[PATCH v3 11/16] tracing/filters: Check for trailing characters after newline in filter string

[Masami Hiramatsu (Google)]

From: Masami Hiramatsu (Google) <mhira...@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 called 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.

Introduce an internal function filter_check_newline() to convert the
first newline to NUL and check that the rest of the input contains no
non-whitespace characters. If any non-whitespace character follows the
newline, report it as an invalid input error (-EINVAL).

Signed-off-by: Masami Hiramatsu (Google) <mhira...@kernel.org>
---
Changes in v3:
 - Introduce filter_check_newline() to convert the first newline to
   NUL and reject any non-whitespace characters after the newline with
   an invalid input error (-EINVAL).
---
 kernel/trace/trace_events_filter.c |   37 ++++++++++++++++++++++++++++++++++++
 1 file changed, 37 insertions(+)

diff --git a/kernel/trace/trace_events_filter.c 
b/kernel/trace/trace_events_filter.c
index 9d1446464058..f3c18324b07a 100644
--- a/kernel/trace/trace_events_filter.c
+++ b/kernel/trace/trace_events_filter.c
@@ -2441,6 +2441,31 @@ static int process_system_preds(struct 
trace_subsystem_dir *dir,
        return -ENOMEM;
 }
 
+/*
+ * Convert the first newline to '\0' and check that the rest of the input
+ * contains no non-whitespace characters.
+ */
+static int filter_check_newline(char *str)
+{
+       char *p;
+
+       if (!str)
+               return 0;
+
+       p = strchr(str, '\n');
+       if (!p)
+               return 0;
+
+       *p++ = '\0';
+       while (*p) {
+               if (!isspace(*p))
+                       return -EINVAL;
+               p++;
+       }
+
+       return 0;
+}
+
 static int create_filter_start(char *filter_string, bool set_str,
                               struct filter_parse_error **pse,
                               struct event_filter **filterp)
@@ -2452,6 +2477,10 @@ static int create_filter_start(char *filter_string, bool 
set_str,
        if (WARN_ON_ONCE(*pse || *filterp))
                return -EINVAL;
 
+       err = filter_check_newline(filter_string);
+       if (err)
+               return err;
+
        filter = kzalloc_obj(*filter);
        if (filter && set_str) {
                filter->filter_string = kstrdup(filter_string, GFP_KERNEL);
@@ -2570,6 +2599,10 @@ int apply_event_filter(struct trace_event_file *file, 
char *filter_string)
        if (file->flags & EVENT_FILE_FL_FREED)
                return -ENODEV;
 
+       err = filter_check_newline(filter_string);
+       if (err)
+               return err;
+
        if (!strcmp(strstrip(filter_string), "0")) {
                filter_disable(file);
                filter = event_filter(file);
@@ -2624,6 +2657,10 @@ int apply_subsystem_event_filter(struct 
trace_subsystem_dir *dir,
        if (!dir->nr_events)
                return -ENODEV;
 
+       err = filter_check_newline(filter_string);
+       if (err)
+               return err;
+
        if (!strcmp(strstrip(filter_string), "0")) {
                filter_free_subsystem_preds(dir, tr);
                remove_filter_string(system->filter);