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Fix TOCTOU race in LogOptions.CreateLogger (#252) #253

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Merged
ptr727 merged 1 commit into from
Jul 10, 2026
Merged

Fix TOCTOU race in LogOptions.CreateLogger (#252) #253

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9 changes: 5 additions & 4 deletions LanguageTags/LogOptions.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -18,7 +18,7 @@ namespace ptr727.LanguageTags;
/// </list>
/// <para>
/// Note that loggers are created and cached at the time of use by each class instance. Changes to <see cref="LoggerFactory"/>
/// after a logger has been created will not affect existing cached loggers—only new logger requests will use the updated configuration.
/// after a logger has been created will not affect existing cached loggers. Only new logger requests will use the updated configuration.
/// </para>
/// </remarks>
public static class LogOptions
Expand Down Expand Up @@ -75,9 +75,10 @@ internal static ILogger CreateLogger(string categoryName)
{
ArgumentException.ThrowIfNullOrWhiteSpace(categoryName);

// LoggerFactory -> NullLogger
return !ReferenceEquals(LoggerFactory, NullLoggerFactory.Instance)
? LoggerFactory.CreateLogger(categoryName)
// Read once so a concurrent swap cannot split the check and the create across two instances.
ILoggerFactory factory = LoggerFactory;
return !ReferenceEquals(factory, NullLoggerFactory.Instance)
? factory.CreateLogger(categoryName)
: NullLogger.Instance;
}
}