Bug 255162

Summary: Accessing null RemoteScrollingCoordinatorProxy in [WKWebViewIOS _didFinishScrolling]
Product: WebKit Reporter: Abrar Rahman Protyasha <a_protyasha>
Component: ScrollingAssignee: Nobody <webkit-unassigned>
Status: RESOLVED FIXED    
Severity: Normal CC: a_protyasha, simon.fraser, webkit-bug-importer
Priority: P1 Keywords: InRadar
Version: WebKit Nightly Build   
Hardware: Unspecified   
OS: Unspecified   

Description Abrar Rahman Protyasha 2023-04-07 12:03:49 PDT 
We're seeing runtime crashes at [WKWebViewIOS _didFinishScrolling] in situations where a web view is closed out during a scroll operation.

This regression surfaced from https://commits.webkit.org/260975@main because it (correctly) changed the relative order of destruction between the `DrawingAreaProxy` and the `RemoteScrollingCoordinatorProxy` (and the `RemoteScrollingTree` it encompasses), which meant that there could be situations where closing or switching out a web view in the middle of a scroll operation could lead to a null deref of the `RemoteScrollingCoordinatorProxy` held by the `WebPageProxy`.
Comment 1 Abrar Rahman Protyasha 2023-04-07 12:05:10 PDT 
rdar://106894608
Comment 2 Abrar Rahman Protyasha 2023-04-07 15:04:38 PDT 
Pull request: https://github.com/WebKit/WebKit/pull/12532
Comment 3 EWS 2023-04-07 21:58:46 PDT 
Committed 262748@main (2aa252bfd9f1): <https://commits.webkit.org/262748@main>

Reviewed commits have been landed. Closing PR #12532 and removing active labels.