[PATCH v2 8/9] tracing/filters: Terminate filter string at first newline

["Masami Hiramatsu (Google)" <mhiramat@kernel.org>]

From: Masami Hiramatsu (Google) <mhiramat@kernel.org>

Each trace event or subsystem only holds a single filter, and
append_filter_err() / tracing_log_err() caret placement assumes a
single-line filter string. However, apply_event_filter() and
apply_subsystem_event_filter() only call strstrip(), which strips
trailing newlines but leaves embedded newlines intact.

An embedded newline in a filter string (for example inside 'CPUS{0\n"}')
causes cpulist_parse() / bitmap_parselist() to treat '\n' as the end of
the cpulist and ignore trailing characters before '}', desynchronizing
quote tracking between calc_stack() and parse_pred() and misaligning
error_log caret reporting.

Terminate filter_string at the first '\n' in apply_event_filter(),
apply_subsystem_event_filter(), and create_filter_start() so only the
first line is parsed.

Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
---
 kernel/trace/trace_events_filter.c |   15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/kernel/trace/trace_events_filter.c b/kernel/trace/trace_events_filter.c
index 8d7fb6e9d7f8..14afcca7a444 100644
--- a/kernel/trace/trace_events_filter.c
+++ b/kernel/trace/trace_events_filter.c
@@ -2426,10 +2426,15 @@ static int create_filter_start(char *filter_string, bool set_str,
 	struct event_filter *filter;
 	struct filter_parse_error *pe = NULL;
 	int err = 0;
+	char *p;
 
 	if (WARN_ON_ONCE(*pse || *filterp))
 		return -EINVAL;
 
+	p = strchr(filter_string, '\n');
+	if (p)
+		*p = '\0';
+
 	filter = kzalloc_obj(*filter);
 	if (filter && set_str) {
 		filter->filter_string = kstrdup(filter_string, GFP_KERNEL);
@@ -2543,11 +2548,16 @@ int apply_event_filter(struct trace_event_file *file, char *filter_string)
 {
 	struct trace_event_call *call = file->event_call;
 	struct event_filter *filter = NULL;
+	char *p;
 	int err;
 
 	if (file->flags & EVENT_FILE_FL_FREED)
 		return -ENODEV;
 
+	p = strchr(filter_string, '\n');
+	if (p)
+		*p = '\0';
+
 	if (!strcmp(strstrip(filter_string), "0")) {
 		filter_disable(file);
 		filter = event_filter(file);
@@ -2595,6 +2605,7 @@ int apply_subsystem_event_filter(struct trace_subsystem_dir *dir,
 	struct trace_array *tr = dir->tr;
 	struct event_filter *filter = NULL;
 	int err = 0;
+	char *p;
 
 	guard(mutex)(&event_mutex);
 
@@ -2602,6 +2613,10 @@ int apply_subsystem_event_filter(struct trace_subsystem_dir *dir,
 	if (!dir->nr_events)
 		return -ENODEV;
 
+	p = strchr(filter_string, '\n');
+	if (p)
+		*p = '\0';
+
 	if (!strcmp(strstrip(filter_string), "0")) {
 		filter_free_subsystem_preds(dir, tr);
 		remove_filter_string(system->filter);