[OpenJDK 2D-Dev] RFR: 8262829: Native crash in Win32PrintServiceLookup.getAllPrinterNames()
psadhukhan at openjdk.java.net
Fri Mar 5 11:22:41 UTC 2021
On Thu, 4 Mar 2021 21:37:33 GMT, Alexey Ivanov <aivanov at openjdk.org> wrote:
> **Root cause:**
> `getPrinterNames()` has two calls to [`::EnumPrinters`](https://docs.microsoft.com/en-us/windows/win32/printdocs/enumprinters). The first call is to get the required buffer size to contain the structures and any strings. The second call is to get the list of printers.
> Yet the list of printers or the names of printers can change between the two calls. If it happens, the second call to `EnumPrinters` fails but it is not checked.
> I couldn't reproduce the crash myself. However, I reproduced the failure in the second call to `::EnumPrinters` by adding `::Sleep(500)` and by renaming the printers so that the data doesn't fit into the allocated buffer:
> 1: bResult: 0, cbNeeded: 504, cReturned: 0
> 2: bResult: 0, cbNeeded: 512, cReturned: 0
> !!! error
> During my testing, `cReturned` has always been zero whenever `EnumPrinters` fails.
> The crash dumps show that `cReturned` is non-zero but the `pPrinterEnum` buffer doesn't contain valid data. Reading `info4->pPrinterName` at the line
> utf_str = JNU_NewStringPlatform(env, info4->pPrinterName);
> raises Access Violation exception.
> **The fix:**
> Check the return value of `EnumPrinters` and allow for 5 retries. If the function still returns failure, make sure `cReturned` is set to zero.
> I'm going to close [JDK-6996051](https://bugs.openjdk.java.net/browse/JDK-6996051) and [JDK-8182683](https://bugs.openjdk.java.net/browse/JDK-8182683) reported previously about the same crash as duplicate of the current [JDK-8262829](https://bugs.openjdk.java.net/browse/JDK-8262829).
> I used [`RemotePrinterStatusRefresh.java`](https://github.com/openjdk/jdk/blob/master/test/jdk/java/awt/print/RemotePrinterStatusRefresh/RemotePrinterStatusRefresh.java) for testing, it shows the list of currently available printers. In the background I ran `PrinterRename.ps1` PowerShell script which remains a printer, the script is attached to the JBS issue.
> Without the fix, the list of available printers was empty occasionally because `EnumPrinters` returned failure and set `cReturned` to zero. With the fix, the list of printers is always filled.
Marked as reviewed by psadhukhan (Reviewer).
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