perf machine: Null-terminate version char array upon fgets(/proc/version) error

If fgets() fails due to any other error besides end-of-file, the version
char array may not even be null-terminated.

Signed-off-by: Donald Yandt <donald.yandt@gmail.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Avi Kivity <avi@scylladb.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Yanmin Zhang <yanmin_zhang@linux.intel.com>
Fixes: cb30dcad8c90 ("perf: 'perf kvm' tool for monitoring guest performance from host")
Link: http://lkml.kernel.org/r/20190514110100.22019-1-donald.yandt@gmail.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

diff --git a/tools/perf/util/machine.c b/tools/perf/util/machine.c
index 3c520baa198cfcc49276ca77a8f8c12d058bec4d..28a9541c48359cad6a52ea4e8609cfba3e2be023 100644 (file)
--- a/tools/perf/util/machine.c
+++ b/tools/perf/util/machine.c
@@ -1234,8 +1234,9 @@ static char *get_kernel_version(const char *root_dir)
        if (!file)
                return NULL;
 
-       version[0] = '\0';
        tmp = fgets(version, sizeof(version), file);
+       if (!tmp)
+               *version = '\0';
        fclose(file);
 
        name = strstr(version, prefix);