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Commit8481f99

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Check for relation length overrun soon enough.
We don't allow relations to exceed 2^32-1 blocks, because blocknumbers are 32 bits and the last possible block number is reservedto mean InvalidBlockNumber. There is a check for this in mdextend,but that's really way too late, because the smgr API requires us tocreate a buffer for the block-to-be-added, and we do not want tohave any buffer with blocknum InvalidBlockNumber. (Such a casecan trigger assertions in bufmgr.c, plus I think it might confuseReadBuffer's logic for data-past-EOF later on.) So put the checkinto ReadBuffer.Per report from Christoph Berg. It's been like this forever,so back-patch to all supported branches.Discussion:https://postgr.es/m/YTn1iTkUYBZfcODk@msg.credativ.de
1 parent596ba75 commit8481f99

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2 files changed

+11
-1
lines changed

2 files changed

+11
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lines changed

‎src/backend/storage/buffer/bufmgr.c

Lines changed: 9 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -824,7 +824,16 @@ ReadBuffer_common(SMgrRelation smgr, char relpersistence, ForkNumber forkNum,
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/* Substitute proper block number if caller asked for P_NEW */
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if (isExtend)
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{
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blockNum=smgrnblocks(smgr,forkNum);
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/* Fail if relation is already at maximum possible length */
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if (blockNum==P_NEW)
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ereport(ERROR,
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(errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED),
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errmsg("cannot extend relation %s beyond %u blocks",
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relpath(smgr->smgr_rnode,forkNum),
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P_NEW)));
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}
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if (isLocalBuf)
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{

‎src/backend/storage/smgr/md.c

Lines changed: 2 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -426,7 +426,8 @@ mdextend(SMgrRelation reln, ForkNumber forknum, BlockNumber blocknum,
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/*
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* If a relation manages to grow to 2^32-1 blocks, refuse to extend it any
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* more --- we mustn't create a block whose number actually is
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* InvalidBlockNumber.
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* InvalidBlockNumber. (Note that this failure should be unreachable
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* because of upstream checks in bufmgr.c.)
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*/
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if (blocknum==InvalidBlockNumber)
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ereport(ERROR,

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