Bug 119343

Summary:

Some cleanup in JSValue::get

Product:

WebKit

Reporter:

Gavin Barraclough <barraclough>

Component:

JavaScriptCore

Assignee:

Gavin Barraclough <barraclough>

Status:

RESOLVED FIXED

Severity:

Normal

CC:

cdumez, commit-queue, mark.lam, simon.fraser, spena

Priority:

Version:

528+ (Nightly build)

Hardware:

Unspecified

OS:

Unspecified

Attachments:

Description	Flags
fix	ggaren: review+, buildbot: commit-queue-

Gavin Barraclough

Reported 2013-07-31 10:44:20 PDT

JSValue::get is implemented to: 1) Check if the value is a cell – if not, synthesize a prototype to search, 2) call getOwnPropertySlot on the cell, 3) if this returns false, cast to JSObject to get the prototype, and walk the prototype chain. By all rights this should crash when passed a string and accessing a property that does not exist, because the string is a cell, getOwnPropertySlot should return false, and the cast to JSObject should be unsafe. To work around this, JSString::getOwnPropertySlot actually implements 'get' functionality - searching the prototype chain, and faking out a return value of undefined if no property is found. This is a huge hazard, since fixing JSString::getOwnPropertySlot or calling getOwnPropertySlot on cells from elsewhere would introduce bugs. Fortunately it is only ever called in this one place. The fix here is to move getOwnPropertySlot onto JSObjecte and end this madness - cells don't have property slots anyway.

Attachments
fix (93.13 KB, patch) 2013-07-31 10:48 PDT, Gavin Barraclough	ggaren: review+ buildbot: commit-queue-	Details Formatted Diff Diff
View All Add attachment proposed patch, testcase, etc.