[PATCH v4 04/15] tracing/filters: Report parse error on all -EINVAL paths in filter parsing

[Masami Hiramatsu (Google)]

From: Masami Hiramatsu (Google) <mhira...@kernel.org>

Several error paths in filter parsing return -EINVAL (or -1) without
calling parse_error() to set pe->lasterr:

1. In parse_pred(), when an invalid token is encountered where a field name
   is expected (e.g., "common_pid == 1 || (common_pid == 2 && )"), len is 0
   and it returns -1 without calling parse_error().
2. In process_preds(), when !nr_preds (e.g., empty or whitespace-only
   filter), it returns -EINVAL before predicate_parse() can set
   FILT_ERR_NO_FILTER.
3. In predicate_parse(), when op_stack overflows or the jump target check
   fails, it returns -EINVAL without calling parse_error().

Because pe->lasterr remains 0 on these paths, append_filter_err() falls
back to printing an uninformative "Error: (0)" instead of reporting the
diagnostic and error position.

Call parse_error() with the appropriate error code on all of these paths.

Fixes: 80765597bc58 ("tracing: Rewrite filter logic to be simpler and faster")
Cc: sta...@vger.kernel.org
Signed-off-by: Masami Hiramatsu (Google) <mhira...@kernel.org>
---
 kernel/trace/trace_events_filter.c |   13 ++++++++++---
 1 file changed, 10 insertions(+), 3 deletions(-)

diff --git a/kernel/trace/trace_events_filter.c 
b/kernel/trace/trace_events_filter.c
index 3f0c73819365..b8d765ca9f1a 100644
--- a/kernel/trace/trace_events_filter.c
+++ b/kernel/trace/trace_events_filter.c
@@ -515,6 +515,8 @@ predicate_parse(const char *str, int nr_parens, int 
nr_preds,
                switch (*next) {
                case '(':                                       /* #2 */
                        if (top - op_stack > nr_parens) {
+                               parse_error(pe, FILT_ERR_TOO_MANY_OPEN,
+                                           next - str);
                                ret = -EINVAL;
                                goto out_free;
                        }
@@ -638,6 +640,7 @@ predicate_parse(const char *str, int nr_parens, int 
nr_preds,
                prog[i].when_to_branch = invert;
                /* Make sure the program always moves forward */
                if (WARN_ON(prog[i].target <= i)) {
+                       parse_error(pe, FILT_ERR_INVALID_FILTER, 0);
                        ret = -EINVAL;
                        goto out_free;
                }
@@ -1709,8 +1712,10 @@ static int parse_pred(const char *str, void *data,
 
        len = i - s;
 
-       if (!len)
-               return -1;
+       if (!len) {
+               parse_error(pe, FILT_ERR_INVALID_FILTER, pos + i);
+               return -EINVAL;
+       }
 
        field_name = kmemdup_nul(str + s, len, GFP_KERNEL);
        if (!field_name)
@@ -2306,8 +2311,10 @@ static int process_preds(struct trace_event_call *call,
                return ret;
        }
 
-       if (!nr_preds)
+       if (!nr_preds) {
+               parse_error(pe, FILT_ERR_NO_FILTER, 0);
                return -EINVAL;
+       }
 
        prog = predicate_parse(filter_string, nr_parens, nr_preds,
                               parse_pred, call, pe);