On Mon, 26 Oct 2026 09:54:41 -0400, Steven Rostedt <[email protected]> wrote: > 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.
I sent v2 already, which is slightly lighter (but still using strnlen) https://lore.kernel.org/all/179291743946.492959.9624495647021680807.stgit@devnote2/ (anyway, 3/10 is already fixed as Sashiko mentioned.) > > Let's fix the callers instead and have them pass in the real length. OK, let me check it. Thanks, -- Masami Hiramatsu (Google) <[email protected]>
