Commit-ID: 1144182a8757f2a1f909f0c592898aaaf80884fc
Gitweb: http://git.kernel.org/tip/1144182a8757f2a1f909f0c592898aaaf80884fc
Author: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
AuthorDate: Wed, 6 Oct 2010 17:15:35 -0700
Committer: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
CommitDate: Thu, 7 Oct 2010 10:02:28 -0700
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@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
---
net/core/sock.c | 5 ++++-
1 files changed, 4 insertions(+), 1 deletions(-)
diff --git a/net/core/sock.c b/net/core/sock.c
index ef30e9d..7d99e13 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;
}
--
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