Fix a bug in compaction reads causing checksum mismatches and asan errors

[sagar0]

Fixed a bug in compaction reads due to which incorrect number of bytes were being read/utilized. The bug was introduced in #5498 , resulting in "Corruption: block checksum mismatch" and "heap-buffer-overflow" asan errors in our tests.

#5498 was introduced recently and is not in any released versions.

ASAN:

> ==2280939==ERROR: AddressSanitizer: heap-buffer-overflow on address 0x6250005e83da at pc 0x000000d57f62 bp 0x7f954f483770 sp 0x7f954f482f20
> === How to use this, how to get the raw stack trace, and more: fburl.com/ASAN ===
> READ of size 4 at 0x6250005e83da thread T4
> SCARINESS: 27 (4-byte-read-heap-buffer-overflow-far-from-bounds)

>      #0 tests+0xd57f61                           __asan_memcpy
>      #1 rocksdb/src/util/coding.h:124            rocksdb::DecodeFixed32(char const*)
>      #2 rocksdb/src/table/block_fetcher.cc:39    rocksdb::BlockFetcher::CheckBlockChecksum()
>      #3 rocksdb/src/table/block_fetcher.cc:99    rocksdb::BlockFetcher::TryGetFromPrefetchBuffer()
>      #4 rocksdb/src/table/block_fetcher.cc:209   rocksdb::BlockFetcher::ReadBlockContents()
>      #5 rocksdb/src/table/block_based/block_based_table_reader.cc:93 rocksdb::(anonymous namespace)::ReadBlockFromFile(rocksdb::RandomAccessFileReader*, rocksdb::FilePrefetchBuffer*, rocksdb::Footer const&, rocksdb::ReadOptions const&, rocksdb::BlockHandle const&, std::unique_ptr<...>*, rocksdb::ImmutableCFOptions const&, bool, bool, rocksdb::UncompressionDict
 const&, rocksdb::PersistentCacheOptions const&, unsigned long, unsigned long, rocksdb::MemoryAllocator*, bool)
>      #6 rocksdb/src/table/block_based/block_based_table_reader.cc:2331 rocksdb::BlockBasedTable::RetrieveBlock(rocksdb::FilePrefetchBuffer*, rocksdb::ReadOptions const&, rocksdb::BlockHandle const&, rocksdb::UncompressionDict const&, rocksdb::CachableEntry<...>*, rocksdb::BlockType, rocksdb::GetContext*, rocksdb::BlockCacheLookupContext*, bool) const
>      #7 rocksdb/src/table/block_based/block_based_table_reader.cc:2090 rocksdb::DataBlockIter* rocksdb::BlockBasedTable::NewDataBlockIterator<...>(rocksdb::ReadOptions const&, rocksdb::BlockHandle const&, rocksdb::DataBlockIter*, rocksdb::BlockType, bool, bool, rocksdb::GetContext*, rocksdb::BlockCacheLookupContext*, rocksdb::Status, rocksdb::FilePrefetchBuffe
r*, bool) const
>      #8 rocksdb/src/table/block_based/block_based_table_reader.cc:2720 rocksdb::BlockBasedTableIterator<...>::InitDataBlock()
>      #9 rocksdb/src/table/block_based/block_based_table_reader.cc:2607 rocksdb::BlockBasedTableIterator<...>::SeekToFirst()
>     #10 rocksdb/src/table/iterator_wrapper.h:83  rocksdb::IteratorWrapperBase<...>::SeekToFirst()
>     #11 rocksdb/src/table/merging_iterator.cc:100 rocksdb::MergingIterator::SeekToFirst()
>     #12 rocksdb/compaction/compaction_job.cc:877 rocksdb::CompactionJob::ProcessKeyValueCompaction(rocksdb::CompactionJob::SubcompactionState*)
>     #13 rocksdb/compaction/compaction_job.cc:590 rocksdb::CompactionJob::Run()
>     #14 rocksdb/db_impl/db_impl_compaction_flush.cc:2689 rocksdb::DBImpl::BackgroundCompaction(bool*, rocksdb::JobContext*, rocksdb::LogBuffer*, rocksdb::DBImpl::PrepickedCompaction*, rocksdb::Env::Priority)
>     #15 rocksdb/db_impl/db_impl_compaction_flush.cc:2248 rocksdb::DBImpl::BackgroundCallCompaction(rocksdb::DBImpl::PrepickedCompaction*, rocksdb::Env::Priority)
>     #16 rocksdb/db_impl/db_impl_compaction_flush.cc:2024 rocksdb::DBImpl::BGWorkCompaction(void*)
>     #23 rocksdb/src/util/threadpool_imp.cc:266   rocksdb::ThreadPoolImpl::Impl::BGThread(unsigned long)
>     #24 rocksdb/src/util/threadpool_imp.cc:307   rocksdb::ThreadPoolImpl::Impl::BGThreadWrapper(void*)

Test Plan:
Verified that this fixes the fb-internal Logdevice test which caught the issue.

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[facebook-github-bot]

@sagar0 merged this pull request in 84c5c9a.