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Fix crash when reading stats file at startup with fixed-sized kinds

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pgstat_read_statsfile() has never checked that the kind of a hash entry
is variable-sized.  Since 44539786b8, that has begun tracking which
hash table a kind ID should use, it is possible to finish with a NULL
pointer dereference for a PGSTAT_FILE_ENTRY_HASH.  Fixed-sized stats
kinds have no hash table and no DSA area, hence their dsa references in
pgStatLocal.kind_hash[] are NULL.

This case can occur when reading statistics files if the same kind ID is
reused across server restarts, with shared_preload_libraries loading
different stats kind information each time: stats written with a set of
PGSTAT_FILE_ENTRY_HASH, then read back with the same kind ID pointing to
a custom fixed-sized kind info.

Oversight in 44539786b8.

Reported-by: Zsolt Parragi <zsolt.parragi@percona.com>
Author: Sami Imseih <samimseih.pg@gmail.com>
Author: Zsolt Parragi <zsolt.parragi@percona.com>
Discussion: https://postgr.es/m/CAN4CZFMxuOOuYV14+i3YcPG-16q02eBtSVa82J111=ZnDwSicA@mail.gmail.com
This commit is contained in:
Michael Paquier
2026-10-15 08:23:09 +09:00
parent aadce2c10f
commit 0d110901f0
1 changed files with 8 additions and 0 deletions
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8
src/backend/utils/activity/pgstat.c
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@@ -2048,6 +2048,14 @@ pgstat_read_statsfile(void)
key.objid, t);
goto error;
}
if (kind_info->fixed_amount)
{
elog(WARNING, "invalid fixed_amount in stats kind for entry %u/%u/%" PRIu64 " of type %c",
key.kind, key.dboid,
key.objid, t);
goto error;
}
}
else
{