Bug: MemorySegment bounds check doesn't work for some values and allows segmentation fault

[Maurizio Cimadamore]

Hi,
thanks for the report - I suspect this is caused by the long vs. int 
workaround we have scattered all over the place.

Can you try running with "-Djdk.incubator.foreign.SmallSegments=false" 
and see what happens?

Cheers
Maurizio

On 30/04/2021 12:45, Marcel Käufler wrote:
> Hi,
>
> I've encountered a bug with the MemorySegment bounds check. For some 
> values, instead of throwing and IndexOutOfBoundsException, the access 
> goes through and causes a segmentation fault. I didn't dig into it but 
> I expect some kind of overflow / casting error that makes the address 
> appear to be in a valid range.
>
> Tested with both the JDK 16 release and the current panama main branch.
>
> To reproduce:
>
> import jdk.incubator.foreign.MemoryAccess;
> import jdk.incubator.foreign.MemorySegment;
> import jdk.incubator.foreign.ResourceScope;
>
> public class SIGSEGV {
>     public static void main(String[] args) {
>         MemorySegment memorySegment = 
> MemorySegment.allocateNative(2147479552, ResourceScope.globalScope());
>         MemoryAccess.getLongAtOffset(memorySegment, 
> 8223372036854705800L);
>     }
> }
>
>
>
> #
> # A fatal error has been detected by the Java Runtime Environment:
> #
> #  SIGSEGV (0xb) at pc=0x00007f345fc19053, pid=224993, tid=224996
> #
> # JRE version: OpenJDK Runtime Environment (17.0) (build 
> 17-internal+0-adhoc..panama-foreign)
> # Java VM: OpenJDK 64-Bit Server VM 
> (17-internal+0-adhoc..panama-foreign, mixed mode, sharing, tiered, 
> compressed oops, compressed class ptrs, g1 gc, linux-amd64)
> # Problematic frame:
> # V  [libjvm.so+0xf0a053]  Unsafe_GetLong+0x133
> #
> # Core dump will be written. Default location: Core dumps may be 
> processed with "/usr/lib/systemd/systemd-coredump %P %u %g %s %t %c 
> %h" (or dumping to /home/marcel/IdeaProjects/BoundsCheck/core.224993)
> #
> # An error report file with more information is saved as:
> # /home/marcel/IdeaProjects/BoundsCheck/hs_err_pid224993.log
> #
> # If you would like to submit a bug report, please visit:
> #   https://bugreport.java.com/bugreport/crash.jsp
> #
>
> Process finished with exit code 134 (interrupted by signal 6: SIGABRT)
>
>
> Best Regards,
> Marcel
>