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

Changes from v1-3:
 * close file, then return NULL instead of null-terminating version char array

Fixes: a1645ce12adb ("perf: 'perf kvm' tool for monitoring guest performance 
from host")
Signed-off-by: Donald Yandt <donald.ya...@gmail.com>
---
 tools/perf/util/machine.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/tools/perf/util/machine.c b/tools/perf/util/machine.c
index 3c520baa1..6fd877220 100644
--- a/tools/perf/util/machine.c
+++ b/tools/perf/util/machine.c
@@ -1234,9 +1234,10 @@ static char *get_kernel_version(const char *root_dir)
        if (!file)
                return NULL;

-       version[0] = '\0';
        tmp = fgets(version, sizeof(version), file);
        fclose(file);
+       if (!tmp)
+               return NULL;

        name = strstr(version, prefix);
        if (!name)
--
2.20.1

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