[Webkit-unassigned] [Bug 216962] New: IndexedDB Index Corruption after upgrade from iOS 13 to iOS 14

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=216962

            Bug ID: 216962
           Summary: IndexedDB Index Corruption after upgrade from iOS 13
                    to iOS 14
           Product: WebKit
           Version: Safari 14
          Hardware: iPhone / iPad
                OS: Other
            Status: NEW
          Severity: Critical
          Priority: P2
         Component: New Bugs
          Assignee: webkit-unassigned at lists.webkit.org
          Reporter: dvpdiner2 at gmail.com

r255318 introduced a change to how IDB Indexes are stored in the SQLite backing store. It moves from per-ObjectStore index IDs to per-Database index IDs, and attempts to perform a migration. This migration is run on iOS 14 when launching an app whose WKWebView IndexedDB databases were created on iOS 13.

There's a flaw in the migration process that can result in multiple indexes being updated to have the same ID, and corrupting the associated IndexRecords data. Once this happens, it appears to be impossible to recover the correct indexes.

A detailed walkthrough of how this happens to the IDB indices in our app can be found here: https://gist.github.com/dpogue/53d529310355697a0bfdf17644a17840

It only happens in some pretty specific situations, but it's a pretty serious problem.

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