On Thu, 4 Mar 2021 21:37:33 GMT, Alexey Ivanov <aiva...@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). > > **Testing:** > 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. This pull request has now been integrated. Changeset: a6e34b3d Author: Alexey Ivanov <aiva...@openjdk.org> URL: https://git.openjdk.java.net/jdk/commit/a6e34b3d Stats: 20 lines in 1 file changed: 13 ins; 0 del; 7 mod 8262829: Native crash in Win32PrintServiceLookup.getAllPrinterNames() Reviewed-by: prr, psadhukhan, serb ------------- PR: https://git.openjdk.java.net/jdk/pull/2836
