On Sun, 25 Oct 2026 01:25:33 +0900 "Masami Hiramatsu (Google)" <[email protected]> wrote:
> From: Masami Hiramatsu (Google) <[email protected]> > > regex_match_end() calculated string length as "len - 1", assuming @len is > the string length including trailing '\0'. However, for fixed-size string > fields, filter_pred_string() passes field->size as @len, and for "comm", > filter_pred_comm() passes TASK_COMM_LEN as @len. > > Because @len in these cases represents the buffer capacity rather than the > actual length of the string, regex_match_end() tests against the tail of > the buffer (typically trailing '\0' padding) rather than the end of the > string. Furthermore, if @len is 0 (denoting a dynamic string ending with > '\0'), "len - 1" underflows to -1 and never matches. > > Compute the actual string length using strnlen(str, len) when @len is > non-zero, and strlen(str) when @len is zero. > > Fixes: a3291c14ecf0 ("tracing/filters: Fix MATCH_END_ONLY filter matching") > Cc: [email protected] > Signed-off-by: Masami Hiramatsu (Google) <[email protected]> > --- > kernel/trace/trace_events_filter.c | 6 +++--- > 1 file changed, 3 insertions(+), 3 deletions(-) > > diff --git a/kernel/trace/trace_events_filter.c > b/kernel/trace/trace_events_filter.c > index 5e74d2dae40a..18ce3ec00d34 100644 > --- a/kernel/trace/trace_events_filter.c > +++ b/kernel/trace/trace_events_filter.c > @@ -1075,10 +1075,10 @@ 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 slen = len ? strnlen(str, len) : strlen(str); > > - if (strlen >= r->len && > - memcmp(str + strlen - r->len, r->pattern, r->len) == 0) > + if (slen >= r->len && > + memcmp(str + slen - r->len, r->pattern, r->len) == 0) > return 1; This slows down the code as it adds more strlen() calculations (it could have already been done. Let's fix the callers instead and have them pass in the real length. -- Steve > return 0; > }
