linux-kernel - [PATCH] perf synthetic events: Avoid write of uninitialized memory.

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Message-Id: <20210309234945.419254-1-irogers@google.com>
Date:   Tue,  9 Mar 2021 15:49:45 -0800
From:   Ian Rogers <irogers@...gle.com>
To:     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>,
        linux-kernel@...r.kernel.org
Cc:     Stephane Eranian <eranian@...gle.com>,
        Ian Rogers <irogers@...gle.com>
Subject: [PATCH] perf synthetic events: Avoid write of uninitialized memory.

Account for alignment bytes in the zero-ing memset.

Signed-off-by: Ian Rogers <irogers@...gle.com>
---
 tools/perf/util/synthetic-events.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/tools/perf/util/synthetic-events.c b/tools/perf/util/synthetic-events.c
index b698046ec2db..31bf3dd6a1e0 100644
--- a/tools/perf/util/synthetic-events.c
+++ b/tools/perf/util/synthetic-events.c
@@ -424,7 +424,7 @@ int perf_event__synthesize_mmap_events(struct perf_tool *tool,
 
 	while (!io.eof) {
 		static const char anonstr[] = "//anon";
-		size_t size;
+		size_t size, aligned_size;
 
 		/* ensure null termination since stack will be reused. */
 		event->mmap2.filename[0] = '\0';
@@ -484,11 +484,12 @@ int perf_event__synthesize_mmap_events(struct perf_tool *tool,
 		}
 
 		size = strlen(event->mmap2.filename) + 1;
-		size = PERF_ALIGN(size, sizeof(u64));
+		aligned_size = PERF_ALIGN(size, sizeof(u64));
 		event->mmap2.len -= event->mmap.start;
 		event->mmap2.header.size = (sizeof(event->mmap2) -
-					(sizeof(event->mmap2.filename) - size));
-		memset(event->mmap2.filename + size, 0, machine->id_hdr_size);
+					(sizeof(event->mmap2.filename) - aligned_size));
+		memset(event->mmap2.filename + size, 0, machine->id_hdr_size +
+			(aligned_size - size));
 		event->mmap2.header.size += machine->id_hdr_size;
 		event->mmap2.pid = tgid;
 		event->mmap2.tid = pid;
-- 
2.30.1.766.gb4fecdf3b7-goog