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    Subject[PATCH 5.10 139/157] perf/x86/intel: Fix unchecked MSR access error caused by VLBR_EVENT
    Date
    From: Kan Liang <kan.liang@linux.intel.com>

    commit 2dc0572f2cef87425147658698dce2600b799bd3 upstream.

    On a Haswell machine, the perf_fuzzer managed to trigger this message:

    [117248.075892] unchecked MSR access error: WRMSR to 0x3f1 (tried to
    write 0x0400000000000000) at rIP: 0xffffffff8106e4f4
    (native_write_msr+0x4/0x20)
    [117248.089957] Call Trace:
    [117248.092685] intel_pmu_pebs_enable_all+0x31/0x40
    [117248.097737] intel_pmu_enable_all+0xa/0x10
    [117248.102210] __perf_event_task_sched_in+0x2df/0x2f0
    [117248.107511] finish_task_switch.isra.0+0x15f/0x280
    [117248.112765] schedule_tail+0xc/0x40
    [117248.116562] ret_from_fork+0x8/0x30

    A fake event called VLBR_EVENT may use the bit 58 of the PEBS_ENABLE, if
    the precise_ip is set. The bit 58 is reserved by the HW. Accessing the
    bit causes the unchecked MSR access error.

    The fake event doesn't support PEBS. The case should be rejected.

    Fixes: 097e4311cda9 ("perf/x86: Add constraint to create guest LBR event without hw counter")
    Reported-by: Vince Weaver <vincent.weaver@maine.edu>
    Signed-off-by: Kan Liang <kan.liang@linux.intel.com>
    Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
    Cc: stable@vger.kernel.org
    Link: https://lkml.kernel.org/r/1615555298-140216-2-git-send-email-kan.liang@linux.intel.com
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    arch/x86/events/intel/core.c | 3 +++
    1 file changed, 3 insertions(+)

    --- a/arch/x86/events/intel/core.c
    +++ b/arch/x86/events/intel/core.c
    @@ -3562,6 +3562,9 @@ static int intel_pmu_hw_config(struct pe
    return ret;

    if (event->attr.precise_ip) {
    + if ((event->attr.config & INTEL_ARCH_EVENT_MASK) == INTEL_FIXED_VLBR_EVENT)
    + return -EINVAL;
    +
    if (!(event->attr.freq || (event->attr.wakeup_events && !event->attr.watermark))) {
    event->hw.flags |= PERF_X86_EVENT_AUTO_RELOAD;
    if (!(event->attr.sample_type &

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