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    SubjectRe: [PATCH 07/12] perf_events: add LBR software filter support for Intel X86
    (2011/10/07 1:43), Peter Zijlstra wrote:
    > On Thu, 2011-10-06 at 17:32 +0200, Andi Kleen wrote:
    >>> + kernel_insn_init(&insn, kaddr);
    >>> + insn_get_opcode(&insn);
    >>
    >> This makes me uncomfortable. AFAIK that's the first use of the opcode
    >> decoder being used directly for user space. It has a quite large attack
    >> surface. Who says it cannot be exploited?
    >
    > You mean:
    > arch/x86/kernel/cpu/perf_event_intel_ds.c:intel_pmu_pebs_fixup_ip()
    > doesn't use the opcode decoder on user space code?
    >
    > ISTR Masami telling me they ran fuzzers on it, feeding it bad
    > instructions etc. But maybe he can tell more.

    I've tested it by decoding userspace libraries and binaries.
    It is also easy to test decoding with random binaries too :)
    I'll try to do that.

    Thanks,

    --
    Masami HIRAMATSU
    Software Platform Research Dept. Linux Technology Center
    Hitachi, Ltd., Yokohama Research Laboratory
    E-mail: masami.hiramatsu.pt@hitachi.com


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