Linux v4.2-4282-gae982073095a

1 files changed, 71 insertions, 0 deletions

diff --git a/security-device_cgroup-fix-RCU-lockdep-splat.patch b/security-device_cgroup-fix-RCU-lockdep-splat.patch
new file mode 100644
index 000000000..2de959ee9
--- /dev/null
+++ b/security-device_cgroup-fix-RCU-lockdep-splat.patch
@@ -0,0 +1,71 @@
+From 28e1b4326abcc66839c6e21dd410fe983ee83fb3 Mon Sep 17 00:00:00 2001
+From: Felipe Balbi <balbi@ti.com>
+Date: Wed, 2 Sep 2015 08:12:28 -0500
+Subject: [PATCH] security: device_cgroup: fix RCU lockdep splat
+
+while booting AM437x device, the following splat
+triggered:
+
+[   12.005238] ===============================
+[   12.009749] [ INFO: suspicious RCU usage. ]
+[   12.014116] 4.2.0-next-20150831 #1154 Not tainted
+[   12.019050] -------------------------------
+[   12.023408] security/device_cgroup.c:405 device_cgroup:verify_new_ex called without proper synchronization!
+[   12.033576] other info that might help us debug this:
+
+[   12.041942] rcu_scheduler_active = 1, debug_locks = 0
+[   12.048796] 4 locks held by systemd/1:
+[   12.052700]  #0:  (sb_writers#7){.+.+.+}, at: [<c017af84>] __sb_start_write+0x8c/0xb0
+[   12.060954]  #1:  (&of->mutex){+.+.+.}, at: [<c01f1600>] kernfs_fop_write+0x50/0x1b8
+[   12.069085]  #2:  (s_active#30){++++.+}, at: [<c01f1608>] kernfs_fop_write+0x58/0x1b8
+[   12.077310]  #3:  (devcgroup_mutex){+.+...}, at: [<c0317bfc>] devcgroup_access_write+0x20/0x658
+[   12.086575] stack backtrace:
+[   12.091124] CPU: 0 PID: 1 Comm: systemd Not tainted 4.2.0-next-20150831 #1154
+[   12.098609] Hardware name: Generic AM43 (Flattened Device Tree)
+[   12.104807] [<c001770c>] (unwind_backtrace) from [<c0013a58>] (show_stack+0x10/0x14)
+[   12.112924] [<c0013a58>] (show_stack) from [<c034f014>] (dump_stack+0x84/0x9c)
+[   12.120491] [<c034f014>] (dump_stack) from [<c0317a04>] (verify_new_ex+0xc4/0xdc)
+[   12.128326] [<c0317a04>] (verify_new_ex) from [<c0317f50>] (devcgroup_access_write+0x374/0x658)
+[   12.137426] [<c0317f50>] (devcgroup_access_write) from [<c00d2800>] (cgroup_file_write+0x28/0x1bc)
+[   12.146796] [<c00d2800>] (cgroup_file_write) from [<c01f1670>] (kernfs_fop_write+0xc0/0x1b8)
+[   12.155620] [<c01f1670>] (kernfs_fop_write) from [<c0177c94>] (__vfs_write+0x1c/0xd8)
+[   12.163783] [<c0177c94>] (__vfs_write) from [<c0178594>] (vfs_write+0x90/0x16c)
+[   12.171426] [<c0178594>] (vfs_write) from [<c0178db4>] (SyS_write+0x44/0x9c)
+[   12.178806] [<c0178db4>] (SyS_write) from [<c000f680>] (ret_fast_syscall+0x0/0x1c)
+
+Fix it by making sure rcu_read_lock() is held
+around calls to parent_has_perm().
+
+Signed-off-by: Felipe Balbi <balbi@ti.com>
+---
+ security/device_cgroup.c | 7 ++++++-
+ 1 file changed, 6 insertions(+), 1 deletion(-)
+
+diff --git a/security/device_cgroup.c b/security/device_cgroup.c
+index 73455089feef..dd77ed206fa4 100644
+--- a/security/device_cgroup.c
++++ b/security/device_cgroup.c
+@@ -608,6 +608,7 @@ static int devcgroup_update_access(struct dev_cgroup *devcgroup,
+ 	int count, rc = 0;
+ 	struct dev_exception_item ex;
+ 	struct dev_cgroup *parent = css_to_devcgroup(devcgroup->css.parent);
++	int ret;
+ 
+ 	if (!capable(CAP_SYS_ADMIN))
+ 		return -EPERM;
+@@ -734,7 +735,11 @@ static int devcgroup_update_access(struct dev_cgroup *devcgroup,
+ 			break;
+ 		}
+ 
+-		if (!parent_has_perm(devcgroup, &ex))
++		rcu_read_lock();
++		ret = parent_has_perm(devcgroup, &ex);
++		rcu_read_unlock();
++
++		if (!ret)
+ 			return -EPERM;
+ 		rc = dev_exception_add(devcgroup, &ex);
+ 		break;
+-- 
+2.4.3
+