perf maps: Get map before returning in maps__find

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.

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/20240210031746.4057262-3-irogers@google.com

tools/perf/arch/x86/tests/dwarf-unwind.c

@@ -34,6 +34,7 @@ static int sample_ustack(struct perf_sample *sample,
 	}
 
 	stack_size = map__end(map) - sp;
+	map__put(map);
 	stack_size = stack_size > STACK_SIZE ? STACK_SIZE : stack_size;
 
 	memcpy(buf, (void *) sp, stack_size);

tools/perf/tests/vmlinux-kallsyms.c

@@ -151,10 +151,8 @@ static int test__vmlinux_matches_kallsyms_cb2(struct map *map, void *data)
 	u64 mem_end = map__unmap_ip(args->vmlinux_map, map__end(map));
 
 	pair = maps__find(args->kallsyms.kmaps, mem_start);
-	if (pair == NULL || map__priv(pair))
-		return 0;
 
-	if (map__start(pair) == mem_start) {
+	if (pair != NULL && !map__priv(pair) && map__start(pair) == mem_start) {
 		struct dso *dso = map__dso(map);
 
 		if (!args->header_printed) {
@@ -170,6 +168,7 @@ static int test__vmlinux_matches_kallsyms_cb2(struct map *map, void *data)
 		pr_info(" %s\n", dso->name);
 		map__set_priv(pair, 1);
 	}
+	map__put(pair);
 	return 0;
 }
 

tools/perf/util/bpf-event.c

@@ -63,6 +63,7 @@ static int machine__process_bpf_event_load(struct machine *machine,
 			dso->bpf_prog.id = id;
 			dso->bpf_prog.sub_id = i;
 			dso->bpf_prog.env = env;
+			map__put(map);
 		}
 	}
 	return 0;

tools/perf/util/event.c

@@ -511,7 +511,7 @@ size_t perf_event__fprintf_text_poke(union perf_event *event, struct machine *ma
 		struct addr_location al;
 
 		addr_location__init(&al);
-		al.map = map__get(maps__find(machine__kernel_maps(machine), tp->addr));
+		al.map = maps__find(machine__kernel_maps(machine), tp->addr);
 		if (al.map && map__load(al.map) >= 0) {
 			al.addr = map__map_ip(al.map, tp->addr);
 			al.sym = map__find_symbol(al.map, al.addr);
@@ -641,7 +641,7 @@ struct map *thread__find_map(struct thread *thread, u8 cpumode, u64 addr,
 		return NULL;
 	}
 	al->maps = maps__get(maps);
-	al->map = map__get(maps__find(maps, al->addr));
+	al->map = maps__find(maps, al->addr);
 	if (al->map != NULL) {
 		/*
 		 * Kernel maps might be changed when loading symbols so loading

tools/perf/util/machine.c

@@ -896,7 +896,6 @@ static int machine__process_ksymbol_register(struct machine *machine,
 	struct symbol *sym;
 	struct dso *dso;
 	struct map *map = maps__find(machine__kernel_maps(machine), event->ksymbol.addr);
-	bool put_map = false;
 	int err = 0;
 
 	if (!map) {
@@ -913,12 +912,6 @@ static int machine__process_ksymbol_register(struct machine *machine,
 			err = -ENOMEM;
 			goto out;
 		}
-		/*
-		 * The inserted map has a get on it, we need to put to release
-		 * the reference count here, but do it after all accesses are
-		 * done.
-		 */
-		put_map = true;
 		if (event->ksymbol.ksym_type == PERF_RECORD_KSYMBOL_TYPE_OOL) {
 			dso->binary_type = DSO_BINARY_TYPE__OOL;
 			dso->data.file_size = event->ksymbol.len;
@@ -952,7 +945,6 @@ static int machine__process_ksymbol_register(struct machine *machine,
 	}
 	dso__insert_symbol(dso, sym);
 out:
-	if (put_map)
 	map__put(map);
 	return err;
 }
@@ -977,7 +969,7 @@ static int machine__process_ksymbol_unregister(struct machine *machine,
 		if (sym)
 			dso__delete_symbol(dso, sym);
 	}
-
+	map__put(map);
 	return 0;
 }
 
