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| author | Tom Lane <tgl@sss.pgh.pa.us> | 2021-09-09 11:45:48 -0400 |
|---|---|---|
| committer | Tom Lane <tgl@sss.pgh.pa.us> | 2021-09-09 11:45:48 -0400 |
| commit | 04118de78fe9a8a7160775b47e89bf21a5efb620 (patch) | |
| tree | 6c1687d517a23199e13563635cb66cf32b817dd3 | |
| parent | dd9b3fced83edb51a3e2f44d3d4476a45d0f5a24 (diff) | |
| download | postgresql-04118de78fe9a8a7160775b47e89bf21a5efb620.tar.gz postgresql-04118de78fe9a8a7160775b47e89bf21a5efb620.zip | |
Check for relation length overrun soon enough.
We don't allow relations to exceed 2^32-1 blocks, because block
numbers are 32 bits and the last possible block number is reserved
to mean InvalidBlockNumber. There is a check for this in mdextend,
but that's really way too late, because the smgr API requires us to
create a buffer for the block-to-be-added, and we do not want to
have any buffer with blocknum InvalidBlockNumber. (Such a case
can trigger assertions in bufmgr.c, plus I think it might confuse
ReadBuffer's logic for data-past-EOF later on.) So put the check
into 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
| -rw-r--r-- | src/backend/storage/buffer/bufmgr.c | 9 | ||||
| -rw-r--r-- | src/backend/storage/smgr/md.c | 3 |
2 files changed, 11 insertions, 1 deletions
diff --git a/src/backend/storage/buffer/bufmgr.c b/src/backend/storage/buffer/bufmgr.c index 9381f9981d3..597afedef70 100644 --- a/src/backend/storage/buffer/bufmgr.c +++ b/src/backend/storage/buffer/bufmgr.c @@ -739,7 +739,16 @@ ReadBuffer_common(SMgrRelation smgr, char relpersistence, ForkNumber forkNum, /* Substitute proper block number if caller asked for P_NEW */ if (isExtend) + { blockNum = smgrnblocks(smgr, forkNum); + /* Fail if relation is already at maximum possible length */ + if (blockNum == P_NEW) + ereport(ERROR, + (errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED), + errmsg("cannot extend relation %s beyond %u blocks", + relpath(smgr->smgr_rnode, forkNum), + P_NEW))); + } if (isLocalBuf) { diff --git a/src/backend/storage/smgr/md.c b/src/backend/storage/smgr/md.c index 7f1af3ffa0c..51617e17c18 100644 --- a/src/backend/storage/smgr/md.c +++ b/src/backend/storage/smgr/md.c @@ -437,7 +437,8 @@ mdextend(SMgrRelation reln, ForkNumber forknum, BlockNumber blocknum, /* * If a relation manages to grow to 2^32-1 blocks, refuse to extend it any * more --- we mustn't create a block whose number actually is - * InvalidBlockNumber. + * InvalidBlockNumber. (Note that this failure should be unreachable + * because of upstream checks in bufmgr.c.) */ if (blocknum == InvalidBlockNumber) ereport(ERROR, |