From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from relay.hostedemail.com (smtprelay0011.hostedemail.com [216.40.44.11]) (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 6240536C9C1; Sun, 29 Mar 2026 18:48:49 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=216.40.44.11 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1774810131; cv=none; b=C0zwXhXQ6y8ntWg+oxM+uhDKKdTHte8uSmL1ZJLyJZMiPHJ9Sh+fqz9XizEN+PFDE4TzATHu1rppHAXVdqk4uRsXPgckxuggKAXFgtFKprBDdv0puAf2oq727JvHvPtnKvqiyxiSQdYDejn7F8CevBFel0v+TVuvVeY8IWAlx20= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1774810131; c=relaxed/simple; bh=oBFIfXp5lQAp915nPhmlHS+Wpla6OlTbZx/45OLvopc=; h=Date:From:To:Cc:Subject:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=OOPKqXixcjzGW21SqTQavJqpWOEoECl54ffmkyPwllFTNE0L6QHCUv8aCNz3a52AGRIy+33kOp4CSzuMCb6Iz43Gzl5NCQKPhCC1VIMm0cF1WUnSf+VecYkDXp6RHmqHJ+rMPmxsYi/7wPlNv2cn+OC4C8agqDbD9W84jUV41XU= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=goodmis.org; spf=pass smtp.mailfrom=goodmis.org; arc=none smtp.client-ip=216.40.44.11 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=goodmis.org Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=goodmis.org Received: from omf08.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay01.hostedemail.com (Postfix) with ESMTP id EC3C9E0857; Sun, 29 Mar 2026 18:48:47 +0000 (UTC) Received: from [HIDDEN] (Authenticated sender: rostedt@goodmis.org) by omf08.hostedemail.com (Postfix) with ESMTPA id 1F81B20029; Sun, 29 Mar 2026 18:48:46 +0000 (UTC) Date: Sun, 29 Mar 2026 14:49:39 -0400 From: Steven Rostedt To: Pengpeng Hou Cc: mhiramat@kernel.org, mathieu.desnoyers@efficios.com, tom.zanussi@linux.intel.com, linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org Subject: Re: [PATCH 2/2] tracing/hist: allocate synthetic-field command buffers to fit Message-ID: <20260329144939.55cdf935@gandalf.local.home> In-Reply-To: <20260329030950.32503-2-pengpeng@iscas.ac.cn> References: <20260329030950.32503-2-pengpeng@iscas.ac.cn> X-Mailer: Claws Mail 3.20.0git84 (GTK+ 2.24.33; x86_64-pc-linux-gnu) 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=US-ASCII Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: 1F81B20029 X-Rspamd-Server: rspamout06 X-Stat-Signature: iujhnd6jqeyb44y5t77o7ntqt4ahexig X-Session-Marker: 726F737465647440676F6F646D69732E6F7267 X-Session-ID: U2FsdGVkX18Op/iMd74LZtqGLyQguq0SqPH9sjEwYaI= X-HE-Tag: 1774810126-128758 X-HE-Meta: U2FsdGVkX19a+eWGLJDzLlZw9M7UFVvH+qL8agt3avS7Yh7QYfz3K1kfy6r156Zlzv3k+6giX/KRFuIKgIuWYUammQaEXaQmSNFnA5mMV/84KDoi8vGZfjz78mygng4rbB6X/tOMXxl7Ktm/cH7SVs8+sE4PDt8qLrbqhYJwIZjdrqwhKwE8erj/S4n6lVg9XK5lgHdbJ/+oW7e/SCKlJCOq/xr5BXjmw1Dc+QqHvBmAPhtO1TRBSQNLFapbQmEpWNV+vNn+gXujr9OrrZqMyPCkRXA3xd1tw72AR1WREew5YZd9rDYP7qrQaSoI/zXq On Sun, 29 Mar 2026 11:09:50 +0800 Pengpeng Hou wrote: > The synthetic field helpers currently build temporary names and trigger > commands in fixed MAX_FILTER_STR_VAL buffers with strcpy() and strcat(). > Long field names, key lists, or saved filters can therefore overrun > those staging buffers while constructing the synthetic histogram > command. > > Allocate the synthetic name and command buffers to the exact size > required by the current histogram instead of relying on fixed-size > scratch storage. No, the names should never be greater than the max value defined. If