From: Jann Horn <jannh@google.com>
Date: Tue, 19 Mar 2019 01:36:59 +0000 (+0100)
Subject: device_cgroup: fix RCU imbalance in error case
X-Git-Tag: v3.16.72~130
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=198f512652c375a22744e86dda97b46b5854e04f;p=thirdparty%2Fkernel%2Fstable.git

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()")
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: Ben Hutchings <ben@decadent.org.uk>
---

diff --git a/security/device_cgroup.c b/security/device_cgroup.c
index d9d69e6930edf..8fee5f7be4f17 100644
--- 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: