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authorPaul E. McKenney <paulmck@linux.vnet.ibm.com>2010-10-06 17:15:35 -0700
committerPaul E. McKenney <paulmck@linux.vnet.ibm.com>2010-10-07 10:02:28 -0700
commit1144182a8757f2a1f909f0c592898aaaf80884fc (patch)
tree61bec9226c6f132f3c4c4518e688facb3d9e8b7a /net
parent556ef63255f1a6f82910a637c4164dbf7d3d1af2 (diff)
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net: suppress RCU lockdep false positive in sock_update_classid
> =================================================== > [ INFO: suspicious rcu_dereference_check() usage. ] > --------------------------------------------------- > include/linux/cgroup.h:542 invoked rcu_dereference_check() without protection! > > other info that might help us debug this: > > > rcu_scheduler_active = 1, debug_locks = 0 > 1 lock held by swapper/1: > #0: (net_mutex){+.+.+.}, at: [<ffffffff813e9010>] > register_pernet_subsys+0x1f/0x47 > > stack backtrace: > Pid: 1, comm: swapper Not tainted 2.6.35.4-28.fc14.x86_64 #1 > Call Trace: > [<ffffffff8107bd3a>] lockdep_rcu_dereference+0xaa/0xb3 > [<ffffffff813e04b9>] sock_update_classid+0x7c/0xa2 > [<ffffffff813e054a>] sk_alloc+0x6b/0x77 > [<ffffffff8140b281>] __netlink_create+0x37/0xab > [<ffffffff813f941c>] ? rtnetlink_rcv+0x0/0x2d > [<ffffffff8140cee1>] netlink_kernel_create+0x74/0x19d > [<ffffffff8149c3ca>] ? __mutex_lock_common+0x339/0x35b > [<ffffffff813f7e9c>] rtnetlink_net_init+0x2e/0x48 > [<ffffffff813e8d7a>] ops_init+0xe9/0xff > [<ffffffff813e8f0d>] register_pernet_operations+0xab/0x130 > [<ffffffff813e901f>] register_pernet_subsys+0x2e/0x47 > [<ffffffff81db7bca>] rtnetlink_init+0x53/0x102 > [<ffffffff81db835c>] netlink_proto_init+0x126/0x143 > [<ffffffff81db8236>] ? netlink_proto_init+0x0/0x143 > [<ffffffff810021b8>] do_one_initcall+0x72/0x186 > [<ffffffff81d78ebc>] kernel_init+0x23b/0x2c9 > [<ffffffff8100aae4>] kernel_thread_helper+0x4/0x10 > [<ffffffff8149e2d0>] ? restore_args+0x0/0x30 > [<ffffffff81d78c81>] ? kernel_init+0x0/0x2c9 > [<ffffffff8100aae0>] ? kernel_thread_helper+0x0/0x10 The sock_update_classid() function calls task_cls_classid(current), but the calling task cannot go away, so there is no danger of the associated structures disappearing. Insert an RCU read-side critical section to suppress the false positive. Reported-by: Subrata Modak <subrata@linux.vnet.ibm.com> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Diffstat (limited to 'net')
-rw-r--r--net/core/sock.c5
1 files changed, 4 insertions, 1 deletions
diff --git a/net/core/sock.c b/net/core/sock.c
index ef30e9d286e..7d99e13148e 100644
--- a/net/core/sock.c
+++ b/net/core/sock.c
@@ -1078,8 +1078,11 @@ static void sk_prot_free(struct proto *prot, struct sock *sk)
#ifdef CONFIG_CGROUPS
void sock_update_classid(struct sock *sk)
{
- u32 classid = task_cls_classid(current);
+ u32 classid;
+ rcu_read_lock(); /* doing current task, which cannot vanish. */
+ classid = task_cls_classid(current);
+ rcu_read_unlock();
if (classid && classid != sk->sk_classid)
sk->sk_classid = classid;
}