perf maps: Get map before returning in maps__find_by_name

Finding a map is done under a lock, returning the map without a
reference count means it can be removed without notice and causing
uses after free. Grab a reference count to the map within the lock
region and return this. Fix up locations that need a map__put
following this. Also fix some reference counted pointer comparisons.
Signed-off-by: Ian Rogers <irogers@google.com>
Acked-by: Namhyung Kim <namhyung@kernel.org>
Cc: K Prateek Nayak <kprateek.nayak@amd.com>
Cc: James Clark <james.clark@arm.com>
Cc: Vincent Whitchurch <vincent.whitchurch@axis.com>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Cc: Colin Ian King <colin.i.king@gmail.com>
Cc: Changbin Du <changbin.du@huawei.com>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Song Liu <song@kernel.org>
Cc: Leo Yan <leo.yan@linux.dev>
Cc: Athira Rajeev <atrajeev@linux.vnet.ibm.com>
Cc: Liam Howlett <liam.howlett@oracle.com>
Cc: Artem Savkov <asavkov@redhat.com>
Cc: bpf@vger.kernel.org
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Link: https://lore.kernel.org/r/20240210031746.4057262-4-irogers@google.com

tools/perf/tests/vmlinux-kallsyms.c

@@ -131,9 +131,10 @@ static int test__vmlinux_matches_kallsyms_cb1(struct map *map, void *data)
 	struct map *pair = maps__find_by_name(args->kallsyms.kmaps,
 					(dso->kernel ? dso->short_name : dso->name));
 
-	if (pair)
+	if (pair) {
 		map__set_priv(pair, 1);
-	else {
+		map__put(pair);
+	} else {
 		if (!args->header_printed) {
 			pr_info("WARN: Maps only in vmlinux:\n");
 			args->header_printed = true;

tools/perf/util/machine.c

@@ -1537,8 +1537,10 @@ static int maps__set_module_path(struct maps *maps, const char *path, struct kmo
 		return 0;
 
 	long_name = strdup(path);
-	if (long_name == NULL)
+	if (long_name == NULL) {
+		map__put(map);
 		return -ENOMEM;
+	}
 
 	dso = map__dso(map);
 	dso__set_long_name(dso, long_name, true);
@@ -1552,7 +1554,7 @@ static int maps__set_module_path(struct maps *maps, const char *path, struct kmo
 		dso->symtab_type++;
 		dso->comp = m->comp;
 	}
-
+	map__put(map);
 	return 0;
 }
 

tools/perf/util/maps.c

@@ -905,7 +905,7 @@ struct map *maps__find_by_name(struct maps *maps, const char *name)
 			struct dso *dso = map__dso(maps__maps_by_name(maps)[i]);
 
 			if (dso && strcmp(dso->short_name, name) == 0) {
-				result = maps__maps_by_name(maps)[i]; // TODO: map__get
+				result = map__get(maps__maps_by_name(maps)[i]);
 				done = true;
 			}
 		}
@@ -917,7 +917,7 @@ struct map *maps__find_by_name(struct maps *maps, const char *name)
 					sizeof(*mapp), map__strcmp_name);
 
 			if (mapp) {
-				result = *mapp; // TODO: map__get
+				result = map__get(*mapp);
 				i = mapp - maps__maps_by_name(maps);
 				RC_CHK_ACCESS(maps)->last_search_by_name_idx = i;
 			}
@@ -942,7 +942,7 @@ struct map *maps__find_by_name(struct maps *maps, const char *name)
 					struct dso *dso = map__dso(pos);
 
 					if (dso && strcmp(dso->short_name, name) == 0) {
-						result = pos; // TODO: map__get
+						result = map__get(pos);
 						break;
 					}
 				}

tools/perf/util/probe-event.c

@@ -358,6 +358,7 @@ static int kernel_get_module_dso(const char *module, struct dso **pdso)
 		map = maps__find_by_name(machine__kernel_maps(host_machine), module_name);
 		if (map) {
 			dso = map__dso(map);
+			map__put(map);
 			goto found;
 		}
 		pr_debug("Failed to find module %s.\n", module);

