Linux Fixes Spectre V1 SWAPGS Mitigation After Being Partially Borked Since Last Year

[phoronix]

Phoronix: Linux Fixes Spectre V1 SWAPGS Mitigation After Being Partially Borked Since Last Year

This week's set of "x86/urgent" changes for the Linux 5.16-rc4 kernel due out later today has some Spectre V1 fixes after kernel commits last year ended up partially messing things up around its SWAPGS handling. These fixes in turn will also likely be back-ported to relevant stable kernel series...

https://www.phoronix.com/scan.php?page=news_item&px=Linux-5.16-rc4-Fixing-SWAPGS

[Developer12]

Another example of something the BSDs are missing out on completely, for not mitigaing Spectre Variant 1 *at all.*

[Alex/AT]

Another example of something the BSDs are missing out on completely, for not mitigaing Spectre Variant 1 *at all.*

Honestly, last days with more and more perf sucked I do feel it should all be just disabled by default, and enabled only by some PARANOID_BUILD compile time option.

[Developer12]

Honestly, last days with more and more perf sucked I do feel it should all be just disabled by default, and enabled only by some PARANOID_BUILD compile time option.

It's called booting with mitigations=off and it's a stupid thing to do with PoC javascript in the wild that uses spectre to read from neighboring browser tabs/processes

Unless you like the idea of some random ad script stealing all your passwords from your password manager or reading your banking page

[Alex/AT]

Nope, mitigations=off does not disable all the crap. Especially not the code paths that specifically exist to put mitigations in place when enabled.
And no, I don't see any 'random ad script exploit' proof of concept I tested even trying to start working somehow in my browser, with all the mitigations off.
Given I'm on AMD CPU of course. Meltdown worked on Intels for sure, L1TF is less probable to be exploited, but yeah, it worked on Intel CPUs again.
Spectre is more of an unexploitable hoax, theoretically dangerous but working in labs only, with ideally exploitable conditions set up for it to work.