From: Jiri Slaby <jslaby@suse.cz>
To: akpm@linux-foundation.org
Cc: jirislaby@gmail.com, linux-kernel@vger.kernel.org,
Jiri Slaby <jslaby@suse.cz>,
aris@redhat.com, Tejun Heo <tj@kernel.org>,
lizefan@huawei.com
Subject: [PATCH] cgroup: fix invalid rcu dereference
Date: Fri, 14 Sep 2012 11:40:12 +0200 [thread overview]
Message-ID: <1347615612-11450-1-git-send-email-jslaby@suse.cz> (raw)
In-Reply-To: <5052F78A.7010007@suse.cz>
Commit "device_cgroup: convert device_cgroup internally to policy +
exceptions" removed rcu locks which are needed in task_devcgroup
called in this chain: devcgroup_inode_mknod OR
__devcgroup_inode_permission -> __devcgroup_inode_permission ->
task_devcgroup -> task_subsys_state -> task_subsys_state_check.
Change the code so that task_devcgroup is safely called with rcu read
lock held.
===============================
[ INFO: suspicious RCU usage. ]
3.6.0-rc5-next-20120913+ #42 Not tainted
-------------------------------
/home/latest/linux/include/linux/cgroup.h:553 suspicious
rcu_dereference_check() usage!
other info that might help us debug this:
rcu_scheduler_active = 1, debug_locks = 0
2 locks held by kdevtmpfs/23:
#0: (sb_writers){.+.+.+}, at: [<ffffffff8116873f>]
mnt_want_write+0x1f/0x50
#1: (&sb->s_type->i_mutex_key#3/1){+.+.+.}, at: [<ffffffff811558af>]
kern_path_create+0x7f/0x170
stack backtrace:
Pid: 23, comm: kdevtmpfs Not tainted 3.6.0-rc5-next-20120913+ #42
Call Trace:
[<ffffffff810c638d>] lockdep_rcu_suspicious+0xfd/0x130
[<ffffffff8121541d>] devcgroup_inode_mknod+0x19d/0x240
[<ffffffff8107bf54>] ? ns_capable+0x44/0x80
[<ffffffff81156b21>] vfs_mknod+0x71/0xf0
[<ffffffff813a8332>] handle_create.isra.2+0x72/0x200
[<ffffffff813a85d4>] devtmpfsd+0x114/0x140
[<ffffffff813a84c0>] ? handle_create.isra.2+0x200/0x200
[<ffffffff81093ad6>] kthread+0xd6/0xe0
[<ffffffff81654f24>] kernel_thread_helper+0x4/0x10
[<ffffffff8165369d>] ? retint_restore_args+0xe/0xe
[<ffffffff81093a00>] ? kthread_create_on_node+0x140/0x140
[<ffffffff81654f20>] ? gs_change+0xb/0xb
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Cc: aris@redhat.com
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Tejun Heo <tj@kernel.org>
Cc: lizefan@huawei.com
---
And this should fix it.
security/device_cgroup.c | 15 +++++++--------
1 file changed, 7 insertions(+), 8 deletions(-)
diff --git a/security/device_cgroup.c b/security/device_cgroup.c
index 8d21ded..2178886 100644
--- a/security/device_cgroup.c
+++ b/security/device_cgroup.c
@@ -524,10 +524,10 @@ struct cgroup_subsys devices_subsys = {
*
* returns 0 on success, -EPERM case the operation is not permitted
*/
-static int __devcgroup_check_permission(struct dev_cgroup *dev_cgroup,
- short type, u32 major, u32 minor,
+static int __devcgroup_check_permission(short type, u32 major, u32 minor,
short access)
{
+ struct dev_cgroup *dev_cgroup;
struct dev_exception_item ex;
int rc;
@@ -538,6 +538,7 @@ static int __devcgroup_check_permission(struct dev_cgroup *dev_cgroup,
ex.access = access;
rcu_read_lock();
+ dev_cgroup = task_devcgroup(current);
rc = may_access(dev_cgroup, &ex);
rcu_read_unlock();
@@ -549,7 +550,6 @@ static int __devcgroup_check_permission(struct dev_cgroup *dev_cgroup,
int __devcgroup_inode_permission(struct inode *inode, int mask)
{
- struct dev_cgroup *dev_cgroup = task_devcgroup(current);
short type, access = 0;
if (S_ISBLK(inode->i_mode))
@@ -561,13 +561,12 @@ int __devcgroup_inode_permission(struct inode *inode, int mask)
if (mask & MAY_READ)
access |= ACC_READ;
- return __devcgroup_check_permission(dev_cgroup, type, imajor(inode),
- iminor(inode), access);
+ return __devcgroup_check_permission(type, imajor(inode), iminor(inode),
+ access);
}
int devcgroup_inode_mknod(int mode, dev_t dev)
{
- struct dev_cgroup *dev_cgroup = task_devcgroup(current);
short type;
if (!S_ISBLK(mode) && !S_ISCHR(mode))
@@ -578,7 +577,7 @@ int devcgroup_inode_mknod(int mode, dev_t dev)
else
type = DEV_CHAR;
- return __devcgroup_check_permission(dev_cgroup, type, MAJOR(dev),
- MINOR(dev), ACC_MKNOD);
+ return __devcgroup_check_permission(type, MAJOR(dev), MINOR(dev),
+ ACC_MKNOD);
}
--
1.7.11.5
next prev parent reply other threads:[~2012-09-14 9:40 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-09-14 9:23 include/linux/cgroup.h:553 suspicious rcu_dereference_check() usage! Jiri Slaby
2012-09-14 9:40 ` Jiri Slaby [this message]
2012-09-14 13:27 ` [PATCH] cgroup: fix invalid rcu dereference Aristeu Rozanski
2012-09-14 17:01 ` Tejun Heo
2012-09-17 1:09 ` Li Zefan
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