[PATCH v2 3/3] perf session: Avoid infinite loop if an event is truncated

[Petr Malat <oss@malat.biz>]

If an event was truncated at the end of a perf.data file larger than
MAP_SIZE, the event reading code ended up in an infinite loop. Break
this loop by making sure the mapping window is always shifting
towards the end of the file.

Fixes: bb1835a3b86c ("perf session: Fix decompression of PERF_RECORD_COMPRESSED records")
Fixes: 57fc032ad643 ("perf session: Avoid infinite loop when seeing invalid header.size")
Signed-off-by: Petr Malat <oss@malat.biz>
---
 tools/perf/util/session.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/tools/perf/util/session.c b/tools/perf/util/session.c
index 5f7bc5ad620f..79b2e93c1639 100644
--- a/tools/perf/util/session.c
+++ b/tools/perf/util/session.c
@@ -1,6 +1,7 @@
 // SPDX-License-Identifier: GPL-2.0
 #include <errno.h>
 #include <inttypes.h>
+#include <linux/err.h>
 #include <linux/kernel.h>
 #include <linux/zalloc.h>
 #include <api/fs/fs.h>
@@ -2182,6 +2183,12 @@ reader__process_events(struct reader *rd, struct perf_session *session,
 		}
 
 		page_offset = page_size * (head / page_size);
+		if (!page_offset) {
+			pr_err("%#" PRIx64 ": truncated event\n",
+					file_offset + head);
+			err = -EINVAL;
+			goto out;
+		}
 		file_offset += page_offset;
 		head -= page_offset;
 		goto remap;
-- 
2.20.1