[PATCH 4.9 01/42] perf event: Check ref_reloc_sym before using it

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

From: Igor Lubashev <ilubashe@akamai.com>

commit e9a6882f267a8105461066e3ea6b4b6b9be1b807 upstream.

Check for ref_reloc_sym before using it instead of checking
symbol_conf.kptr_restrict and relying solely on that check.

Reported-by: Mathieu Poirier <mathieu.poirier@linaro.org>
Signed-off-by: Igor Lubashev <ilubashe@akamai.com>
Tested-by: Mathieu Poirier <mathieu.poirier@linaro.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Alexey Budankov <alexey.budankov@linux.intel.com>
Cc: James Morris <jmorris@namei.org>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Suzuki Poulouse <suzuki.poulose@arm.com>
Cc: linux-arm-kernel@lists.infradead.org
Link: http://lkml.kernel.org/r/1566869956-7154-2-git-send-email-ilubashe@akamai.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Alexander Dahl <ada@thorsis.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 tools/perf/util/event.c |    7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

--- a/tools/perf/util/event.c
+++ b/tools/perf/util/event.c
@@ -682,11 +682,13 @@ int perf_event__synthesize_kernel_mmap(s
 	int err;
 	union perf_event *event;
 
-	if (symbol_conf.kptr_restrict)
-		return -1;
 	if (map == NULL)
 		return -1;
 
+	kmap = map__kmap(map);
+	if (!kmap->ref_reloc_sym)
+		return -1;
+
 	/*
 	 * We should get this from /sys/kernel/sections/.text, but till that is
 	 * available use this, and after it is use this as a fallback for older
@@ -710,7 +712,6 @@ int perf_event__synthesize_kernel_mmap(s
 		event->header.misc = PERF_RECORD_MISC_GUEST_KERNEL;
 	}
 
-	kmap = map__kmap(map);
 	size = snprintf(event->mmap.filename, sizeof(event->mmap.filename),
 			"%s%s", mmap_name, kmap->ref_reloc_sym->name) + 1;
 	size = PERF_ALIGN(size, sizeof(u64));