From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp-bc09.mail.infomaniak.ch (smtp-bc09.mail.infomaniak.ch [45.157.188.9]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 078B943CE70 for ; Wed, 22 Jul 2026 17:12:32 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=45.157.188.9 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784740358; cv=none; b=PnnzUzmfVYjmPC8y3IyUxDIZDtzKj/Q2tuzwvsrGo9GRbIgvLygFl4O8rWP4fcnzzzMMkCjeOCRNQThGKGJUgyyCT8zPWPSxOtqdOvIkaiUtEmAjnumgL3fkRQm2cOSZpYlNK0sbx0n5rrhhZgDrM0NEDGqDz1GxzFgo04luPJw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784740358; c=relaxed/simple; bh=eA64fAcu3eda68Ms6cMpv3Np2q2Rp7OU/6aMwgsQg98=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=hO3++ry9ekj395KPSEak1SNv11DSIbxg8OaH9Ui1WM9CScOUP5HALMyiq4zaZNCNvwaFmwggrnXQHQlGHEEBwJfbPxd2ApWaWgRZ6bEe5kxFkIgLV912ExeNduQ6OZ/HbtehjMzwPZlCyaMFkWUZburzLEXnAtV6dkVgFmtBY0c= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=digikod.net; spf=pass smtp.mailfrom=digikod.net; dkim=pass (1024-bit key) header.d=digikod.net header.i=@digikod.net header.b=NehlVoUe; arc=none smtp.client-ip=45.157.188.9 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=digikod.net Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=digikod.net Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=digikod.net header.i=@digikod.net header.b="NehlVoUe" Received: from smtp-4-0001.mail.infomaniak.ch (smtp-4-0001.mail.infomaniak.ch [10.7.10.108]) by smtp-4-3000.mail.infomaniak.ch (Postfix) with ESMTPS id 4h515f6Yn0zrkJ; Wed, 22 Jul 2026 19:12:22 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=digikod.net; s=20191114; t=1784740342; bh=lbAK7cLdqqWUFp03v03vs6BR7pLRrduEWKGnD5D39Ik=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=NehlVoUeLewKAzdkrwMIG872kL0MbDF3BGM1LiQvz8gXjW2xI9KD/shnEBmqy2NtN UdDpFyqrW2VTK5jUq7ThH4o3p3hzuxUZ1W1XXmH/QwSMGt1mFBurE/kieL7GfmkcC1 byFBMbxeXqmyal3sxe3EPVXTBsgGD9D7Nz9UoxWc= Received: from unknown by smtp-4-0001.mail.infomaniak.ch (Postfix) with ESMTPA id 4h515d675kzy18; Wed, 22 Jul 2026 19:12:21 +0200 (CEST) From: =?UTF-8?q?Micka=C3=ABl=20Sala=C3=BCn?= To: =?UTF-8?q?G=C3=BCnther=20Noack?= , Steven Rostedt Cc: =?UTF-8?q?Micka=C3=ABl=20Sala=C3=BCn?= , Christian Brauner , Jann Horn , Jeff Xu , Justin Suess , Kees Cook , Masami Hiramatsu , Mathieu Desnoyers , Matthieu Buffet , Mikhail Ivanov , Tingmao Wang , kernel-team@cloudflare.com, linux-security-module@vger.kernel.org, linux-trace-kernel@vger.kernel.org Subject: [PATCH v3 07/20] tracing: Add __print_untrusted_str() Date: Wed, 22 Jul 2026 19:11:39 +0200 Message-ID: <20260722171159.2776765-8-mic@digikod.net> In-Reply-To: <20260722171159.2776765-1-mic@digikod.net> References: <20260722171159.2776765-1-mic@digikod.net> Precedence: bulk X-Mailing-List: linux-trace-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Infomaniak-Routing: alpha Landlock tracepoints expose filesystem paths and process names that may contain spaces, equal signs, or other characters that break ftrace field parsing. Add a __print_untrusted_str() TP_printk helper that escapes separators (space, equal sign), quotes, backslashes, and non-printable bytes via string_escape_mem(), so an untrusted string cannot inject field separators or control characters into the ftrace output and can be unambiguously recovered. This guarantee applies to the in-kernel ftrace text output (trace, trace_pipe). Userspace libtraceevent (perf, trace-cmd) does not yet parse this helper, so a companion libtraceevent change is needed for those consumers to pretty-print the field. Cc: Günther Noack Cc: Masami Hiramatsu Cc: Mathieu Desnoyers Cc: Steven Rostedt Cc: Tingmao Wang Signed-off-by: Mickaël Salaün --- Changes since v2: https://patch.msgid.link/20260406143717.1815792-6-mic@digikod.net - Add a Return: kdoc for trace_print_untrusted_str_seq() and