From nobody Fri Dec 19 16:01:38 2025 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 82DFDC04A95 for ; Sat, 22 Oct 2022 08:10:57 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233144AbiJVIKy (ORCPT ); Sat, 22 Oct 2022 04:10:54 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:60216 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232796AbiJVIHt (ORCPT ); Sat, 22 Oct 2022 04:07:49 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id E90B92D6579; Sat, 22 Oct 2022 00:53:21 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 76D4F60B26; Sat, 22 Oct 2022 07:40:56 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 8CC58C433C1; Sat, 22 Oct 2022 07:40:55 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1666424455; bh=YDvdxWfV1FcnbZUuL8IYRGcSN1JzkaRyWuTjHwTihzY=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=GK8evJ0FDUeP4Jhudn9t76zU7vJSLzkjFbF5Vx4intRfW2oK01fTF008U4Z4ywTHq iL8vjDRVTCYxZlfbn4PtsnH7p2cBa4ioxgff2E+WqgryOzn3bAGVeEwMUmyPHIkesY dj1/sKLpiYI0eKunNoxO6Oc54dYCwZa6MA+uAT/k= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Andrew Morton , Tom Zanussi , "Masami Hiramatsu (Google)" , "Steven Rostedt (Google)" Subject: [PATCH 5.19 152/717] tracing: Fix reading strings from synthetic events Date: Sat, 22 Oct 2022 09:20:31 +0200 Message-Id: <20221022072442.334611786@linuxfoundation.org> X-Mailer: git-send-email 2.38.1 In-Reply-To: <20221022072415.034382448@linuxfoundation.org> References: <20221022072415.034382448@linuxfoundation.org> User-Agent: quilt/0.67 MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" From: Steven Rostedt (Google) commit 0934ae9977c27133449b6dd8c6213970e7eece38 upstream. The follow commands caused a crash: # cd /sys/kernel/tracing # echo 's:open char file[]' > dynamic_events # echo 'hist:keys=3Dcommon_pid:file=3Dfilename:onchange($file).trace(open= ,$file)' > events/syscalls/sys_enter_openat/trigger' # echo 1 > events/synthetic/open/enable BOOM! The problem is that the synthetic event field "char file[]" will read the value given to it as a string without any memory checks to make sure the address is valid. The above example will pass in the user space address and the sythetic event code will happily call strlen() on it and then strscpy() where either one will cause an oops when accessing user space addresses. Use the helper functions from trace_kprobe and trace_eprobe that can read strings safely (and actually succeed when the address is from user space and the memory is mapped in). Now the above can show: packagekitd-1721 [000] ...2. 104.597170: open: file=3D/usr/lib/rp= m/fileattrs/cmake.attr in:imjournal-978 [006] ...2. 104.599642: open: file=3D/var/lib/rs= yslog/imjournal.state.tmp packagekitd-1721 [000] ...2. 104.626308: open: file=3D/usr/lib/rp= m/fileattrs/debuginfo.attr Link: https://lkml.kernel.org/r/20221012104534.826549315@goodmis.org Cc: stable@vger.kernel.org Cc: Andrew Morton Cc: Tom Zanussi Acked-by: Masami Hiramatsu (Google) Reviewed-by: Tom Zanussi Fixes: bd82631d7ccdc ("tracing: Add support for dynamic strings to syntheti= c events") Signed-off-by: Steven Rostedt (Google) Signed-off-by: Greg Kroah-Hartman --- kernel/trace/trace_events_synth.c | 23 +++++++++++++++++------ 1 file changed, 17 insertions(+), 6 deletions(-) --- a/kernel/trace/trace_events_synth.c +++ b/kernel/trace/trace_events_synth.c @@ -17,6 +17,8 @@ /* for gfp flag names */ #include #include +#include "trace_probe.h" +#include "trace_probe_kernel.h" =20 #include "trace_synth.h" =20 @@ -409,6 +411,7 @@ static unsigned int trace_string(struct { unsigned int len =3D 0; char *str_field; + int ret; =20 if (is_dynamic) { u32 data_offset; @@ -417,19 +420,27 @@ static unsigned int trace_string(struct data_offset +=3D event->n_u64 * sizeof(u64); data_offset +=3D data_size; =20 - str_field =3D (char *)entry + data_offset; - - len =3D strlen(str_val) + 1; - strscpy(str_field, str_val, len); + len =3D kern_fetch_store_strlen((unsigned long)str_val); =20 data_offset |=3D len << 16; *(u32 *)&entry->fields[*n_u64] =3D data_offset; =20 + ret =3D kern_fetch_store_string((unsigned long)str_val, &entry->fields[*= n_u64], entry); + (*n_u64)++; } else { str_field =3D (char *)&entry->fields[*n_u64]; =20 - strscpy(str_field, str_val, STR_VAR_LEN_MAX); +#ifdef CONFIG_ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE + if ((unsigned long)str_val < TASK_SIZE) + ret =3D strncpy_from_user_nofault(str_field, str_val, STR_VAR_LEN_MAX); + else +#endif + ret =3D strncpy_from_kernel_nofault(str_field, str_val, STR_VAR_LEN_MAX= ); + + if (ret < 0) + strcpy(str_field, FAULT_STRING); + (*n_u64) +=3D STR_VAR_LEN_MAX / sizeof(u64); } =20 @@ -462,7 +473,7 @@ static notrace void trace_event_raw_even val_idx =3D var_ref_idx[field_pos]; str_val =3D (char *)(long)var_ref_vals[val_idx]; =20 - len =3D strlen(str_val) + 1; + len =3D kern_fetch_store_strlen((unsigned long)str_val); =20 fields_size +=3D len; }