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Commit 485fe695 authored by David Anderson's avatar David Anderson
Browse files

libsnapshot: Stop reading ops once we reach a footer. 

Bug: 168554689
Test: vts_libsnapshot_test
Change-Id: Id8b5ba33220028c856d3761832fe231fd93e94cd
parent 30d70441

fs_mgr/libsnapshot/cow_reader.cpp

+18 −6
Original line number Diff line number Diff line
@@ -18,6 +18,7 @@ 
#include <unistd.h>



#include <limits>

#include <optional>

#include <vector>



#include <android-base/file.h>
@@ -117,8 +118,7 @@ bool CowReader::ParseOps() { 
        PLOG(ERROR) << "lseek ops failed";

        return false;

    }

    uint64_t next_last_label = 0;

    bool has_next = false;

    std::optional<uint64_t> next_last_label;

    auto ops_buffer = std::make_shared<std::vector<CowOperation>>();

    if (has_footer_) ops_buffer->reserve(footer_.op.num_ops);

    uint64_t current_op_num = 0;
@@ -146,11 +146,23 @@ bool CowReader::ParseOps() { 
                has_last_label_ = true;

                last_label_ = current_op.source;

            } else {

                last_label_ = next_last_label;

                if (has_next) has_last_label_ = true;

                next_last_label = current_op.source;

                has_next = true;

                if (next_last_label) {

                    last_label_ = next_last_label.value();

                    has_last_label_ = true;

                }

                next_last_label = {current_op.source};

            }

        } else if (current_op.type == kCowFooterOp) {

            memcpy(&footer_.op, &current_op, sizeof(footer_.op));



            if (android::base::ReadFully(fd_, &footer_.data, sizeof(footer_.data))) {

                has_footer_ = true;

                if (next_last_label) {

                    last_label_ = next_last_label.value();

                    has_last_label_ = true;

                }

            }

            break;

        }

    }

fs_mgr/libsnapshot/snapshot_test.cpp

+3 −0
Original line number Diff line number Diff line
@@ -953,6 +953,9 @@ class SnapshotUpdateTest : public SnapshotTest { 
            if (!WriteRandomData(writer.get(), &hashes_[name])) {

                return AssertionFailure() << "Unable to write random data to snapshot " << name;

            }

            if (!writer->Finalize()) {

                return AssertionFailure() << "Unable to finalize COW for " << name;

            }

        } else {

            std::string path;

            auto res = MapUpdateSnapshot(name, &path);