grsecurity: Teardown of a Failed Linux LTS Spectre Fix

Thisgrsecurity blog entry looks at how an ineffective Spectre fix found itsway into the stable kernel releases. If one looks past the advertising,it's a good summary of how the kernel processes can produce the wrongresult. "Despite this warning, this code was merged into ThomasGleixner's x86/tip tree verbatim, as can be seen here.Prior to merging the fix for 5.3-rc1, Linus Torvalds noticed the warning asseen on the LKML mailing list here and fixed it correctly.However, when the actual mergeof the tree was performed, no mention was made of the correction to thefix, and with no specific commit mentioning the correction and fixing italone, everyone else's processes that depended on cherry-picking specificcommits ended up grabbing the bad warning-inducing change.As a further failure, instead of looking at Linus' correct fix (observableby checking out the master tree at the time), the approach seems to havebeen to naively silence the warning by simply swapping the order of the twolines."