On Tue, 24 Mar 2026 14:44:53 GMT, Thomas Stuefe <[email protected]> wrote:
>>> > Do you have any more information on this security bug? >>> >>> I found following bug from mail thread. But I cannot access it due to >>> security bug. >>> >>> https://mail.openjdk.org/pipermail/hotspot-runtime-dev/2011-August/002357.html >>> >>> 4852809: Linux: do not use alternate signal stack >> >> Actually I made this public last year: >> https://bugs.openjdk.org/browse/JDK-4852809 >> >> There were two main issues: >> 1. Newly created threads inheriting the same alt-stack as parent >> 2. Issues with accessing TLS with Linux fixed-stack implementation >> >> I don't quite see how #1 could arise, and #2 is definitely not an issue any >> more. > > Hi @dholmes-ora and @YaSuenag ! > > Sorry for the rebase; something messed up my branch and I had to rebase over > master to get it clean again. Not sure what happened. > > Thank you both for your feedback; I was busy with other stuff, and this moved > down the pile. I tried to address your concerns. hotspot Tier1 and Tier2 are > currently running on my machine with the feature enabled. > > @dholmes-ora >> My main concern with this is that it is so hard to test and we will never >> know to what extent it is getting used. It's usefulness depends entirely on >> support organizations knowing about it and telling customers to enable this >> (in production - which they might balk at) to try and better diagnose >> mystery crashes. > > That is true, unfortunately. Whether this is useful enough is a matter of > taste, but I know I could have used it a bunch of times already, and there > are an unknown number of JVM-just-vanishes cases that could turn out to be > stack overflows. @tstuefe this still fails to build on Windows: c:\sb\prod\1774838743\workspace\open\src\hotspot\os\windows\threadAltSigStack_windows.cpp(29): error C2511: 'bool Thread::is_in_alternate_stack(address)': overloaded member function not found in 'Thread' and I see numerous crashes during testing with UseAltSignalStack true: # Internal Error (/opt/mach5/mesos/work_dir/slaves/34097d45-6766-47fe-90ff-77a661dffa48-S4094/frameworks/1735e8a2-a1db-478c-8104-60c8b0af87dd-0196/executors/1c6f5040-e8e1-4278-b164-fd150c0011f2/runs/93045c99-c0c0-4705-b75f-67953591fcc6/workspace/open/src/hotspot/share/runtime/thread.hpp:469), pid=213773, tid=213797 # assert(stack_base() > limit && limit >= stack_end()) failed: limit is outside of stack # # JRE version: Java(TM) SE Runtime Environment (27.0) (fastdebug build 27-internal-2026-03-30-0241507.david.holmes.jdk-dev2.git) # Java VM: Java HotSpot(TM) 64-Bit Server VM (fastdebug 27-internal-2026-03-30-0241507.david.holmes.jdk-dev2.git, mixed mode, sharing, tiered, compressed oops, compressed class ptrs, g1 gc, linux-amd64) # Problematic frame: # V [libjvm.so+0x1c1f251] UnhandledOops::register_unhandled_oop(oop*)+0x161 and SA core tests are failing e.g. Error occurred during stack walking: sun.jvm.hotspot.debugger.DebuggerException: get_thread_regs failed for a lwp at jdk.hotspot.agent/sun.jvm.hotspot.debugger.bsd.BsdDebuggerLocal.getThreadIntegerRegisterSet0(Native Method) at jdk.hotspot.agent/sun.jvm.hotspot.debugger.bsd.BsdDebuggerLocal.getThreadIntegerRegisterSet(BsdDebuggerLocal.java:472) at jdk.hotspot.agent/sun.jvm.hotspot.debugger.bsd.BsdThread.getContext(BsdThread.java:68) at jdk.hotspot.agent/sun.jvm.hotspot.runtime.bsd_amd64.BsdAMD64JavaThreadPDAccess.getCurrentFrameGuess(BsdAMD64JavaThreadPDAccess.java:98) at jdk.hotspot.agent/sun.jvm.hotspot.runtime.JavaThread.getCurrentFrameGuess(JavaThread.java:266) at jdk.hotspot.agent/sun.jvm.hotspot.runtime.JavaThread.getLastJavaVFrameDbg(JavaThread.java:228) at jdk.hotspot.agent/sun.jvm.hotspot.tools.StackTrace.run(StackTrace.java:81) at jdk.hotspot.agent/sun.jvm.hotspot.CommandProcessor$22.doit(CommandProcessor.java:983) at jdk.hotspot.agent/sun.jvm.hotspot.CommandProcessor.executeCommand(CommandProcessor.java:2051) at jdk.hotspot.agent/sun.jvm.hotspot.CommandProcessor.executeCommand(CommandProcessor.java:2021) at jdk.hotspot.agent/sun.jvm.hotspot.CommandProcessor.run(CommandProcessor.java:1892) at jdk.hotspot.agent/sun.jvm.hotspot.CLHSDB.run(CLHSDB.java:113) at jdk.hotspot.agent/sun.jvm.hotspot.CLHSDB.main(CLHSDB.java:45) at jdk.hotspot.agent/sun.jvm.hotspot.SALauncher.runCLHSDB(SALauncher.java:285) at jdk.hotspot.agent/sun.jvm.hotspot.SALauncher.main(SALauncher.java:507) ------------- PR Comment: https://git.openjdk.org/jdk/pull/29559#issuecomment-4152072685
