[issue21131] test_faulthandler.test_register_chain fails on 64bit ppc/arm with kernel >= 3.10
STINNER Victor
report at bugs.python.org
Wed Aug 14 08:18:16 EDT 2019
STINNER Victor <vstinner at redhat.com> added the comment:
Ah, I found the recent change about XSAVE: it is a fix for CVE-2018-3665 vulnerability.
"The software mitigation for this is to switch to an "eager" / immediate FPU state save and restore, in both kernels and hypervisors."
"On Intel and AMD x86 processors, operating systems and hypervisors often use what is referred to as a deferred saving and restoring method of the x86 FPU state, as part of performance optimization. This is done in a "lazy" on-demand fashion."
"It was found that due to the "lazy" approach, the x86 FPU states or FPU / XMM / AVX512 register content, could leak across process, or even VM boundaries, giving attackers possibilities to read private data from other processes, when using speculative execution side channel gadgets."
https://www.suse.com/support/kb/doc/?id=7023076
See also: https://en.wikipedia.org/wiki/Lazy_FP_state_restore
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