[tip:perf/urgent] perf header: Fix divide by zero error if f_header.attr_size==0

[tip-bot for Vince Weaver <tipbot@zytor.com>]

Commit-ID:  7622236ceb167aa3857395f9bdaf871442aa467e
Gitweb:     https://git.kernel.org/tip/7622236ceb167aa3857395f9bdaf871442aa467e
Author:     Vince Weaver <vincent.weaver@maine.edu>
AuthorDate: Tue, 23 Jul 2019 11:06:01 -0400
Committer:  Arnaldo Carvalho de Melo <acme@redhat.com>
CommitDate: Mon, 29 Jul 2019 09:03:43 -0300

perf header: Fix divide by zero error if f_header.attr_size==0

So I have been having lots of trouble with hand-crafted perf.data files
causing segfaults and the like, so I have started fuzzing the perf tool.

First issue found:

If f_header.attr_size is 0 in the perf.data file, then perf will crash
with a divide-by-zero error.

Committer note:

Added a pr_err() to tell the user why the command failed.

Signed-off-by: Vince Weaver <vincent.weaver@maine.edu>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/alpine.DEB.2.21.1907231100440.14532@macbook-air
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
---
 tools/perf/util/header.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/tools/perf/util/header.c b/tools/perf/util/header.c
index 20111f8da5cb..47877f0f6667 100644
--- a/tools/perf/util/header.c
+++ b/tools/perf/util/header.c
@@ -3559,6 +3559,13 @@ int perf_session__read_header(struct perf_session *session)
 			   data->file.path);
 	}
 
+	if (f_header.attr_size == 0) {
+		pr_err("ERROR: The %s file's attr size field is 0 which is unexpected.\n"
+		       "Was the 'perf record' command properly terminated?\n",
+		       data->file.path);
+		return -EINVAL;
+	}
+
 	nr_attrs = f_header.attrs.size / f_header.attr_size;
 	lseek(fd, f_header.attrs.offset, SEEK_SET);