device_cgroup: fix RCU imbalance in error case

commit 0fcc4c8c044e117ac126ab6df4138ea9a67fa2a9 upstream.

When dev_exception_add() returns an error (due to a failed memory
allocation), make sure that we move the RCU preemption count back to where
it was before we were called. We dropped the RCU read lock inside the loop
body, so we can't just "break".

sparse complains about this, too:

$ make -s C=2 security/device_cgroup.o
./include/linux/rcupdate.h:647:9: warning: context imbalance in
'propagate_exception' - unexpected unlock

Fixes: d591fb56618f ("device_cgroup: simplify cgroup tree walk in propagate_exception()")
Cc: stable@vger.kernel.org
Signed-off-by: Jann Horn <jannh@google.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/security/device_cgroup.c b/security/device_cgroup.c
index 188c1d26393b56bfd13814e7834119a440410114..dc071be564f962148355761cad071539aa7704ba 100644 (file)
--- a/security/device_cgroup.c
+++ b/security/device_cgroup.c
@@ -568,7 +568,7 @@ static int propagate_exception(struct dev_cgroup *devcg_root,
                    devcg->behavior == DEVCG_DEFAULT_ALLOW) {
                        rc = dev_exception_add(devcg, ex);
                        if (rc)
-                               break;
+                               return rc;
                } else {
                        /*
                         * in the other possible cases: