perf synthetic events: Avoid write of uninitialized memory when generating PERF_RECOR...

Account for alignment bytes in the zero-ing memset.

Fixes: 1a853e36871b533c ("perf record: Allow specifying a pid to record")
Signed-off-by: Ian Rogers <irogers@google.com>
Acked-by: Jiri Olsa <jolsa@redhat.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Link: http://lore.kernel.org/lkml/20210309234945.419254-1-irogers@google.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

diff --git a/tools/perf/util/synthetic-events.c b/tools/perf/util/synthetic-events.c
index 5dd4516..dff1781 100644 (file)
--- 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 @@ out:
                }
 
                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;