Re: [PATCH v3 01/16] tracing/filters: Fix regex_match_end() for zero-length strings

On Wed, 28 Oct 2026 00:59:33 +0000, sashiko-bot@kernel.org [off-list ref] wrote:

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [Medium] tracing/filters: redundant check in regex_match_end() makes patch a no-op
--

commit 8e400c22f46c7fff9d91b8c8e837ab24dfa0f5cd
Author: Masami Hiramatsu (Google) [off-list ref]

tracing/filters: Fix regex_match_end() for zero-length strings

This commit adds an early return in regex_match_end() when len <= r->len to
avoid underflowing len - 1 and accessing the input string when len is 0 or
smaller than the pattern.

quoted

diff --git a/kernel/trace/trace_events_filter.c b/kernel/trace/trace_events_filter.c
index 5e74d2dae40a3..59a0d3ba72740 100644
--- a/kernel/trace/trace_events_filter.c
+++ b/kernel/trace/trace_events_filter.c

@@ -1075,8 +1075,12 @@ static int regex_match_middle(char *str, struct regex *r, int len)
 
 static int regex_match_end(char *str, struct regex *r, int len)
 {
-	int strlen = len - 1;
+	int strlen;
 
+	if (len <= r->len)
+		return 0;
+
+	strlen = len - 1;
 	if (strlen >= r->len &&
 	    memcmp(str + strlen - r->len, r->pattern, r->len) == 0)
 		return 1;

[Severity: Medium]
Does this change have any functional effect in regex_match_end() in
kernel/trace/trace_events_filter.c?

Oops, right. Please drop this patch. This is my fault (I suggested).

quoted

+	if (len <= r->len)

and

quoted

 	if (strlen >= r->len &&

are the same...

Thanks!

-- 
Masami Hiramatsu (Google) [off-list ref]