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Bug 1432409 part 1 - Prevent nsDeviceContextSpecProxy using RemotePrintJobChild if initialization fails. r=dholbert

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When RemotePrintJobChild::InitializePrint sends a message to the parent
process to ask it to initialize printing it spins the event loop and
waits for a reply.  If the parent fails to initialize printing it will
send back an error message followed immediately by a second message
telling the child process to delete its RemotePrintJobChild.  The error
message causes the nested event loop to terminate and blocks
RemotePrintJobChild::InitializePrint.  We then do various async things
to clean up, some of which can try to post messages to the parent
process's RemotePrintJobParent.  This is a problem since the delete
message is pending in the child process's event loop resulting in a
race between the code that wants to use the RemotePrintJobChild to send
a message to the parent process, and the delete event that will make us
crash if anyone tries to use the RemotePrintJobChild.

This patch makes sure that if nsDeviceContextSpecProxy's BeginDocument
returns failure (remote print job initialization failed) that its
EndDocument and AbortDocument methods are then no-ops and will not try
to use its RemotePrintJobChild.  (BeginPage and EndPage are not changed
since they are not called if BeginDocument returns an error result.)

MozReview-Commit-ID: 2H6GHjngX7R
This commit is contained in:
Jonathan Watt 2018-02-16 14:53:26 +00:00
parent be9a2c904e
commit f6cb92ef33
1 changed files with 17 additions and 5 deletions
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22
widget/nsDeviceContextSpecProxy.cpp
View File

@ -139,22 +139,34 @@ nsDeviceContextSpecProxy::BeginDocument(const nsAString& aTitle,
int32_t aStartPage, int32_t aEndPage)
{
mRecorder = new mozilla::layout::DrawEventRecorderPRFileDesc();
return mRemotePrintJob->InitializePrint(nsString(aTitle),
nsString(aPrintToFileName),
aStartPage, aEndPage);
nsresult rv = mRemotePrintJob->InitializePrint(nsString(aTitle),
nsString(aPrintToFileName),
aStartPage, aEndPage);
if (NS_FAILED(rv)) {
// The parent process will send a 'delete' message to tell this process to
// delete our RemotePrintJobChild. As soon as we return to the event loop
// and evaluate that message we will crash if we try to access
// mRemotePrintJob. We must not try to use it again.
mRemotePrintJob = nullptr;
}
return rv;
}
NS_IMETHODIMP
nsDeviceContextSpecProxy::EndDocument()
{
Unused << mRemotePrintJob->SendFinalizePrint();
if (mRemotePrintJob) {
Unused << mRemotePrintJob->SendFinalizePrint();
}
return NS_OK;
}
NS_IMETHODIMP
nsDeviceContextSpecProxy::AbortDocument()
{
Unused << mRemotePrintJob->SendAbortPrint(NS_OK);
if (mRemotePrintJob) {
Unused << mRemotePrintJob->SendAbortPrint(NS_OK);
}
return NS_OK;
}