rename its declaration parameter to src. Changes since v1: https://patch.msgid.link/20250523165741.693976-4-mic@digikod.net - Remove WARN_ON() (pointed out by Steven Rostedt). --- include/linux/trace_events.h | 2 + include/trace/stages/stage3_trace_output.h | 4 ++ include/trace/stages/stage7_class_define.h | 1 + kernel/trace/trace_output.c | 44 ++++++++++++++++++++++ 4 files changed, 51 insertions(+) diff --git a/include/linux/trace_events.h b/include/linux/trace_events.h index 308c76b57d13..4ece9b8d9d6b 100644 --- a/include/linux/trace_events.h +++ b/include/linux/trace_events.h @@ -60,6 +60,8 @@ trace_print_hex_dump_seq(struct trace_seq *p, const char *prefix_str, int prefix_type, int rowsize, int groupsize, const void *buf, size_t len, bool ascii); +const char *trace_print_untrusted_str_seq(struct trace_seq *s, const char *src); + int trace_raw_output_prep(struct trace_iterator *iter, struct trace_event *event); extern __printf(2, 3) diff --git a/include/trace/stages/stage3_trace_output.h b/include/trace/stages/stage3_trace_output.h index 181b81335781..0235dbd11b52 100644 --- a/include/trace/stages/stage3_trace_output.h +++ b/include/trace/stages/stage3_trace_output.h @@ -133,6 +133,10 @@ trace_print_hex_dump_seq(p, prefix_str, prefix_type, \ rowsize, groupsize, buf, len, ascii) +#undef __print_untrusted_str +#define __print_untrusted_str(str) \ + trace_print_untrusted_str_seq(p, __get_str(str)) + #undef __print_ns_to_secs #define __print_ns_to_secs(value) \ ({ \ diff --git a/include/trace/stages/stage7_class_define.h b/include/trace/stages/stage7_class_define.h index 47008897a795..f29a82e7a4c4 100644 --- a/include/trace/stages/stage7_class_define.h +++ b/include/trace/stages/stage7_class_define.h @@ -24,6 +24,7 @@ #undef __print_array #undef __print_dynamic_array #undef __print_hex_dump +#undef __print_untrusted_str #undef __get_buf #undef __event_in_hardirq diff --git a/kernel/trace/trace_output.c b/kernel/trace/trace_output.c index a5ad76175d10..f0a9b29b3e36 100644 --- a/kernel/trace/trace_output.c +++ b/kernel/trace/trace_output.c @@ -16,6 +16,7 @@ #include #include #include +#include #include "trace_output.h" #include "trace_btf.h" @@ -325,6 +326,49 @@ trace_print_hex_dump_seq(struct trace_seq *p, const char *prefix_str, } EXPORT_SYMBOL(trace_print_hex_dump_seq); +/** + * trace_print_untrusted_str_seq - print a string after escaping characters + * @s: trace seq struct to write to + * @src: The string to print + * + * Prints a string to a trace seq after escaping all special characters, + * including common separators (space, equal sign), quotes, and backslashes. + * This transforms a string from an untrusted source (e.g. user space) to make + * it: + * - safe to parse, + * - easy to read (for simple strings), + * - easy to get back the original. + * + * Return: A pointer to the escaped string within the trace seq buffer, or + * %NULL if @src is %NULL or the buffer is exhausted. + */ +const char *trace_print_untrusted_str_seq(struct trace_seq *s, + const char *src) +{ + int escaped_size; + char *buf; + size_t buf_size = seq_buf_get_buf(&s->seq, &buf); + const char *ret = trace_seq_buffer_ptr(s); + + /* Buffer exhaustion is normal when the trace buffer is full. */ + if (!src || buf_size == 0) + return NULL; + + escaped_size = string_escape_mem(src, strlen(src), buf, buf_size, + ESCAPE_SPACE | ESCAPE_SPECIAL | ESCAPE_NAP | ESCAPE_APPEND | + ESCAPE_OCTAL, " ='\"\\"); + if (unlikely(escaped_size >= buf_size)) { + /* We need some room for the final '\0'. */ + seq_buf_set_overflow(&s->seq); + s->full = 1; + return NULL; + } + seq_buf_commit(&s->seq, escaped_size); + trace_seq_putc(s, 0); + return ret; +} +EXPORT_SYMBOL(trace_print_untrusted_str_seq); + int trace_raw_output_prep(struct trace_iterator *iter, struct trace_event *trace_event) { -- 2.54.0