From: John Naylor <john.naylor@postgresql.org>
To: pgsql-committers@lists.postgresql.org
Subject: pgsql: Fix use-after-free in parallel_vacuum_reset_dead_items
Date: Wed, 04 Dec 2024 10:12:45 +0000
Message-ID: <E1tImNB-0012tF-9D@gemulon.postgresql.org> (raw)
Fix use-after-free in parallel_vacuum_reset_dead_items
parallel_vacuum_reset_dead_items used a local variable to hold a
pointer from the passed vacrel, purely as a shorthand. This pointer
was later freed and a new allocation was made and stored to the
struct. Then the local pointer was mistakenly referenced again.
This apparently happened not to break anything since the freed chunk
would have been put on the context's freelist, so it was accidentally
the same pointer anyway, in which case the DSA handle was correctly
updated. The minimal fix is to change two places so they access
dead_items through the vacrel. This coding style is a maintenance
hazard, so while at it get rid of most other similar usages, which
were inconsistently used anyway.
Analysis and patch by Vallimaharajan G, with further defensive coding
by me
Backpath to v17, when TidStore came in
Discussion: https://postgr.es/m/1936493cc38.68cb2ef27266.7456585136086197135@zohocorp.com
Branch
------
REL_17_STABLE
Details
-------
https://git.postgresql.org/pg/commitdiff/83ce20d67184d79f7a1e65feed7c06ec03e4472d
Modified Files
--------------
src/backend/access/heap/vacuumlazy.c | 17 ++++++-----------
src/backend/commands/vacuumparallel.c | 7 +++----
2 files changed, 9 insertions(+), 15 deletions(-)
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To: pgsql-committers@postgresql.org
Cc: john.naylor@postgresql.org, pgsql-committers@lists.postgresql.org
Subject: Re: pgsql: Fix use-after-free in parallel_vacuum_reset_dead_items
In-Reply-To: <E1tImNB-0012tF-9D@gemulon.postgresql.org>
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