On Fri, Oct 05, 2012 at 07:52:15PM -0300, Cristian RodrÃguez wrote:
> Hi:
> I am getting this in the current linus tree.
>
> [ 0.408781] ===============================
> [ 0.408783] [ INFO: suspicious RCU usage. ]
> [ 0.408786] 3.6.0-canneverbe-07124-g5f3d2f2 #18 Not tainted
> [ 0.408789] -------------------------------
> [ 0.408791] include/linux/cgroup.h:566 suspicious
> rcu_dereference_check() usage!
> [ 0.408795]
> [ 0.408795] other info that might help us debug this:
> [ 0.408795]
> [ 0.408799]
> [ 0.408799] rcu_scheduler_active = 1, debug_locks = 0
> [ 0.408802] 2 locks held by kdevtmpfs/49:
> [ 0.408804] #0: (sb_writers){.+.+.+}, at: [<ffffffff8119a2ef>]
> mnt_want_write+0x1f/0x50
> [ 0.408814] #1: (&sb->s_type->i_mutex_key#3/1){+.+.+.}, at:
> [<ffffffff811857cf>] kern_path_create+0x7f/0x170
> [ 0.408822]
> [ 0.408822] stack backtrace:
> [ 0.408825] Pid: 49, comm: kdevtmpfs Not tainted
> 3.6.0-canneverbe-07124-g5f3d2f2 #18
> [ 0.408829] Call Trace:
> [ 0.408834] [<ffffffff8109fabd>] lockdep_rcu_suspicious+0xfd/0x130
> [ 0.408838] [<ffffffff812a876d>] devcgroup_inode_mknod+0x18d/0x230
> [ 0.408843] [<ffffffff8126f923>] ? security_capable+0x13/0x20
> [ 0.408848] [<ffffffff8104a06f>] ? ns_capable+0x3f/0x80
> [ 0.408851] [<ffffffff81186c09>] vfs_mknod+0x79/0x140
> [ 0.408856] [<ffffffff813a6df2>] handle_create.isra.2+0x72/0x200
> [ 0.408860] [<ffffffff813a702c>] ? devtmpfsd+0xac/0x140
> [ 0.408863] [<ffffffff813a7094>] devtmpfsd+0x114/0x140
> [ 0.408867] [<ffffffff813a6f80>] ? handle_create.isra.2+0x200/0x200
> [ 0.408871] [<ffffffff81064de6>] kthread+0xd6/0xe0
> [ 0.408877] [<ffffffff81578cb4>] kernel_thread_helper+0x4/0x10
> [ 0.408881] [<ffffffff8156f85c>] ? retint_restore_args+0xe/0xe
> [ 0.408885] [<ffffffff81064d10>] ? flush_kthread_work+0x190/0x190
> [ 0.408889] [<ffffffff81578cb0>] ? gs_change+0xb/0xb
>
>
> Hope someone can take a look at it.
It looks to me like commit #ad676077 (device_cgroup: convert device_cgroup
internally to policy + exceptions) removed a needed rcu_read_lock().
See below for an untested patch restoring rcu_read_lock().
Thanx, Paul
------------------------------------------------------------------------
device_cgroup: Restore rcu_read_lock() protection to devcgroup_inode_mknod()
Commit ad676077 (device_cgroup: convert device_cgroup internally to
policy + exceptions) restructured devcgroup_inode_mknod(), removing
rcu_read_lock() in the process. However, RCU read-side protection
is required by the call to task_devcgroup(), so this commit restores
the rcu_read_lock() and rcu_read_unlock().
Signed-off-by: Paul E. McKenney <paul...@linux.vnet.ibm.com>
diff --git a/security/device_cgroup.c b/security/device_cgroup.c
index 44dfc41..c686110 100644
--- a/security/device_cgroup.c
+++ b/security/device_cgroup.c
@@ -576,9 +576,12 @@ int __devcgroup_inode_permission(struct inode *inode, int
mask)
int devcgroup_inode_mknod(int mode, dev_t dev)
{
- struct dev_cgroup *dev_cgroup = task_devcgroup(current);
+ struct dev_cgroup *dev_cgroup;
+ int ret;
short type;
+ rcu_read_lock();
+ dev_cgroup = task_devcgroup(current);
if (!S_ISBLK(mode) && !S_ISCHR(mode))
return 0;
@@ -587,7 +590,9 @@ int devcgroup_inode_mknod(int mode, dev_t dev)
else
type = DEV_CHAR;
- return __devcgroup_check_permission(dev_cgroup, type, MAJOR(dev),
+ ret = __devcgroup_check_permission(dev_cgroup, type, MAJOR(dev),
MINOR(dev), ACC_MKNOD);
+ rcu_read_unlock();
+ return ret;
}
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
