service_manager: reorder permission checks for find
Reorder the find permission checks. This avoids generating misleading
SELinux denials when a service doesn't exist, or when a service is
prohibited to isolated apps.
The original reason for structuring the code this way is explained
in https://android-review.googlesource.com/#/c/100530/4/cmds/servicemanager/service_manager.c@172
The concern at the time was to avoid leaking a situation where
a caller could probe for the existance of a service. This turns out
to be unnecessary. The same return value is used for both a
permission denied and a service not found. The only side effect
is the generation of an SELinux audit log, which likely won't be
accessible to the calling application.
Change-Id: I9760e1821ed16102fa5f9bec07f8c34944565be9
diff --git a/cmds/servicemanager/service_manager.c b/cmds/servicemanager/service_manager.c
index f37427a..df46a60 100644
--- a/cmds/servicemanager/service_manager.c
+++ b/cmds/servicemanager/service_manager.c
@@ -169,28 +169,26 @@
uint32_t do_find_service(struct binder_state *bs, const uint16_t *s, size_t len, uid_t uid, pid_t spid)
{
- struct svcinfo *si;
+ struct svcinfo *si = find_svc(s, len);
+
+ if (!si || !si->handle) {
+ return 0;
+ }
+
+ if (!si->allow_isolated) {
+ // If this service doesn't allow access from isolated processes,
+ // then check the uid to see if it is isolated.
+ uid_t appid = uid % AID_USER;
+ if (appid >= AID_ISOLATED_START && appid <= AID_ISOLATED_END) {
+ return 0;
+ }
+ }
if (!svc_can_find(s, len, spid)) {
- ALOGE("find_service('%s') uid=%d - PERMISSION DENIED\n",
- str8(s, len), uid);
return 0;
}
- si = find_svc(s, len);
- //ALOGI("check_service('%s') handle = %x\n", str8(s, len), si ? si->handle : 0);
- if (si && si->handle) {
- if (!si->allow_isolated) {
- // If this service doesn't allow access from isolated processes,
- // then check the uid to see if it is isolated.
- uid_t appid = uid % AID_USER;
- if (appid >= AID_ISOLATED_START && appid <= AID_ISOLATED_END) {
- return 0;
- }
- }
- return si->handle;
- } else {
- return 0;
- }
+
+ return si->handle;
}
int do_add_service(struct binder_state *bs,