Re:Reading privileged memory with a side-channel
by zetafunction on Wednesday January 03, 2018 @08:32PM
(#16067233)
Note that it's not just tabs sharing processes that's an issue: prior to the site isolation work, any iframe in the same page would always be in the same process as the main frame. With site isolation, it's possible to host cross-site [1] iframes in a separate process.
[1] Two pages are considered cross-site if they cannot use document.domain to become same origin. In practice, this means that the effective TLD + 1 component match.
This recent article contains a bit more detail on Site Isolation: https://arstechnica.com/gadgets/2017/12/chrome-63-offers-eve...
> Chrome's default model is, approximately, to use one process per tab. This more or less ensures that unrelated sites are kept in separate processes, but there are nuances to this set-up. Pages share a process if they are related through, for example, one opening another with JavaScript or iframes embedding (wherein one page is included as content within another page). Over the course of a single browsing session, one tab may be used to visit multiple different domains; they'll all potentially be opened within a single process. On top of this, if there are already too many Chrome processes running, Chrome will start opening new pages within existing processes, resulting in even unrelated pages sharing a process.
Which suggests there are a number of cases where multiple tabs could share a process.