[jdk17u-dev] RFR: 8332825: ubsan: guardedMemory.cpp:35:11: runtime error: null pointer passed as argument 2, which is declared to never be null

[Thomas Stuefe]

On Thu, 12 Sep 2024 09:09:57 GMT, Goetz Lindenmaier <goetz at openjdk.org> wrote:

>> src/hotspot/share/memory/guardedMemory.cpp line 38:
>> 
>>> 36:     if (ptr != nullptr) {
>>> 37:       memcpy(innerp, ptr, len);
>>> 38:     }
>> 
>> Hmm. innerp can never be null. If anything, we should assert.
>
> Hi,
> I don't understand. First, innerp is not checked for null. Second: does the code in 17 differ to 21&head? Else we should change this to an assertion in head, first.

Hi Goetz!

`innerp` is the result of 


  u_char* get_user_ptr() const {
    assert(_base_addr != nullptr, "Not wrapping any memory");
    return _base_addr + sizeof(GuardHeader);
  }


which cannot return null. _base_addr is the result of a malloc and we only ever enter this path if that malloc succeeded. It is also asserted at least twice.

Cheers, Thomas

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PR Review Comment: https://git.openjdk.org/jdk17u-dev/pull/2829#discussion_r1756499855