[PATCH 09/15] perf tools: validate perf event header size

[Adrian Hunter <adrian.hunter@intel.com>]

'size' includes the header so must be at least
'sizeof(struct perf_event_header)'.  Error out
immediately if that is not the case.  Also
don't byte-swap the header until it is actually
"fetched" from the mmap region.

Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
---
 tools/perf/util/session.c | 14 ++++++++------
 1 file changed, 8 insertions(+), 6 deletions(-)

diff --git a/tools/perf/util/session.c b/tools/perf/util/session.c
index 19ea888..7e0d605 100644
--- a/tools/perf/util/session.c
+++ b/tools/perf/util/session.c
@@ -1094,8 +1094,10 @@ more:
 		perf_event_header__bswap(&event->header);
 
 	size = event->header.size;
-	if (size == 0)
-		size = 8;
+	if (size < sizeof(struct perf_event_header)) {
+		pr_err("bad event header size\n");
+		goto out_err;
+	}
 
 	if (size > cur_size) {
 		void *new = realloc(buf, size);
@@ -1161,12 +1163,12 @@ fetch_mmaped_event(struct perf_session *session,
 
 	event = (union perf_event *)(buf + head);
 
-	if (session->header.needs_swap)
-		perf_event_header__bswap(&event->header);
-
 	if (head + event->header.size > mmap_size)
 		return NULL;
 
+	if (session->header.needs_swap)
+		perf_event_header__bswap(&event->header);
+
 	return event;
 }
 
@@ -1245,7 +1247,7 @@ more:
 
 	size = event->header.size;
 
-	if (size == 0 ||
+	if (size < sizeof(struct perf_event_header) ||
 	    perf_session__process_event(session, event, tool, file_pos) < 0) {
 		pr_err("%#" PRIx64 " [%#x]: failed to process type: %d\n",
 		       file_offset + head, event->header.size,
-- 
1.7.11.7