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Fix the race condition between creating and killing process group

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Framework takes care of the process group creation for the processes
forked by webview and app zygote. There is a small window
between the fork and the process group creation, if the process is
deemed to be killed during that window, the process group creation
would fail and crash the system. Now add a lock around that.

Bug: 270103958
Test: Manual
Change-Id: Id602d9cd5243b7726d88e2fa40fd3d3431086a64
This commit is contained in:
Jing Ji
2023-05-02 10:26:48 -07:00
parent d06a6b54c2
commit f151a15ce9
2 changed files with 50 additions and 10 deletions
Download Patch File Download Diff File Expand all files Collapse all files

28
services/core/java/com/android/server/am/ProcessList.java
View File

@@ -2300,6 +2300,8 @@ public final class ProcessList {
final Process.ProcessStartResult startResult;
boolean regularZygote = false;
app.mProcessGroupCreated = false;
app.mSkipProcessGroupCreation = false;
if (hostingRecord.usesWebviewZygote()) {
startResult = startWebView(entryPoint,
app.processName, uid, uid, gids, runtimeFlags, mountExternal,
@@ -2328,18 +2330,28 @@ public final class ProcessList {
isTopApp, app.getDisabledCompatChanges(), pkgDataInfoMap,
allowlistedAppDataInfoMap, bindMountAppsData, bindMountAppStorageDirs,
new String[]{PROC_START_SEQ_IDENT + app.getStartSeq()});
// By now the process group should have been created by zygote.
app.mProcessGroupCreated = true;
}
if (!regularZygote) {
// webview and app zygote don't have the permission to create the nodes
final int res = Process.createProcessGroup(uid, startResult.pid);
if (res < 0) {
if (res == -OsConstants.ESRCH) {
Slog.e(ActivityManagerService.TAG, "Unable to create process group for "
+ app.processName + " (" + startResult.pid + ")");
} else {
throw new AssertionError("Unable to create process group for "
+ app.processName + " (" + startResult.pid + ")");
synchronized (app) {
if (!app.mSkipProcessGroupCreation) {
// If we're not told to skip the process group creation, go create it.
final int res = Process.createProcessGroup(uid, startResult.pid);
if (res < 0) {
if (res == -OsConstants.ESRCH) {
Slog.e(ActivityManagerService.TAG,
"Unable to create process group for "
+ app.processName + " (" + startResult.pid + ")");
} else {
throw new AssertionError("Unable to create process group for "
+ app.processName + " (" + startResult.pid + ")");
}
} else {
app.mProcessGroupCreated = true;
}
}
}
}

32
services/core/java/com/android/server/am/ProcessRecord.java
View File

@@ -424,6 +424,16 @@ class ProcessRecord implements WindowProcessListener {
*/
Runnable mSuccessorStartRunnable;
/**
* Whether or not the process group of this process has been created.
*/
volatile boolean mProcessGroupCreated;
/**
* Whether or not we should skip the process group creation.
*/
volatile boolean mSkipProcessGroupCreation;
void setStartParams(int startUid, HostingRecord hostingRecord, String seInfo,
long startUptime, long startElapsedTime) {
this.mStartUid = startUid;
@@ -1192,8 +1202,26 @@ class ProcessRecord implements WindowProcessListener {
EventLog.writeEvent(EventLogTags.AM_KILL,
userId, mPid, processName, mState.getSetAdj(), reason);
Process.killProcessQuiet(mPid);
if (!asyncKPG) Process.sendSignalToProcessGroup(uid, mPid, OsConstants.SIGKILL);
ProcessList.killProcessGroup(uid, mPid);
final boolean killProcessGroup;
if (mHostingRecord != null
&& (mHostingRecord.usesWebviewZygote() || mHostingRecord.usesAppZygote())) {
synchronized (ProcessRecord.this) {
killProcessGroup = mProcessGroupCreated;
if (!killProcessGroup) {
// The process group hasn't been created, request to skip it.
mSkipProcessGroupCreation = true;
}
}
} else {
killProcessGroup = true;
}
if (killProcessGroup) {
if (asyncKPG) {
ProcessList.killProcessGroup(uid, mPid);
} else {
Process.sendSignalToProcessGroup(uid, mPid, OsConstants.SIGKILL);
}
}
} else {
mPendingStart = false;
}