@@ -1005,11 +997,11 @@ int machine__process_text_poke(struct machine *machine, union perf_event *event,
 		perf_event__fprintf_text_poke(event, machine, stdout);
 
 	if (!event->text_poke.new_len)
-		return 0;
+		goto out;
 
 	if (cpumode != PERF_RECORD_MISC_KERNEL) {
 		pr_debug("%s: unsupported cpumode - ignoring\n", __func__);
-		return 0;
+		goto out;
 	}
 
 	if (dso) {
@@ -1032,7 +1024,8 @@ int machine__process_text_poke(struct machine *machine, union perf_event *event,
 		pr_debug("Failed to find kernel text poke address map for %#" PRI_lx64 "\n",
 			 event->text_poke.addr);
 	}
-
+out:
+	map__put(map);
 	return 0;
 }
 
@@ -1300,9 +1293,10 @@ static int machine__map_x86_64_entry_trampolines_cb(struct map *map, void *data)
 		return 0;
 
 	dest_map = maps__find(args->kmaps, map__pgoff(map));
-	if (dest_map != map)
+	if (RC_CHK_ACCESS(dest_map) != RC_CHK_ACCESS(map))
 		map__set_pgoff(map, map__map_ip(dest_map, map__pgoff(map)));
 
+	map__put(dest_map);
 	args->found = true;
 	return 0;
 }

tools/perf/util/maps.c

@@ -506,15 +506,18 @@ void maps__remove_maps(struct maps *maps, bool (*cb)(struct map *map, void *data
 struct symbol *maps__find_symbol(struct maps *maps, u64 addr, struct map **mapp)
 {
 	struct map *map = maps__find(maps, addr);
+	struct symbol *result = NULL;
 
 	/* Ensure map is loaded before using map->map_ip */
 	if (map != NULL && map__load(map) >= 0) {
-		if (mapp != NULL)
+		if (mapp)
-			*mapp = map; // TODO: map_put on else path when find returns a get.
+			*mapp = map;
-		return map__find_symbol(map, map__map_ip(map, addr));
-	}
 
-	return NULL;
+		result = map__find_symbol(map, map__map_ip(map, addr));
+		if (!mapp)
+			map__put(map);
+	}
+	return result;
 }
 
 struct maps__find_symbol_by_name_args {
@@ -558,7 +561,7 @@ int maps__find_ams(struct maps *maps, struct addr_map_symbol *ams)
 	if (ams->addr < map__start(ams->ms.map) || ams->addr >= map__end(ams->ms.map)) {
 		if (maps == NULL)
 			return -1;
-		ams->ms.map = maps__find(maps, ams->addr);  // TODO: map_get
+		ams->ms.map = maps__find(maps, ams->addr);
 		if (ams->ms.map == NULL)
 			return -1;
 	}
@@ -868,7 +871,7 @@ struct map *maps__find(struct maps *maps, u64 ip)
 					sizeof(*mapp), map__addr_cmp);
 
 			if (mapp)
-				result = *mapp; // map__get(*mapp);
+				result = map__get(*mapp);
 			done = true;
 		}
 		up_read(maps__lock(maps));

tools/perf/util/symbol.c

@@ -757,7 +757,6 @@ static int dso__load_all_kallsyms(struct dso *dso, const char *filename)
 
 static int maps__split_kallsyms_for_kcore(struct maps *kmaps, struct dso *dso)
 {
-	struct map *curr_map;
 	struct symbol *pos;
 	int count = 0;
 	struct rb_root_cached old_root = dso->symbols;
@@ -770,6 +769,7 @@ static int maps__split_kallsyms_for_kcore(struct maps *kmaps, struct dso *dso)
 	*root = RB_ROOT_CACHED;
 
 	while (next) {
+		struct map *curr_map;
 		struct dso *curr_map_dso;
 		char *module;
 
@@ -796,6 +796,7 @@ static int maps__split_kallsyms_for_kcore(struct maps *kmaps, struct dso *dso)
 			pos->end -= map__start(curr_map) - map__pgoff(curr_map);
 		symbols__insert(&curr_map_dso->symbols, pos);
 		++count;
+		map__put(curr_map);
 	}
 
 	/* Symbols have been adjusted */