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Fix memory lifetime issues of replication slot stats.

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When accessing replication slot stats, introduced in 9868167500,
pgstat_read_statsfiles() reads the data into newly allocated
memory. Unfortunately the current memory context at that point is the
callers, leading to leaks and use-after-free dangers.

The fix is trivial, explicitly use pgStatLocalContext. There's some
potential for further improvements, but that's outside of the scope of
this bugfix.

No backpatch necessary, feature is only in HEAD.

Author: Andres Freund <andres@anarazel.de>
Discussion: https://postgr.es/m/20210317230447.c7uc4g3vbs4wi32i@alap3.anarazel.de
This commit is contained in:
Andres Freund
2021-03-17 16:18:37 -07:00
parent 70945649d7
commit 5f79580ad6
3 changed files with 28 additions and 1 deletions
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6
src/backend/postmaster/pgstat.c
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@ -5568,7 +5568,9 @@ pgstat_read_statsfiles(Oid onlydb, bool permanent, bool deep)
HASH_ELEM | HASH_BLOBS | HASH_CONTEXT);
/* Allocate the space for replication slot statistics */
replSlotStats = palloc0(max_replication_slots * sizeof(PgStat_ReplSlotStats));
replSlotStats = MemoryContextAllocZero(pgStatLocalContext,
max_replication_slots
* sizeof(PgStat_ReplSlotStats));
nReplSlotStats = 0;
/*
@ -6323,6 +6325,8 @@ pgstat_clear_snapshot(void)
pgStatDBHash = NULL;
localBackendStatusTable = NULL;
localNumBackends = 0;
replSlotStats = NULL;
nReplSlotStats = 0;
}