perf record: Prevent reading invalid data in record__mmap_read

When record__mmap_read() requires data more than the size of ring
buffer, drop those data to avoid accessing invalid memory.

This can happen when reading from overwritable ring buffer, which
should be avoided. However, check this for robustness.

Signed-off-by: Wang Nan <wangnan0@huawei.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Zefan Li <lizefan@huawei.com>
Cc: pi3orama@163.com
Link: http://lkml.kernel.org/r/1463987628-163563-3-git-send-email-wangnan0@huawei.com
Signed-off-by: He Kuang <hekuang@huawei.com>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
index f3679c44d3f3d4b7c51bbb627375a315099b974d..f302cc937ca5bdd71af98e9747749eebe939723f 100644 (file)
--- a/tools/perf/builtin-record.c
+++ b/tools/perf/builtin-record.c
@@ -40,6 +40,7 @@
 #include <unistd.h>
 #include <sched.h>
 #include <sys/mman.h>
+#include <asm/bug.h>
 
 
 struct record {
@@ -98,6 +99,13 @@ static int record__mmap_read(struct record *rec, int idx)
        rec->samples++;
 
        size = head - old;
+       if (size > (unsigned long)(md->mask) + 1) {
+               WARN_ONCE(1, "failed to keep up with mmap data. (warn only once)\n");
+
+               md->prev = head;
+               perf_evlist__mmap_consume(rec->evlist, idx);
+               return 0;
+       }
 
        if ((old & md->mask) + size != (head & md->mask)) {
                buf = &data[old & md->mask];