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[tip:perf/urgent] perf record: Prevent reading invalid data in record__mmap_read

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Commit-ID:  2d11c65071d489e20b3a811167507939dd8c2eac
Gitweb:     http://git.kernel.org/tip/2d11c65071d489e20b3a811167507939dd8c2eac
Author:     Wang Nan <wangnan0@huawei.com>
AuthorDate: Mon, 23 May 2016 07:13:39 +0000
Committer:  Arnaldo Carvalho de Melo <acme@redhat.com>
CommitDate: Mon, 23 May 2016 18:22:46 -0300

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>
---
 tools/perf/builtin-record.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
index f3679c4..f302cc9 100644
--- 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];

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[PATCH v3 00/11] perf tools: Support overwritable ring buffer Wang Nan <wangnan0@huawei.com> - 2016-05-23 09:20 +0200
  [PATCH v3 11/11] perf tools: Check write_backward during evlist config Wang Nan <wangnan0@huawei.com> - 2016-05-23 09:20 +0200
  [PATCH v3 10/11] perf tools: Don't warn about out of order event if write_backward is used Wang Nan <wangnan0@huawei.com> - 2016-05-23 09:20 +0200
  [PATCH v3 03/11] perf record: Rename variable to make code clear Wang Nan <wangnan0@huawei.com> - 2016-05-23 09:20 +0200
    [tip:perf/urgent] perf record: Rename variable to make code clear tip-bot for Wang Nan <tipbot@zytor.com> - 2016-05-24 07:50 +0200
  [PATCH v3 09/11] perf record: Toggle overwrite ring buffer for reading Wang Nan <wangnan0@huawei.com> - 2016-05-23 09:20 +0200
  [PATCH v3 02/11] perf record: Prevent reading invalid data in record__mmap_read Wang Nan <wangnan0@huawei.com> - 2016-05-23 09:20 +0200
    [tip:perf/urgent] perf record: Prevent reading invalid data in  record__mmap_read tip-bot for Wang Nan <tipbot@zytor.com> - 2016-05-24 07:50 +0200
  [PATCH v3 07/11] perf tools: Enable overwrite settings Wang Nan <wangnan0@huawei.com> - 2016-05-23 09:20 +0200
  [PATCH v3 08/11] perf record: Introduce rec->overwrite_evlist for overwritable events Wang Nan <wangnan0@huawei.com> - 2016-05-23 09:20 +0200

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