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| author | Robert Haas <rhaas@postgresql.org> | 2022-08-12 08:25:41 -0400 |
|---|---|---|
| committer | Robert Haas <rhaas@postgresql.org> | 2022-08-12 08:25:41 -0400 |
| commit | 76733b399c490885564a560718de23d98bb5e66d (patch) | |
| tree | 45f1fcf1650e4b4b02af7b0d062f10d2232d4eef /src/backend/commands/dbcommands.c | |
| parent | 3d895bc846f25859bd6dd242fbf204e6c5166e6f (diff) | |
| download | postgresql-76733b399c490885564a560718de23d98bb5e66d.tar.gz postgresql-76733b399c490885564a560718de23d98bb5e66d.zip | |
Avoid using a fake relcache entry to own an SmgrRelation.
If an error occurs before we close the fake relcache entry, the the
fake relcache entry will be destroyed by the SmgrRelation will
survive until end of transaction. Its smgr_owner pointer ends up
pointing to already-freed memory.
The original reason for using a fake relcache entry here was to try
to avoid reusing an SMgrRelation across a relevant invalidation. To
avoid that problem, just call smgropen() again each time we need a
reference to it. Hopefully someday we will come up with a more
elegant approach, but accessing uninitialized memory is bad so let's
do this for now.
Dilip Kumar, reviewed by Andres Freund and Tom Lane. Report by
Justin Pryzby.
Discussion: http://postgr.es/m/20220802175043.GA13682@telsasoft.com
Discussion: http://postgr.es/m/CAFiTN-vSFeE6_W9z698XNtFROOA_nSqUXWqLcG0emob_kJ+dEQ@mail.gmail.com
Diffstat (limited to 'src/backend/commands/dbcommands.c')
| -rw-r--r-- | src/backend/commands/dbcommands.c | 15 |
1 files changed, 4 insertions, 11 deletions
diff --git a/src/backend/commands/dbcommands.c b/src/backend/commands/dbcommands.c index 9f990a8d68f..b31a30550b0 100644 --- a/src/backend/commands/dbcommands.c +++ b/src/backend/commands/dbcommands.c @@ -258,8 +258,8 @@ ScanSourceDatabasePgClass(Oid tbid, Oid dbid, char *srcpath) Page page; List *rlocatorlist = NIL; LockRelId relid; - Relation rel; Snapshot snapshot; + SMgrRelation smgr; BufferAccessStrategy bstrategy; /* Get pg_class relfilenumber. */ @@ -276,16 +276,9 @@ ScanSourceDatabasePgClass(Oid tbid, Oid dbid, char *srcpath) rlocator.dbOid = dbid; rlocator.relNumber = relfilenumber; - /* - * We can't use a real relcache entry for a relation in some other - * database, but since we're only going to access the fields related to - * physical storage, a fake one is good enough. If we didn't do this and - * used the smgr layer directly, we would have to worry about - * invalidations. - */ - rel = CreateFakeRelcacheEntry(rlocator); - nblocks = smgrnblocks(RelationGetSmgr(rel), MAIN_FORKNUM); - FreeFakeRelcacheEntry(rel); + smgr = smgropen(rlocator, InvalidBackendId); + nblocks = smgrnblocks(smgr, MAIN_FORKNUM); + smgrclose(smgr); /* Use a buffer access strategy since this is a bulk read operation. */ bstrategy = GetAccessStrategy(BAS_BULKREAD); |