perf/x86/intel/pt: Fix kernel address filter's offset validation

The kernel_ip() filter is used mostly by the DS/LBR code to look at the
branch addresses, but Intel PT also uses it to validate the address
filter offsets for kernel addresses, for which it is not sufficient:
supplying something in bits 64:48 that's not a sign extension of the lower
address bits (like 0xf00d000000000000) throws a #GP.

This patch adds address validation for the user supplied kernel filters.
Reported-by: Adrian Hunter <adrian.hunter@intel.com>
Signed-off-by: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Cc: Arnaldo Carvalho de Melo <acme@infradead.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Stephane Eranian <eranian@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vince Weaver <vincent.weaver@maine.edu>
Cc: stable@vger.kernel.org # v4.7
Cc: stable@vger.kernel.org#v4.7
Cc: vince@deater.net
Link: http://lkml.kernel.org/r/20160915151352.21306-3-alexander.shishkin@linux.intel.comSigned-off-by: Ingo Molnar <mingo@kernel.org>

arch/x86/events/intel/pt.c

@@ -1074,6 +1074,11 @@ static void pt_addr_filters_fini(struct perf_event *event)
 	event->hw.addr_filters = NULL;
 }
 
+static inline bool valid_kernel_ip(unsigned long ip)
+{
+	return virt_addr_valid(ip) && kernel_ip(ip);
+}
+
 static int pt_event_addr_filters_validate(struct list_head *filters)
 {
 	struct perf_addr_filter *filter;
@@ -1084,7 +1089,7 @@ static int pt_event_addr_filters_validate(struct list_head *filters)
 		if (!filter->range || !filter->size)
 			return -EOPNOTSUPP;
 
-		if (!filter->inode && !kernel_ip(filter->offset))
+		if (!filter->inode && !valid_kernel_ip(filter->offset))
 			return -EINVAL;
 
 		if (++range > pt_cap_get(PT_CAP_num_address_ranges))