Allocate temporary strings to hold dbus paths on the heap

Paths are limited to BUS_PATH_SIZE_MAX but the maximum size is anyway too big
to be allocated on the stack, so let's switch to the heap where there is a
clear way to understand if the allocation fails.

(cherry-picked from commit f519a19bcd5afe674a9b8fc462cd77d8bad403c1)

Related: #1678641

1 files changed, 54 insertions, 14 deletions

diff --git a/src/libsystemd/sd-bus/bus-objects.c b/src/libsystemd/sd-bus/bus-objects.c
index a18ff88b07..53bf0fd620 100644
--- a/src/libsystemd/sd-bus/bus-objects.c
+++ b/src/libsystemd/sd-bus/bus-objects.c
@@ -1134,7 +1134,8 @@ static int object_manager_serialize_path_and_fallbacks(
                 const char *path,
                 sd_bus_error *error) {
 
-        char *prefix;
+        _cleanup_free_ char *prefix = NULL;
+        size_t pl;
         int r;
 
         assert(bus);
@@ -1150,7 +1151,12 @@ static int object_manager_serialize_path_and_fallbacks(
                 return 0;
 
         /* Second, add fallback vtables registered for any of the prefixes */
-        prefix = alloca(strlen(path) + 1);
+        pl = strlen(path);
+        assert(pl <= BUS_PATH_SIZE_MAX);
+        prefix = new(char, pl + 1);
+        if (!prefix)
+                return -ENOMEM;
+
         OBJECT_PATH_FOREACH_PREFIX(prefix, path) {
                 r = object_manager_serialize_path(bus, reply, prefix, path, true, error);
                 if (r < 0)
@@ -1346,6 +1352,7 @@ static int object_find_and_run(
 }
 
 int bus_process_object(sd_bus *bus, sd_bus_message *m) {
+        _cleanup_free_ char *prefix = NULL;
         int r;
         size_t pl;
         bool found_object = false;
@@ -1370,9 +1377,12 @@ int bus_process_object(sd_bus *bus, sd_bus_message *m) {
         assert(m->member);
 
         pl = strlen(m->path);
-        do {
-                char prefix[pl+1];
+        assert(pl <= BUS_PATH_SIZE_MAX);
+        prefix = new(char, pl + 1);
+        if (!prefix)
+                return -ENOMEM;
 
+        do {
                 bus->nodes_modified = false;
 
                 r = object_find_and_run(bus, m, m->path, false, &found_object);
@@ -1499,9 +1509,15 @@ static int bus_find_parent_object_manager(sd_bus *bus, struct node **out, const
 
         n = hashmap_get(bus->nodes, path);
         if (!n) {
-                char *prefix;
+                _cleanup_free_ char *prefix = NULL;
+                size_t pl;
+
+                pl = strlen(path);
+                assert(pl <= BUS_PATH_SIZE_MAX);
+                prefix = new(char, pl + 1);
+                if (!prefix)
+                        return -ENOMEM;
 
-                prefix = alloca(strlen(path) + 1);
                 OBJECT_PATH_FOREACH_PREFIX(prefix, path) {
                         n = hashmap_get(bus->nodes, prefix);
                         if (n)
@@ -2090,8 +2106,9 @@ _public_ int sd_bus_emit_properties_changed_strv(
                 const char *interface,
                 char **names) {
 
+        _cleanup_free_ char *prefix = NULL;
         bool found_interface = false;
-        char *prefix;
+        size_t pl;
         int r;
 
         assert_return(bus, -EINVAL);
@@ -2112,6 +2129,12 @@ _public_ int sd_bus_emit_properties_changed_strv(
 
         BUS_DONT_DESTROY(bus);
 
+        pl = strlen(path);
+        assert(pl <= BUS_PATH_SIZE_MAX);
+        prefix = new(char, pl + 1);
+        if (!prefix)
+                return -ENOMEM;
+
         do {
                 bus->nodes_modified = false;
 
@@ -2121,7 +2144,6 @@ _public_ int sd_bus_emit_properties_changed_strv(
                 if (bus->nodes_modified)
                         continue;
 
-                prefix = alloca(strlen(path) + 1);
                 OBJECT_PATH_FOREACH_PREFIX(prefix, path) {
                         r = emit_properties_changed_on_interface(bus, prefix, path, interface, true, &found_interface, names);
                         if (r != 0)
@@ -2253,7 +2275,8 @@ static int object_added_append_all_prefix(
 
 static int object_added_append_all(sd_bus *bus, sd_bus_message *m, const char *path) {
         _cleanup_set_free_ Set *s = NULL;
-        char *prefix;
+        _cleanup_free_ char *prefix = NULL;
+        size_t pl;
         int r;
 
         assert(bus);
@@ -2298,7 +2321,12 @@ static int object_added_append_all(sd_bus *bus, sd_bus_message *m, const char *p
         if (bus->nodes_modified)
                 return 0;
 
-        prefix = alloca(strlen(path) + 1);
+        pl = strlen(path);
+        assert(pl <= BUS_PATH_SIZE_MAX);
+        prefix = new(char, pl + 1);
+        if (!prefix)
+                return -ENOMEM;
+
         OBJECT_PATH_FOREACH_PREFIX(prefix, path) {
                 r = object_added_append_all_prefix(bus, m, s, prefix, path, true);
                 if (r < 0)
@@ -2437,7 +2465,8 @@ static int object_removed_append_all_prefix(
 
 static int object_removed_append_all(sd_bus *bus, sd_bus_message *m, const char *path) {
         _cleanup_set_free_ Set *s = NULL;
-        char *prefix;
+        _cleanup_free_ char *prefix = NULL;
+        size_t pl;
         int r;
 
         assert(bus);
@@ -2469,7 +2498,12 @@ static int object_removed_append_all(sd_bus *bus, sd_bus_message *m, const char
         if (bus->nodes_modified)
                 return 0;
 
-        prefix = alloca(strlen(path) + 1);
+        pl = strlen(path);
+        assert(pl <= BUS_PATH_SIZE_MAX);
+        prefix = new(char, pl + 1);
+        if (!prefix)
+                return -ENOMEM;
+
         OBJECT_PATH_FOREACH_PREFIX(prefix, path) {
                 r = object_removed_append_all_prefix(bus, m, s, prefix, path, true);
                 if (r < 0)
@@ -2619,7 +2653,8 @@ static int interfaces_added_append_one(
                 const char *path,
                 const char *interface) {
 
-        char *prefix;
+        _cleanup_free_ char *prefix = NULL;
+        size_t pl;
         int r;
 
         assert(bus);
@@ -2633,7 +2668,12 @@ static int interfaces_added_append_one(
         if (bus->nodes_modified)
                 return 0;
 
-        prefix = alloca(strlen(path) + 1);
+        pl = strlen(path);
+        assert(pl <= BUS_PATH_SIZE_MAX);
+        prefix = new(char, pl + 1);
+        if (!prefix)
+                return -ENOMEM;
+
         OBJECT_PATH_FOREACH_PREFIX(prefix, path) {
                 r = interfaces_added_append_one_prefix(bus, m, prefix, path, interface, true);
                 if (r != 0)