cgroup: fix uninitialised iterator in for_each_subsys_which

Fix the fact that @ssid is uninitialised in the case where
CGROUP_SUBSYS_COUNT = 0 by setting ssid to 0.

Fixes: cb4a31675270 ("cgroup: use bitmask to filter for_each_subsys")
Signed-off-by: Aleksa Sarai <cyphar@cyphar.com>
Signed-off-by: Tejun Heo <tj@kernel.org>

diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index 6d6d3c75209645dd75f2239f580234127aabdde9..12b580f4338e0dfe5456e35a85cf63c604ade6f8 100644 (file)
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -424,7 +424,7 @@ static int notify_on_release(const struct cgroup *cgrp)
  */
 #define for_each_subsys_which(ss, ssid, ss_maskp)                      \
        if (!CGROUP_SUBSYS_COUNT) /* to avoid spurious gcc warning */   \
-               ;                                                       \
+               (ssid) = 0;                                             \
        else                                                            \
                for_each_set_bit(ssid, ss_maskp, CGROUP_SUBSYS_COUNT)   \
                        if (((ss) = cgroup_subsys[ssid]) && false)      \