Reply-To:References:List-ID:From; b=y7/vU373vZgyf3bUaIN0VwK4I2BDqxn6AttCo7cmwsl/JWg+VHCZAvoB+DjbyFvH7 rO3y+c6d+cLrGlbNbCdSxxXuxalKrxWW2nCJRK0HEAK4wJcNcH3LR4xTOfdFvW2Dcb jjo2QUzzp2EwAIWVZ0H/l+CdbDxC1/4g3qkMz3dk= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730277AbgJONyi (ORCPT ); Thu, 15 Oct 2020 09:54:38 -0400 Received: from mail.kernel.org ([198.145.29.99]:50672 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729647AbgJONyh (ORCPT ); Thu, 15 Oct 2020 09:54:37 -0400 Received: from tzanussi-mobl (c-73-209-127-30.hsd1.il.comcast.net [73.209.127.30]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 6332522248; Thu, 15 Oct 2020 13:54:36 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1602770076; bh=dYBHRuEaYycITXh0W7hcI6XJbIFBShads9fTbeIMlxM=; h=Subject:From:To:Cc:Date:In-Reply-To:References:From; b=wf8DoI/YS8lVDKP88vlA+OKLJyFItcq+OlG0ySsV7w4Xl5XOaT7/AMWU7ubqQa0mn g6QywlwfnKS/9C+kMlcO0psGEuTDQ+AvW/Py4pOKhY+OGGvKJN3CYSV0sj8ul3DMM0 vYbSDJSBD2CfplfWq/zDjAHoMjcqjpym4sccHekA= Message-ID: <53e8d16bd6da17d0c1759b0743ae44f104832ce4.camel@kernel.org> Subject: Re: [PATCH] tracing: Check return value of __create_val_fields() before using its result From: Tom Zanussi To: Steven Rostedt , LKML Cc: Masami Hiramatsu , Ingo Molnar Date: Thu, 15 Oct 2020 08:54:34 -0500 In-Reply-To: <20201013154852.3abd8702@gandalf.local.home> References: <20201013154852.3abd8702@gandalf.local.home> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.28.5-0ubuntu0.18.04.1 Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Steve, On Tue, 2020-10-13 at 15:48 -0400, Steven Rostedt wrote: > From: "Steven Rostedt (VMware)" > > After having a typo for writing a histogram trigger. > > Wrote: > echo 'hist:key=pid:ts=common_timestamp.usec' > > events/sched/sched_waking/trigger > > Instead of: > echo 'hist:key=pid:ts=common_timestamp.usecs' > > events/sched/sched_waking/trigger > > and the following crash happened: > > BUG: kernel NULL pointer dereference, address: 0000000000000008 > #PF: supervisor read access in kernel mode > #PF: error_code(0x0000) - not-present page > PGD 0 P4D 0 > Oops: 0000 [#1] PREEMPT SMP PTI > CPU: 4 PID: 1641 Comm: sh Not tainted 5.9.0-rc5-test+ #549 > Hardware name: Hewlett-Packard HP Compaq Pro 6300 SFF/339A, BIOS K01 > v03.03 07/14/2016 > RIP: 0010:event_hist_trigger_func+0x70b/0x1ee0 > Code: 24 08 89 d5 49 89 cc e9 8c 00 00 00 4c 89 f2 41 b9 00 10 00 00 > 4c 89 e1 44 89 ee 4c 89 ff e8 dc d3 ff ff 45 89 ea 4b 8b 14 d7 > 42 08 04 74 17 41 8b 8f c0 00 00 00 8d 71 01 41 89 b7 c0 00 00 > RSP: 0018:ffff959213d53db0 EFLAGS: 00010202 > RAX: ffffffffffffffea RBX: 0000000000000000 RCX: 0000000000084c04 > RDX: 0000000000000000 RSI: df7326aefebd174c RDI: 0000000000031080 > RBP: 0000000000000002 R08: 0000000000000001 R09: 0000000000000001 > R10: 0000000000000001 R11: 0000000000000046 R12: ffff959211dcf690 > R13: 0000000000000001 R14: ffff95925a36e370 R15: ffff959251c89800 > FS: 00007fb9ea934740(0000) GS:ffff95925ab00000(0000) > knlGS:0000000000000000 > CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > CR2: 0000000000000008 CR3: 00000000c976c005 CR4: 00000000001706e0 > Call Trace: > ? trigger_process_regex+0x78/0x110 > trigger_process_regex+0xc5/0x110 > event_trigger_write+0x71/0xd0 > vfs_write+0xca/0x210 > ksys_write+0x70/0xf0 > do_syscall_64+0x33/0x40 > entry_SYSCALL_64_after_hwframe+0x44/0xa9 > RIP: 0033:0x7fb9eaa29487 > Code: 64 89 02 48 c7 c0 ff ff ff ff eb bb 0f 1f 80 00 00 00 00 f3 0f > 1e fa 64 8b 04 25 18 00 00 00 85 c0 75 10 b8 01 00 00 00 0f 05 <48> > 3d 00 f0 ff ff 77 51 c3 48 83 ec 28 48 89 54 24 18 48 89 74 24 > > This was caused by accessing the hlist_data fields after the call to > __create_val_fields() without checking if the creation succeed. > > Fixes: 63a1e5de3006 ("tracing: Save normal string variables") Yes, this fixes the fix, sigh. Reviewed-by: Tom Zanussi Thanks, Tom > Signed-off-by: Steven Rostedt (VMware) > --- > kernel/trace/trace_events_hist.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/kernel/trace/trace_events_hist.c > b/kernel/trace/trace_events_hist.c > index c74a7d157306..96c3f86b81c5 100644 > --- a/kernel/trace/trace_events_hist.c > +++ b/kernel/trace/trace_events_hist.c > @@ -3687,7 +3687,7 @@ static int create_var_field(struct > hist_trigger_data *hist_data, > > ret = __create_val_field(hist_data, val_idx, file, var_name, > expr_str, flags); > > - if (hist_data->fields[val_idx]->flags & HIST_FIELD_FL_STRING) > + if (!ret && hist_data->fields[val_idx]->flags & > HIST_FIELD_FL_STRING) > hist_data->fields[val_idx]->var_str_idx = hist_data- > >n_var_str++; > > return ret;