diff options
| 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 | ca1dd6234049bd5f9c06c45b0bffc867120eaac3 (patch) | |
| tree | d618a34ad0f517b2cd3faf42d21cec9437c79fa0 | |
| parent | f77489046d172b3111d4d588479fc4e7444ec36b (diff) | |
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 236dc15f96e..bafe91ab0d6 100644 --- a/src/backend/storage/buffer/bufmgr.c +++ b/src/backend/storage/buffer/bufmgr.c @@ -726,7 +726,16 @@ 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 070660253c9..8c98a114354 100644 --- a/src/backend/storage/smgr/md.c +++ b/src/backend/storage/smgr/md.c @@ -549,7 +549,8 @@ 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, |