From: "Steven Rostedt (Google)" <rost...@goodmis.org>

[ 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/20231212084444.4619b...@gandalf.local.home

Cc: Mark Rutland <mark.rutl...@arm.com>
Cc: Mathieu Desnoyers <mathieu.desnoy...@efficios.com>
Reviewed-by: Masami Hiramatsu (Google) <mhira...@kernel.org>
Signed-off-by: Steven Rostedt (Google) <rost...@goodmis.org>
Signed-off-by: Sasha Levin <sas...@kernel.org>
---
 kernel/trace/trace_output.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/kernel/trace/trace_output.c b/kernel/trace/trace_output.c
index 94b0991717b6d..753b84c50848a 100644
--- a/kernel/trace/trace_output.c
+++ b/kernel/trace/trace_output.c
@@ -1313,11 +1313,12 @@ 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);
 }
@@ -1326,10 +1327,11 @@ 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);
 }
-- 
2.43.0


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