perf symbol: Fix uninitialized return value in symbols__find_by_name()

found_idx and s aren't initialized, so if no symbol is found then the
assert at the end will index off the end of the array causing a
segfault. The function also doesn't return NULL when the symbol isn't
found even if the assert passes. Fix it by initializing the values and
only setting them when something is found.

Fixes the following test failure:

  $ perf test 1
  1: vmlinux symtab matches kallsyms     : FAILED!

Fixes: 259dce9 ("perf symbol: Remove symbol_name_rb_node")
Signed-off-by: James Clark <[email protected]>
Acked-by: Ian Rogers <[email protected]>
Cc: Mark Rutland <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Adrian Hunter <[email protected]>
Cc: Arnaldo Carvalho de Melo <[email protected]>
Cc: Jiri Olsa <[email protected]>
Cc: Alexander Shishkin <[email protected]>
Cc: Ingo Molnar <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Namhyung Kim <[email protected]>

Author: James-A-Clark

tools/perf/util/symbol.c

@@ -495,7 +495,10 @@ static struct symbol *symbols__find_by_name(struct symbol *symbols[],
 					    size_t *found_idx)
 {
 	size_t i, lower = 0, upper = symbols_len;
-	struct symbol *s;
+	struct symbol *s = NULL;
+
+	if (found_idx)
+		*found_idx = SIZE_MAX;
 
 	if (!symbols_len)
 		return NULL;
@@ -504,8 +507,7 @@ static struct symbol *symbols__find_by_name(struct symbol *symbols[],
 		int cmp;
 
 		i = (lower + upper) / 2;
-		s = symbols[i];
-		cmp = symbol__match_symbol_name(s->name, name, includes);
+		cmp = symbol__match_symbol_name(symbols[i]->name, name, includes);
 
 		if (cmp > 0)
 			upper = i;
@@ -514,24 +516,24 @@ static struct symbol *symbols__find_by_name(struct symbol *symbols[],
 		else {
 			if (found_idx)
 				*found_idx = i;
+			s = symbols[i];
 			break;
 		}
 	}
-	if (includes != SYMBOL_TAG_INCLUDE__DEFAULT_ONLY) {
+	if (s && includes != SYMBOL_TAG_INCLUDE__DEFAULT_ONLY) {
 		/* return first symbol that has same name (if any) */
 		for (; i > 0; i--) {
 			struct symbol *tmp = symbols[i - 1];
 
 			if (!arch__compare_symbol_names(tmp->name, s->name)) {
 				if (found_idx)
 					*found_idx = i - 1;
+				s = tmp;
 			} else
 				break;
-
-			s = tmp;
 		}
 	}
-	assert(!found_idx || s == symbols[*found_idx]);
+	assert(!found_idx || !s || s == symbols[*found_idx]);
 	return s;
 }