Re: Invalid memory access in pg_stat_get_subscription

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Kuntal Ghosh <kuntalghosh(dot)2007(at)gmail(dot)com>
Cc: PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Invalid memory access in pg_stat_get_subscription
Date: 2022-06-07 19:14:43
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Kuntal Ghosh <kuntalghosh(dot)2007(at)gmail(dot)com> writes:
> While exploring some code in logical replication worker
> implementation, I noticed that we're accessing an invalid memory while
> traversing LogicalRepCtx->workers[i].
> For the above structure, we're allocating
> max_logical_replication_workers times LogicalRepWorker amount of
> memory in ApplyLauncherShmemSize. But, in the for loop, we're
> accessing the max_logical_replication_workers + 1 location which is
> resulting in random crashes.

I concur that that's a bug, but eyeing the code, it seems like an
actual crash would be improbable. Have you seen one? Can you
reproduce it?

> Please find the patch that fixes the issue. I'm not sure whether we
> should add a regression test for the same.

How would you make a stable regression test for that?

regards, tom lane

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