From 0fcc4c8c044e117ac126ab6df4138ea9a67fa2a9 Mon Sep 17 00:00:00 2001
From: Jann Horn <jannh@google.com>
Date: Tue, 19 Mar 2019 02:36:59 +0100
Subject: [PATCH] device_cgroup: fix RCU imbalance in error case
Git-commit: 0fcc4c8c044e117ac126ab6df4138ea9a67fa2a9
Patch-mainline: v5.1-rc6
References: bsc#1051510

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>
Acked-by: Takashi Iwai <tiwai@suse.de>

---
 security/device_cgroup.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/security/device_cgroup.c b/security/device_cgroup.c
index cd97929fac66..dc28914fa72e 100644
--- a/security/device_cgroup.c
+++ b/security/device_cgroup.c
@@ -560,7 +560,7 @@ 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:
-- 
2.16.4