Fix local pgstat entry leak on OOM during entry creation
When pgstat_init_entry() fails due to an OOM in the DSA allocation,
pgstat_get_entry_ref() cleaned up the shared hashtable but forgot to
remove the local reference that pgstat_get_entry_ref_cached() had
already inserted into pgStatEntryRefHash.
Missing this cleanup would leave a backend with a stale local cache
entry whose entry_ref points to a NULL shared_stats. If
pgstat_gc_entry_refs() runs with this reference still around, it would
crash due to a pointer dereference.
The local reference is now removed before removing the shared entry,
the order being sensitive to pending interrupts.
Oversight in 8191e0c16a03.
Author: Niall Newman <nn@turacolabs.com>
Discussion: https://postgr.es/m/2FDAA194-9CF3-4FD7-A450-F1A4BEB125F6@turacolabs.com
Backpatch-through: 15
Branch
------
REL_16_STABLE
Details
-------
https://git.postgresql.org/pg/commitdiff/636bcd6a56a84bec591961cbf1e773025607a4bf
Modified Files
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src/backend/utils/activity/pgstat_shmem.c | 7 +++++--
1 file changed, 5 insertions(+), 2 deletions(-)
