[release/7.0] Fix RegexOptions.NonBacktracking matching end anchors at timeout check boundaries #75308
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Tagging subscribers to this area: @dotnet/area-system-text-regularexpressions Issue DetailsBackport of #74525 to release/7.0 Customer ImpactTestingRiskIMPORTANT: Is this backport for a servicing release? If so and this change touches code that ships in a NuGet package, please make certain that you have added any necessary package authoring and gotten it explicitly reviewed.
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@danmoseley can we get your seal of approval, please? |
joperezr
approved these changes
Sep 8, 2022
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Approved. Correctness of regex is important. New code/new scenario, risk localized to new engine. |
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Approved and signed off. |
ghost
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Backport of #74525 to release/7.0
/cc @stephentoub @olsaarik
Customer Impact
This is fixing a correctness bug on our (new in .NET 7) NonBacktracking Regex engine. This is an edge case, which is why it wasn't caught during the development of the engine. Without this fix the code will incorrectly return that
Regex.IsMatch(string.Concat(new string('a', 999), "bc"), "^a*b$", RegexOptions.NonBacktracking)istrue. Issue is with the logic we have when we exit from loops for doing timeout checks, which is how @olsaarik found the issue.Testing
This was just an edge case missed originally. We have now added a test case to make sure it is not regressed.
Risk
Low. This is a brand new engine, and the changes on this PR are strictly about correctness.
IMPORTANT: Is this backport for a servicing release? If so and this change touches code that ships in a NuGet package, please make certain that you have added any necessary package authoring and gotten it explicitly reviewed.