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| author | Akilesh Kailash <akailash@google.com> | 2021-12-01 11:04:45 +0000 |
|---|---|---|
| committer | Akilesh Kailash <akailash@google.com> | 2021-12-01 20:37:56 +0000 |
| commit | 437522958814ef523d62d7fa988fef495cf7f6f4 (patch) | |
| tree | 51f37c08011f4d6b8f5b7f16c5a2ef286a613e8b | |
| parent | 4f95599b96bb6431e56cfb93ff4f7e31c4322edf (diff) | |
| download | core-437522958814ef523d62d7fa988fef495cf7f6f4.tar.gz | |
snapuserd: Address alignment fault on 32-bit systems
When the scratch space is mmap'ed, the metadata buffer
will be un-aligned. This may lead to alignment fault
on 32-bit systems. Address this by temporarily copying
it to buffer.
No perf impact as this code path is not in I/O path
and the copy is a for the size of metadata buffer which
is 8k.
Bug: 206426215
Test: Full and Incremental OTA on pixel
1: Compile snapuserd as 32 bit and reproduced the bug on pixel.
2: With fix - OTA applied successfully.
3: Reboot the device when merge was in-flight as the fix is primarily
in that path.
4: Verify merge completion and data integrity post merge.
Signed-off-by: Akilesh Kailash <akailash@google.com>
Change-Id: Icd4a21d6a61f1ab36e65994c06a4d049a2ee741c
Merged-In: I63c0d862057ebf138c9d1696a942030e30598739
| -rw-r--r-- | fs_mgr/libsnapshot/snapuserd_readahead.cpp | 8 |
1 files changed, 7 insertions, 1 deletions
diff --git a/fs_mgr/libsnapshot/snapuserd_readahead.cpp b/fs_mgr/libsnapshot/snapuserd_readahead.cpp index 16d5919a5..e55fea382 100644 --- a/fs_mgr/libsnapshot/snapuserd_readahead.cpp +++ b/fs_mgr/libsnapshot/snapuserd_readahead.cpp @@ -226,9 +226,15 @@ bool ReadAheadThread::ReconstructDataFromCow() { int num_ops = 0; int total_blocks_merged = 0; + // This memcpy is important as metadata_buffer_ will be an unaligned address and will fault + // on 32-bit systems + std::unique_ptr<uint8_t[]> metadata_buffer = + std::make_unique<uint8_t[]>(snapuserd_->GetBufferMetadataSize()); + memcpy(metadata_buffer.get(), metadata_buffer_, snapuserd_->GetBufferMetadataSize()); + while (true) { struct ScratchMetadata* bm = reinterpret_cast<struct ScratchMetadata*>( - (char*)metadata_buffer_ + metadata_offset); + (char*)metadata_buffer.get() + metadata_offset); // Done reading metadata if (bm->new_block == 0 && bm->file_offset == 0) { |