RFR: 8333149: ubsan : memset on nullptr target detected in jvmtiEnvBase.cpp get_object_monitor_usage

[David Holmes]

On Wed, 29 May 2024 12:38:21 GMT, Matthias Baesken <mbaesken at openjdk.org> wrote:

>> When running with ubsan - enabled binaries (--enable-ubsan),
>> in the vmTestbase/nsk/jdi tests some cases of memset on nullptr destinations are detected in get_object_monitor_usage .
>> 
>> // null out memory for robustness
>> memset(ret.waiters, 0, ret.waiter_count * sizeof(jthread *));
>> memset(ret.notify_waiters, 0, ret.notify_waiter_count * sizeof(jthread *));
>> 
>> probably we should add checks there.
>> Example :
>> vmTestbase/nsk/jdi/ObjectReference/entryCount/entrycount002/TestDescription.jtr
>> 
>> debugee.stderr> /src/hotspot/share/prims/jvmtiEnvBase.cpp:1560:11: runtime error: null pointer passed as argument 1, which is declared to never be null
>> debugee.stderr> #0 0x7ffb2568559c in JvmtiEnvBase::get_object_monitor_usage(JavaThread*, _jobject*, jvmtiMonitorUsage*) src/hotspot/share/prims/jvmtiEnvBase.cpp:1560
>> debugee.stderr> #1 0x7ffb27987bd7 in VM_GetObjectMonitorUsage::doit() src/hotspot/share/prims/jvmtiEnvBase.hpp:594
>> debugee.stderr> #2 0x7ffb28ddc2dd in VM_Operation::evaluate() src/hotspot/share/runtime/vmOperations.cpp:75
>> debugee.stderr> #3 0x7ffb28deac41 in VMThread::evaluate_operation(VM_Operation*) src/hotspot/share/runtime/vmThread.cpp:283
>> debugee.stderr> #4 0x7ffb28decc4f in VMThread::inner_execute(VM_Operation*) src/hotspot/share/runtime/vmThread.cpp:427
>> debugee.stderr> #5 0x7ffb28ded7b9 in VMThread::loop() src/hotspot/share/runtime/vmThread.cpp:493
>> debugee.stderr> #6 0x7ffb28ded8a7 in VMThread::run() src/hotspot/share/runtime/vmThread.cpp:177
>> debugee.stderr> #7 0x7ffb28b7e31a in Thread::call_run() src/hotspot/share/runtime/thread.cpp:225
>> debugee.stderr> #8 0x7ffb281c4971 in thread_native_entry src/hotspot/os/linux/os_linux.cpp:846
>> debugee.stderr> #9 0x7ffb2df416e9 in start_thread (/lib64/libpthread.so.0+0xa6e9) (BuildId: 2f8d3c2d0f4d7888c2598d2ff6356537f5708a73)
>> debugee.stderr> #10 0x7ffb2d51550e in clone (/lib64/libc.so.6+0x11850e) (BuildId: f732026552f6adff988b338e92d466bc81a01c37)
>> 
>> vmTestbase/nsk/jdi/ObjectReference/owningThread/owningthread002/TestDescription.jtr
>> 
>> debugee.stderr> /src/hotspot/share/prims/jvmtiEnvBase.cpp:1561:11: runtime error: null pointer passed as argument 1, which is declared to never be null
>> debugee.stderr> #0 0x7f1e070855bb in JvmtiEnvBase::get_object_monitor_usage(JavaThread*, _jobject*, jvmtiMonitorUsage*) src/hotspot/share/prims/jvmtiEnvBase.cpp:1561
>> debugee.stderr> #1 0x7f1e09387bd7 in VM_GetObjectMonitorUsage::doit() src/hotspot/share/prims/jvmtiEnvBase.hpp:594
>> debugee.std...
>
> Hi Martin and Serguei, thanks for the reviews !

@MBaesken  This was not proposed as a trivial PR and so is subject to the 24 hour rule. Please don't push these ubsan "fixes" quickly as we need time to assess their validity and the right way to address them.

This fix looks wrong to me because those values cannot be null as it implies the `allocate` function failed which means we would not reach this code!

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PR Comment: https://git.openjdk.org/jdk/pull/19450#issuecomment-2138540409