tools/cgget: fix segfault in get_cv_value()

cgget segfaulted on v2.0.2 branch, with:
cgget: cannot find controller 'incal' in group '016cgget'
Fatal error: glibc detected an invalid stdio handle
Aborted (core dumped)

It was caught by ftests/016-cgget-invalid_options.py on Ubuntu 22.04, a
simple reproducer on the v2.0.2 branch:
$ sudo ./src/tools/cgget -n -v -r invalid.setting 016cgget
assuming 016cgget cgroup exists.

It is due to the invalid controller name passed to the
cgroup_read_value_begin(), which returns failure and callee
get_cv_value() in the error clean up path, does a fclose(handle).
If (handle != NULL) succeeds because its uninitialized and has some
garbage value. Fix this by initializing the handle to NULL.

Signed-off-by: Kamalesh Babulal <kamalesh.babulal@oracle.com>
Signed-off-by: Tom Hromatka <tom.hromatka@oracle.com>

diff --git a/src/tools/cgget.c b/src/tools/cgget.c
index dd9a7b6ae71014e0cf6bdeb465d3255c5bc40a3e..33928c37333f78a6aa55167f267b5520e3f31cb3 100644 (file)
--- a/src/tools/cgget.c
+++ b/src/tools/cgget.c
@@ -458,8 +458,8 @@ static int get_cv_value(struct control_value * const cv, const char * const cg_n
                        const char * const controller_name)
 {
        bool is_multiline = false;
+       void *tmp, *handle = NULL;
        char tmp_line[LL_MAX];
-       void *handle, *tmp;
        int ret;
 
        ret = cgroup_read_value_begin(controller_name, cg_name, cv->name, &handle, tmp_line,