4.7-stable review patch.  If anyone has any objections, please let me know.


From: Jiri Olsa <jo...@kernel.org>

commit 79d102cbfd2e9d94257fcc7c82807ef1cdf80322 upstream.

Yanqiu Zhang reported kernel panic when using mbm event
on system where CQM is detected but without mbm event
support, like with perf:

  # perf stat -e 'intel_cqm/event=3/' -a

  BUG: unable to handle kernel NULL pointer dereference at 0000000000000020
  IP: [<ffffffff8100d64c>] update_sample+0xbc/0xe0
   [<ffffffff8100d688>] __intel_mbm_event_init+0x18/0x20
   [<ffffffff81113d6b>] flush_smp_call_function_queue+0x7b/0x160
   [<ffffffff81114853>] generic_smp_call_function_single_interrupt+0x13/0x60
   [<ffffffff81052017>] smp_call_function_interrupt+0x27/0x40
   [<ffffffff816fb06c>] call_function_interrupt+0x8c/0xa0

The reason is that we currently allow to init mbm event
even if mbm support is not detected.  Adding checks for
both cqm and mbm events and support into cqm's event_init.

Fixes: 33c3cc7acfd9 ("perf/x86/mbm: Add Intel Memory B/W Monitoring enumeration 
and init")
Reported-by: Yanqiu Zhang <yanqz...@redhat.com>
Signed-off-by: Jiri Olsa <jo...@redhat.com>
Acked-by: Peter Zijlstra <a.p.zijls...@chello.nl>
Cc: Vikas Shivappa <vikas.shiva...@linux.intel.com>
Cc: Tony Luck <tony.l...@intel.com>
Signed-off-by: Thomas Gleixner <t...@linutronix.de>
Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>

 arch/x86/events/intel/cqm.c |    9 +++++++++
 1 file changed, 9 insertions(+)

--- a/arch/x86/events/intel/cqm.c
+++ b/arch/x86/events/intel/cqm.c
@@ -458,6 +458,11 @@ static void __intel_cqm_event_count(void
 static void init_mbm_sample(u32 rmid, u32 evt_type);
 static void __intel_mbm_event_count(void *info);
+static bool is_cqm_event(int e)
+       return (e == QOS_L3_OCCUP_EVENT_ID);
 static bool is_mbm_event(int e)
        return (e >= QOS_MBM_TOTAL_EVENT_ID && e <= QOS_MBM_LOCAL_EVENT_ID);
@@ -1366,6 +1371,10 @@ static int intel_cqm_event_init(struct p
             (event->attr.config > QOS_MBM_LOCAL_EVENT_ID))
                return -EINVAL;
+       if ((is_cqm_event(event->attr.config) && !cqm_enabled) ||
+           (is_mbm_event(event->attr.config) && !mbm_enabled))
+               return -EINVAL;
        /* unsupported modes and filters */
        if (event->attr.exclude_user   ||
            event->attr.exclude_kernel ||

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