tracing: Add size check when printing trace_marker output

[ Upstream commit 60be76eeabb3d83858cc6577fc65c7d0f36ffd42 ]

If for some reason the trace_marker write does not have a nul byte for the
string, it will overflow the print:

  trace_seq_printf(s, ": %s", field->buf);

The field->buf could be missing the nul byte. To prevent overflow, add the
max size that the buf can be by using the event size and the field
location.

  int max = iter->ent_size - offsetof(struct print_entry, buf);

  trace_seq_printf(s, ": %*.s", max, field->buf);

Link: https://lore.kernel.org/linux-trace-kernel/20231212084444.4619b8ce@gandalf.local.home
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Reviewed-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/kernel/trace/trace_output.c b/kernel/trace/trace_output.c
index db57509..3b7d3e9 100644 (file)
--- a/kernel/trace/trace_output.c
+++ b/kernel/trace/trace_output.c
@@ -1587,11 +1587,12 @@ static enum print_line_t trace_print_print(struct trace_iterator *iter,
 {
        struct print_entry *field;
        struct trace_seq *s = &iter->seq;
+       int max = iter->ent_size - offsetof(struct print_entry, buf);
 
        trace_assign_type(field, iter->ent);
 
        seq_print_ip_sym(s, field->ip, flags);
-       trace_seq_printf(s, ": %s", field->buf);
+       trace_seq_printf(s, ": %.*s", max, field->buf);
 
        return trace_handle_return(s);
 }
@@ -1600,10 +1601,11 @@ static enum print_line_t trace_print_raw(struct trace_iterator *iter, int flags,
                                         struct trace_event *event)
 {
        struct print_entry *field;
+       int max = iter->ent_size - offsetof(struct print_entry, buf);
 
        trace_assign_type(field, iter->ent);
 
-       trace_seq_printf(&iter->seq, "# %lx %s", field->ip, field->buf);
+       trace_seq_printf(&iter->seq, "# %lx %.*s", field->ip, max, field->buf);
 
        return trace_handle_return(&iter->seq);
 }