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    SubjectRe: [PATCH 00/11 v3] x86: load FPU registers on return to userland
    On 2018-10-04 12:45:08 [-0400], Rik van Riel wrote:
    > Wait, so any thread can bypass its memory protection
    > keys, even if there is a seccomp filter preventing
    > it from calling the PKRU syscalls?

    We have SYS_pkey_alloc +free and SYS_pkey_mprotect. For read/ write of
    the register value, libc is using and opcodes.

    > Is that intended?

    Either that or it ended like that because someone failed to attend a
    meeting where this was discussed. Here is something from pkeys(7):

    | Protection keys have the potential to add a layer of security and
    | reliability to applications. But they have not been primarily designed as a
    | security feature. For instance, WRPKRU is a completely unprivileged
    | instruction, so pkeys are useless in any case that an attacker controls the
    | PKRU register or can execute arbitrary instructions.

    Sebastian

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