fix(spanner): avoid use-after-move bugs #7588
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@devbww and I debugged a use-after move issue that boiled down to these two Row iterators inspecting a data member (e.g., `row_` and `tup_`) on subsequent invocations of `op++`, after a caller may have rightfully moved the object. To avoid this issue, we keep an extra bool in both iterators to avoid the need to inspect the StatusOr data member again. Note: This issue didn't show up in our code or builds. It showed up only when trying to make a different change to `Status`. Kudos to @devbww for helping to track this down.
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devbww
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Nov 12, 2021
google/cloud/spanner/row_test.cc
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| TEST(TupleStreamIterator, MovedFromValueOk) { | ||
| std::vector<Row> rows; | ||
| rows.emplace_back(MakeTestRow({{"num", Value(42)}})); | ||
| rows.emplace_back(MakeTestRow({{"num", Value(42)}})); |
devbww
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Nov 12, 2021
google/cloud/spanner/row_test.cc
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| EXPECT_NE(it, end); | ||
| auto row = std::move(*it); | ||
| EXPECT_STATUS_OK(row); | ||
| EXPECT_EQ(1, row->size()); |
Codecov Report
@@ Coverage Diff @@
## main #7588 +/- ##
=======================================
Coverage 95.24% 95.24%
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Files 1252 1252
Lines 112850 112894 +44
=======================================
+ Hits 107483 107529 +46
+ Misses 5367 5365 -2
Continue to review full report at Codecov.
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devbww
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Nov 13, 2021
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Nov 19, 2021
Similar to: googleapis#7588 This code allowed callers to (rightfully) move-out the `StatusOr` that was held in `current_`. Therefore, it's a bug if we then consult the status of `current_.ok()`, because it may be in a moved-from state. The fix is to track the `current_ok_` bit separately, so that we only ever assign to `current_` and never read it after it could have been moved.
devjgm
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that referenced
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Nov 19, 2021
Similar to: googleapis#7588 This code allowed callers to (rightfully) move-out the `StatusOr` that was held in `current_`. Therefore, it's a bug if we then consult the status of `current_.ok()`, because it may be in a moved-from state. The fix is to track the `current_ok_` bit separately, so that we only ever assign to `current_` and never read it after it could have been moved.
devjgm
added a commit
that referenced
this pull request
Nov 19, 2021
Similar to: #7588 This code allowed callers to (rightfully) move-out the `StatusOr` that was held in `current_`. Therefore, it's a bug if we then consult the status of `current_.ok()`, because it may be in a moved-from state. The fix is to track the `current_ok_` bit separately, so that we only ever assign to `current_` and never read it after it could have been moved.
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@devbww and I debugged a use-after move issue that boiled down to these
two Row iterators inspecting a data member (e.g.,
row_andtup_) onsubsequent invocations of
op++, after a caller may have rightfullymoved the object. To avoid this issue, we keep an extra bool in both
iterators to avoid the need to inspect the StatusOr data member again.
Note: This issue didn't show up in our code or builds. It showed up only
when trying to make a different change to
Status.Kudos to @devbww for helping to track this down.
This change is