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    Subject[PATCH V31 23/25] Lock down perf when in confidentiality mode
    From
    From: David Howells <dhowells@redhat.com>

    Disallow the use of certain perf facilities that might allow userspace to
    access kernel data.

    Signed-off-by: David Howells <dhowells@redhat.com>
    Signed-off-by: Matthew Garrett <mjg59@google.com>
    Cc: Peter Zijlstra <peterz@infradead.org>
    Cc: Ingo Molnar <mingo@redhat.com>
    Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
    ---
    kernel/events/core.c | 6 ++++++
    1 file changed, 6 insertions(+)

    diff --git a/kernel/events/core.c b/kernel/events/core.c
    index 3cd13a30f732..6ad3d83c091c 100644
    --- a/kernel/events/core.c
    +++ b/kernel/events/core.c
    @@ -10461,6 +10461,12 @@ SYSCALL_DEFINE5(perf_event_open,
    return -EINVAL;
    }

    + if ((attr.sample_type & PERF_SAMPLE_REGS_INTR) &&
    + kernel_is_locked_down("PERF_SAMPLE_REGS_INTR",
    + LOCKDOWN_CONFIDENTIALITY))
    + /* REGS_INTR can leak data, lockdown must prevent this */
    + return -EPERM;
    +
    /* Only privileged users can get physical addresses */
    if ((attr.sample_type & PERF_SAMPLE_PHYS_ADDR) &&
    perf_paranoid_kernel() && !capable(CAP_SYS_ADMIN))
    --
    2.21.0.392.gf8f6787159e-goog
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