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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 | 7430c774209cd98bbc33076cc3c07497c1086d9a (patch) | |
| tree | a428d21f93020d1332a61ad9e2a819f692d9dc6c | |
| parent | b5ec22bf5e8f19964f7c7d7ef357ff947a38c7fc (diff) | |
| download | postgresql-7430c774209cd98bbc33076cc3c07497c1086d9a.tar.gz postgresql-7430c774209cd98bbc33076cc3c07497c1086d9a.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 4b296a22c45..ffc6056c60c 100644 --- a/src/backend/storage/buffer/bufmgr.c +++ b/src/backend/storage/buffer/bufmgr.c @@ -830,7 +830,16 @@ 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 1e12cfad8e8..b4bca7eed6f 100644 --- a/src/backend/storage/smgr/md.c +++ b/src/backend/storage/smgr/md.c @@ -426,7 +426,8 @@ 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, |