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

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Message-Id: <20201124095923.3683-3-oss@malat.biz>
Date:   Tue, 24 Nov 2020 10:59:21 +0100
From:   Petr Malat <oss@...at.biz>
To:     linux-kernel@...r.kernel.org
Cc:     Petr Malat <oss@...at.biz>, Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...hat.com>,
        Namhyung Kim <namhyung@...nel.org>,
        Adrian Hunter <adrian.hunter@...el.com>,
        "Paul A. Clarke" <pc@...ibm.com>,
        Kan Liang <kan.liang@...ux.intel.com>,
        Alexey Budankov <alexey.budankov@...ux.intel.com>
Subject: [PATCH 3/3] perf session: Avoid infinite loop if an event is truncated

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@...at.biz>
---
 tools/perf/util/session.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/tools/perf/util/session.c b/tools/perf/util/session.c
index e57b0d09d196..b73b85d99628 100644
--- a/tools/perf/util/session.c
+++ b/tools/perf/util/session.c
@@ -2168,6 +2168,12 @@ reader__process_events(struct reader *rd, struct perf_session *session,
 		}
 
 		page_offset = page_size * (head / page_size);
+		if (!page_offset) {
+			pr_err("%#" PRIx64 " [%#x]: truncated event\n",
+					file_offset + head);
+			err = -EINVAL;
+			goto out;
+		}
 		file_offset += page_offset;
 		head -= page_offset;
 		goto remap;
-- 
2.20.1