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author | anand76 <anand76@devvm4702.ftw0.facebook.com> | 2022-12-21 09:15:53 -0800 |
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committer | Facebook GitHub Bot <facebook-github-bot@users.noreply.github.com> | 2022-12-21 09:15:53 -0800 |
commit | dbf37c290ae0cbf1532f706942c098380cb9c53a (patch) | |
tree | 0e3d48146055eef48a24877331524188ca6778ab /file/file_prefetch_buffer.cc | |
parent | 53b703eafef16c20bad64171f1dcca8cc98eefa0 (diff) |
Fix async prefetch heap use after free (#11049)
Summary:
This PR fixes a heap use after free bug in the async prefetch code that happens in the following scenario -
1. Scan thread starts 2 async reads for Seek, one for the seek block and one for prefetching
2. Before the first read in https://github.com/facebook/rocksdb/issues/1 completes, another thread reads and loads the block in cache
3. The first scan thread finds the block in cache, continues and the next block cache miss is for a block that spans the boundary of the 2 prefetch buffers, and the 1st read is complete but the 2nd one is not complete yet
4. The scan thread will reallocate (i.e free the old buffer and allocate a new one) the 2nd prefetch buffer, and the in-progress prefetch is orphaned
5. The orphaned prefetch finally completes, resulting in a use after free
Also add a few asserts to surface bugs earlier in the crash tests.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/11049
Test Plan: Repro with db_stress and verify the fix
Reviewed By: akankshamahajan15
Differential Revision: D42181118
Pulled By: anand1976
fbshipit-source-id: 1ac55d2f64a89ce128c1c574262b8aa7d82eb8cc
Diffstat (limited to 'file/file_prefetch_buffer.cc')
-rw-r--r-- | file/file_prefetch_buffer.cc | 15 |
1 files changed, 14 insertions, 1 deletions
diff --git a/file/file_prefetch_buffer.cc b/file/file_prefetch_buffer.cc index 9ea9129e2..4ac0d0504 100644 --- a/file/file_prefetch_buffer.cc +++ b/file/file_prefetch_buffer.cc @@ -247,10 +247,14 @@ void FilePrefetchBuffer::AbortAllIOs() { // Release io_handles. if (bufs_[curr_].io_handle_ != nullptr && bufs_[curr_].del_fn_ != nullptr) { DestroyAndClearIOHandle(curr_); + } else { + bufs_[curr_].async_read_in_progress_ = false; } if (bufs_[second].io_handle_ != nullptr && bufs_[second].del_fn_ != nullptr) { DestroyAndClearIOHandle(second); + } else { + bufs_[second].async_read_in_progress_ = false; } } @@ -325,7 +329,16 @@ Status FilePrefetchBuffer::HandleOverlappingData( uint64_t& tmp_offset, size_t& tmp_length) { Status s; size_t alignment = reader->file()->GetRequiredBufferAlignment(); - uint32_t second = curr_ ^ 1; + uint32_t second; + + // Check if the first buffer has the required offset and the async read is + // still in progress. This should only happen if a prefetch was initiated + // by Seek, but the next access is at another offset. + if (bufs_[curr_].async_read_in_progress_ && + IsOffsetInBufferWithAsyncProgress(offset, curr_)) { + PollAndUpdateBuffersIfNeeded(offset); + } + second = curr_ ^ 1; // If data is overlapping over two buffers, copy the data from curr_ and // call ReadAsync on curr_. |