From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=efficios.com header.i=@efficios.com header.b="N/XuIcIC" Received: from smtpout.efficios.com (smtpout.efficios.com [167.114.26.122]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 0A37DFE; Tue, 12 Dec 2023 06:33:12 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=efficios.com; s=smtpout1; t=1702391592; bh=T1FTOhn+dhe2RzQli+HA9sglh+MKVmt+QGRK16ISh8c=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=N/XuIcIC5n/F9LxFkbso1fomRmByzGSpVdY0yHcHKFnqc56Z86rthqwwb81hDbQLl Uh8IPawWVo14yvd+5h+t9oL5MpUcMABxKJvJCOUA+v7c/T9VrlbCAIfi6qNQA5FZJb vu7eezd4Ljb+IfozTCP+OVSwNa4NL6r2Whg4e/eb64BlCws/4+xQUj6Rp/Ocs/tWGW NojGDRAVm+4DhQjcTjQYdvGn2xCpkYo96ByDUx8Ae+2PrsEOJroGzjnqsLCT8Vd2ap noaa5PMANi+SrI26YYNlQvAFJUieMCy7Wk/S/PH7FJMvjCg2AHZQ5sXGw4a8aIIVBL hIFDB56U5nzsw== Received: from [172.16.0.134] (192-222-143-198.qc.cable.ebox.net [192.222.143.198]) by smtpout.efficios.com (Postfix) with ESMTPSA id 4SqLgr0zpNzGCv; Tue, 12 Dec 2023 09:33:12 -0500 (EST) Message-ID: <445ac00d-0f0c-4f6a-b85a-97209635c3f3@efficios.com> Date: Tue, 12 Dec 2023 09:33:11 -0500 Precedence: bulk X-Mailing-List: linux-trace-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2] tracing: Allow for max buffer data size trace_marker writes Content-Language: en-US To: Steven Rostedt , LKML , Linux Trace Kernel Cc: Masami Hiramatsu , Mark Rutland References: <20231212090057.41b28efe@gandalf.local.home> From: Mathieu Desnoyers In-Reply-To: <20231212090057.41b28efe@gandalf.local.home> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 2023-12-12 09:00, Steven Rostedt wrote: [...] > --- a/kernel/trace/trace.c > +++ b/kernel/trace/trace.c > @@ -7272,6 +7272,7 @@ tracing_mark_write(struct file *filp, const char __user *ubuf, > enum event_trigger_type tt = ETT_NONE; > struct trace_buffer *buffer; > struct print_entry *entry; > + int meta_size; > ssize_t written; > int size; > int len; > @@ -7286,12 +7287,9 @@ tracing_mark_write(struct file *filp, const char __user *ubuf, > if (!(tr->trace_flags & TRACE_ITER_MARKERS)) > return -EINVAL; > > - if (cnt > TRACE_BUF_SIZE) > - cnt = TRACE_BUF_SIZE; You're removing an early bound check for a size_t userspace input... > - > - BUILD_BUG_ON(TRACE_BUF_SIZE >= PAGE_SIZE); > - > - size = sizeof(*entry) + cnt + 2; /* add '\0' and possible '\n' */ > + meta_size = sizeof(*entry) + 2; /* add '\0' and possible '\n' */ > + again: > + size = cnt + meta_size; ... and then implicitly casting it into a "int" size variable, which can therefore become a negative value. Just for the sake of not having to rely on ring_buffer_lock_reserve catching (length > BUF_MAX_DATA_SIZE), I would recommend to add an early check for negative here. > > /* If less than "", then make sure we can still add that */ > if (cnt < FAULTED_SIZE) > @@ -7300,9 +7298,25 @@ tracing_mark_write(struct file *filp, const char __user *ubuf, > buffer = tr->array_buffer.buffer; > event = __trace_buffer_lock_reserve(buffer, TRACE_PRINT, size, > tracing_gen_ctx()); > - if (unlikely(!event)) > + if (unlikely(!event)) { > + /* > + * If the size was greated than what was allowed, then greater ? Thanks, Mathieu -- Mathieu Desnoyers EfficiOS Inc. https://www.efficios.com