linux-kernel - [PATCH] device_cgroup: don't grab mutex in rcu callback

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [day] [month] [year] [list]

Message-Id: <1358964019-12433-1-git-send-email-jerry.snitselaar@oracle.com>
Date:	Wed, 23 Jan 2013 11:00:19 -0700
From:	Jerry Snitselaar <jerry.snitselaar@...cle.com>
To:	jmorris@...ei.org
Cc:	tj@...nel.org, linux-kernel@...r.kernel.org
Subject: [PATCH] device_cgroup: don't grab mutex in rcu callback

commit 103a197 "security/device_cgroup: lock assert fails in
dev_exception_clean()" grabs devcgroup_mutex to fix assert failure,
but mutex can't be grabbed in rcu callback. Since there shouldn't be
any other references when css_free is called, mutex isn't needed for
list cleanup in devcgroup_css_free().

Signed-off-by: Jerry Snitselaar <jerry.snitselaar@...cle.com>
Acked-by: Tejun Heo <tj@...nel.org>
---
 security/device_cgroup.c | 21 ++++++++++++---------
 1 file changed, 12 insertions(+), 9 deletions(-)

diff --git a/security/device_cgroup.c b/security/device_cgroup.c
index d794abc..1c69e38 100644
--- a/security/device_cgroup.c
+++ b/security/device_cgroup.c
@@ -159,6 +159,16 @@ static void dev_exception_rm(struct dev_cgroup *dev_cgroup,
 	}
 }
 
+static void __dev_exception_clean(struct dev_cgroup *dev_cgroup)
+{
+	struct dev_exception_item *ex, *tmp;
+
+	list_for_each_entry_safe(ex, tmp, &dev_cgroup->exceptions, list) {
+		list_del_rcu(&ex->list);
+		kfree_rcu(ex, rcu);
+	}
+}
+
 /**
  * dev_exception_clean - frees all entries of the exception list
  * @dev_cgroup: dev_cgroup with the exception list to be cleaned
@@ -167,14 +177,9 @@ static void dev_exception_rm(struct dev_cgroup *dev_cgroup,
  */
 static void dev_exception_clean(struct dev_cgroup *dev_cgroup)
 {
-	struct dev_exception_item *ex, *tmp;
-
 	lockdep_assert_held(&devcgroup_mutex);
 
-	list_for_each_entry_safe(ex, tmp, &dev_cgroup->exceptions, list) {
-		list_del_rcu(&ex->list);
-		kfree_rcu(ex, rcu);
-	}
+	__dev_exception_clean(dev_cgroup);
 }
 
 /*
@@ -215,9 +220,7 @@ static void devcgroup_css_free(struct cgroup *cgroup)
 	struct dev_cgroup *dev_cgroup;
 
 	dev_cgroup = cgroup_to_devcgroup(cgroup);
-	mutex_lock(&devcgroup_mutex);
-	dev_exception_clean(dev_cgroup);
-	mutex_unlock(&devcgroup_mutex);
+	__dev_exception_clean(dev_cgroup);
 	kfree(dev_cgroup);
 }
 
-- 
1.8.1.1.293.gfe73786

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/