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Ensure that ScanInfo is cached before callbacks fire

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Fixes a regression that was introduced in aosp/1312940.

There is a critical section in requestNetworkScan after the scanId
has been generated and before the ScanInfo is added to the cache.
If during this time a callback fires on a separate thread, it will
not yet find the ScanInfo record, and due to strict checking, this
causes a RuntimeException. This CL re-expands the synchronized block
to cover the critical section, and clarifies a little bounds checking.

Note: this change is not ideal. This means that all callbacks for all
scans will be blocked while a request for a new scan is being made,
which was the motivation behind the change that introduced this
regression. But, a narrow performance hit is better than a crash, and
it's not worth the complexity of a bigger fix.

Bug: 200634560
Test: compilation
Merged-In: I4670da109256170121ceb6d8fbad0efda310335f
Change-Id: I4670da109256170121ceb6d8fbad0efda310335f
This commit is contained in:
Nathan Harold
2021-10-20 12:42:27 -07:00
parent bb9ecdd2af
commit f183b69cf5
1 changed files with 18 additions and 17 deletions
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35
telephony/java/android/telephony/TelephonyScanManager.java
View File

@@ -36,6 +36,7 @@ import com.android.telephony.Rlog;
import java.util.Arrays;
import java.util.List;
import java.util.Objects;
import java.util.concurrent.Executor;
/**
@@ -152,16 +153,9 @@ public final class TelephonyScanManager {
throw new RuntimeException(
"Failed to find NetworkScanInfo with id " + message.arg2);
}
NetworkScanCallback callback = nsi.mCallback;
Executor executor = nsi.mExecutor;
if (callback == null) {
throw new RuntimeException(
"Failed to find NetworkScanCallback with id " + message.arg2);
}
if (executor == null) {
throw new RuntimeException(
"Failed to find Executor with id " + message.arg2);
}
final NetworkScanCallback callback = nsi.mCallback;
final Executor executor = nsi.mExecutor;
switch (message.what) {
case CALLBACK_RESTRICTED_SCAN_RESULTS:
@@ -246,17 +240,24 @@ public final class TelephonyScanManager {
NetworkScanRequest request, Executor executor, NetworkScanCallback callback,
String callingPackage, @Nullable String callingFeatureId) {
try {
Objects.requireNonNull(request, "Request was null");
Objects.requireNonNull(callback, "Callback was null");
Objects.requireNonNull(executor, "Executor was null");
final ITelephony telephony = getITelephony();
if (telephony == null) return null;
int scanId = telephony.requestNetworkScan(
subId, request, mMessenger, new Binder(), callingPackage,
callingFeatureId);
if (scanId == INVALID_SCAN_ID) {
Rlog.e(TAG, "Failed to initiate network scan");
return null;
}
// The lock must be taken before calling requestNetworkScan because the resulting
// scanId can be invoked asynchronously on another thread at any time after
// requestNetworkScan invoked, leaving a critical section between that call and adding
// the record to the ScanInfo cache.
synchronized (mScanInfo) {
int scanId = telephony.requestNetworkScan(
subId, request, mMessenger, new Binder(), callingPackage,
callingFeatureId);
if (scanId == INVALID_SCAN_ID) {
Rlog.e(TAG, "Failed to initiate network scan");
return null;
}
// We link to death whenever a scan is started to ensure that we are linked
// at the point that phone process death might matter.
// We never unlink because: