On Fri, 5 Mar 2021 01:27:47 GMT, Sergey Bylokhov <s...@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. > > src/java.desktop/windows/native/libawt/windows/WPrinterJob.cpp line 136: > >> 134: >> 135: try { >> 136: ::EnumPrinters(flags, NULL, 4, NULL, > > Don't we need to check that this method call succeeds? Probably it is a crash > reason when the EnumPrinters fails but we use cbNeeded anyway for array > allocation? I guess since we are changing this method anyway, can we use PRINTER_ENUM_CONNECTIONS flag instead of hardcoded 4 so that it is more informative!! ------------- PR: https://git.openjdk.java.net/jdk/pull/2836