tools/perf/util/symbol-elf.c

@@ -1535,8 +1535,10 @@ static int dso__process_kernel_symbol(struct dso *dso, struct map *map,
 		dso__set_loaded(curr_dso);
 		*curr_mapp = curr_map;
 		*curr_dsop = curr_dso;
-	} else
+	} else {
 		*curr_dsop = map__dso(curr_map);
+		map__put(curr_map);
+	}
 
 	return 0;
 }

tools/perf/util/symbol.c

@@ -814,7 +814,7 @@ static int maps__split_kallsyms(struct maps *kmaps, struct dso *dso, u64 delta,
 				struct map *initial_map)
 {
 	struct machine *machine;
-	struct map *curr_map = initial_map;
+	struct map *curr_map = map__get(initial_map);
 	struct symbol *pos;
 	int count = 0, moved = 0;
 	struct rb_root_cached *root = &dso->symbols;
@@ -858,13 +858,14 @@ static int maps__split_kallsyms(struct maps *kmaps, struct dso *dso, u64 delta,
 					dso__set_loaded(curr_map_dso);
 				}
 
+				map__zput(curr_map);
 				curr_map = maps__find_by_name(kmaps, module);
 				if (curr_map == NULL) {
 					pr_debug("%s/proc/{kallsyms,modules} "
 					         "inconsistency while looking "
 						 "for \"%s\" module!\n",
 						 machine->root_dir, module);
-					curr_map = initial_map;
+					curr_map = map__get(initial_map);
 					goto discard_symbol;
 				}
 				curr_map_dso = map__dso(curr_map);
@@ -888,7 +889,7 @@ static int maps__split_kallsyms(struct maps *kmaps, struct dso *dso, u64 delta,
 			 * symbols at this point.
 			 */
 			goto discard_symbol;
-		} else if (curr_map != initial_map) {
+		} else if (!RC_CHK_EQUAL(curr_map, initial_map)) {
 			char dso_name[PATH_MAX];
 			struct dso *ndso;
 
@@ -899,7 +900,8 @@ static int maps__split_kallsyms(struct maps *kmaps, struct dso *dso, u64 delta,
 			}
 
 			if (count == 0) {
-				curr_map = initial_map;
+				map__zput(curr_map);
+				curr_map = map__get(initial_map);
 				goto add_symbol;
 			}
 
@@ -913,6 +915,7 @@ static int maps__split_kallsyms(struct maps *kmaps, struct dso *dso, u64 delta,
 					kernel_range++);
 
 			ndso = dso__new(dso_name);
+			map__zput(curr_map);
 			if (ndso == NULL)
 				return -1;
 
@@ -926,6 +929,7 @@ static int maps__split_kallsyms(struct maps *kmaps, struct dso *dso, u64 delta,
 
 			map__set_mapping_type(curr_map, MAPPING_TYPE__IDENTITY);
 			if (maps__insert(kmaps, curr_map)) {
+				map__zput(curr_map);
 				dso__put(ndso);
 				return -1;
 			}
@@ -936,7 +940,7 @@ static int maps__split_kallsyms(struct maps *kmaps, struct dso *dso, u64 delta,
 			pos->end -= delta;
 		}
 add_symbol:
-		if (curr_map != initial_map) {
+		if (!RC_CHK_EQUAL(curr_map, initial_map)) {
 			struct dso *curr_map_dso = map__dso(curr_map);
 
 			rb_erase_cached(&pos->rb_node, root);
@@ -951,12 +955,12 @@ static int maps__split_kallsyms(struct maps *kmaps, struct dso *dso, u64 delta,
 		symbol__delete(pos);
 	}
 
-	if (curr_map != initial_map &&
+	if (!RC_CHK_EQUAL(curr_map, initial_map) &&
 	    dso->kernel == DSO_SPACE__KERNEL_GUEST &&
 	    machine__is_default_guest(maps__machine(kmaps))) {
 		dso__set_loaded(map__dso(curr_map));
 	}
-
+	map__put(curr_map);
 	return count + moved;
 }