Re: BUG #17798: Incorrect memory access occurs when using BEFORE ROW UPDATE trigger

On Sun, Apr 30, 2023 at 5:00 AM Alexander Lakhin <exclusion@gmail.com> wrote:
> Yeah, also the environment changed since 86dc90056, so I couldn't just revert
> that commit to test the ExecFilterJunk() behavior on master.
>
> All the questions you raised require a more thorough investigation.

Are you aware of the fact that Valgrind has custom instrumentation
that makes it directly capable of detecting access to no-longer-pinned
buffers? See commits 7b7ed046 and 1e0dfd16.

I think that that may be a factor here. If it is, then it's a little
surprising that you ever found the problem with ASAN, since of course
we don't have custom ASAN instrumentation that tells ASAN things like
"until I say otherwise, it is not okay to read from this range of
memory, which is this backend's memory mapping for an individual
shared buffer that was just unpinned".

--
Peter Geoghegan