they are, then it should error out. > > Fixes: 02205a6752f2 ("tracing: Add support for 'field variables'") > Signed-off-by: Pengpeng Hou > --- > kernel/trace/trace_events_hist.c | 46 +++++++++++++++++++------------- > 1 file changed, 28 insertions(+), 18 deletions(-) > > diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c > index 4a27da628a71..1883bd6d9b95 100644 > --- a/kernel/trace/trace_events_hist.c > +++ b/kernel/trace/trace_events_hist.c > @@ -2964,13 +2964,10 @@ find_synthetic_field_var(struct hist_trigger_data *target_hist_data, > struct hist_field *event_var; > char *synthetic_name; > Should be preceded with: if (strlen("synthetic_") + strlen(field_name) >= MAX_FILTER_STR_VAL) return ERR_PTR(-E2BIG); > - synthetic_name = kzalloc(MAX_FILTER_STR_VAL, GFP_KERNEL); > + synthetic_name = kasprintf(GFP_KERNEL, "synthetic_%s", field_name); > if (!synthetic_name) > return ERR_PTR(-ENOMEM); > > - strcpy(synthetic_name, "synthetic_"); > - strcat(synthetic_name, field_name); > - > event_var = find_event_var(target_hist_data, system, event_name, synthetic_name); > > kfree(synthetic_name); > @@ -3016,6 +3013,8 @@ create_field_var_hist(struct hist_trigger_data *target_hist_data, > struct hist_field *event_var; > char *saved_filter; > char *cmd; > + size_t cmdlen; > + size_t off; > int ret; > > if (target_hist_data->n_field_var_hists >= SYNTH_FIELDS_MAX) { > @@ -3053,35 +3052,46 @@ create_field_var_hist(struct hist_trigger_data *target_hist_data, > if (!var_hist) > return ERR_PTR(-ENOMEM); > > - cmd = kzalloc(MAX_FILTER_STR_VAL, GFP_KERNEL); > + saved_filter = find_trigger_filter(hist_data, file); > + > + cmdlen = strlen("keys=") + strlen(":synthetic_") + > + strlen(field_name) + strlen("=") + strlen(field_name) + 1; > + first = true; > + for_each_hist_key_field(i, hist_data) { > + key_field = hist_data->fields[i]; > + if (!first) > + cmdlen++; > + cmdlen += strlen(key_field->field->name); > + first = false; > + } > + > + if (saved_filter) > + cmdlen += strlen(" if ") + strlen(saved_filter); > + Length should be checked. There shouldn't be huge strings for filters. Perhaps in the future we may make them bigger but for now, 256 bytes should be the limit. -- Steve > + cmd = kzalloc(cmdlen, GFP_KERNEL); > if (!cmd) { > kfree(var_hist); > return ERR_PTR(-ENOMEM); > } > > /* Use the same keys as the compatible histogram */ > - strcat(cmd, "keys="); > + off = scnprintf(cmd, cmdlen, "keys="); > + first = true; > > for_each_hist_key_field(i, hist_data) { > key_field = hist_data->fields[i]; > - if (!first) > - strcat(cmd, ","); > - strcat(cmd, key_field->field->name); > + off += scnprintf(cmd + off, cmdlen - off, "%s%s", > + first ? "" : ",", > key_field->field->name); first = false; > } > > /* Create the synthetic field variable specification */ > - strcat(cmd, ":synthetic_"); > - strcat(cmd, field_name); > - strcat(cmd, "="); > - strcat(cmd, field_name); > + off += scnprintf(cmd + off, cmdlen - off, ":synthetic_%s=%s", > + field_name, field_name); > > /* Use the same filter as the compatible histogram */ > - saved_filter = find_trigger_filter(hist_data, file); > - if (saved_filter) { > - strcat(cmd, " if "); > - strcat(cmd, saved_filter); > - } > + if (saved_filter) > + scnprintf(cmd + off, cmdlen - off, " if %s", > saved_filter); > var_hist->cmd = kstrdup(cmd, GFP_KERNEL); > if (!var_hist->cmd) {