br2684: fix module_put() race

The br2684 code used module_put() during unassignment from vcc with
hope that we have BKL. This assumption is no longer true.

Now owner field in atmvcc is used to move this module_put()
to vcc_destroy_socket().

Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>
Acked-by: Krzysztof Mazur <krzysiek@podlesie.net>

diff --git a/net/atm/br2684.c b/net/atm/br2684.c
index 4de3ae7bc3e26e0a12e4cb5ef4ddb1335779b5f9..6dc383c90262263c73af300eb8f3220d100aad79 100644 (file)
--- a/net/atm/br2684.c
+++ b/net/atm/br2684.c
@@ -69,6 +69,7 @@ struct br2684_vcc {
        void (*old_push)(struct atm_vcc *vcc, struct sk_buff *skb);
        void (*old_pop)(struct atm_vcc *vcc, struct sk_buff *skb);
        void (*old_release_cb)(struct atm_vcc *vcc);
+       struct module *old_owner;
        enum br2684_encaps encaps;
        struct list_head brvccs;
 #ifdef CONFIG_ATM_BR2684_IPFILTER
@@ -414,8 +415,8 @@ static void br2684_close_vcc(struct br2684_vcc *brvcc)
        brvcc->atmvcc->user_back = NULL;        /* what about vcc->recvq ??? */
        brvcc->atmvcc->release_cb = brvcc->old_release_cb;
        brvcc->old_push(brvcc->atmvcc, NULL);   /* pass on the bad news */
+       module_put(brvcc->old_owner);
        kfree(brvcc);
-       module_put(THIS_MODULE);
 }
 
 /* when AAL5 PDU comes in: */
@@ -590,10 +591,12 @@ static int br2684_regvcc(struct atm_vcc *atmvcc, void __user * arg)
        brvcc->old_push = atmvcc->push;
        brvcc->old_pop = atmvcc->pop;
        brvcc->old_release_cb = atmvcc->release_cb;
+       brvcc->old_owner = atmvcc->owner;
        barrier();
        atmvcc->push = br2684_push;
        atmvcc->pop = br2684_pop;
        atmvcc->release_cb = br2684_release_cb;
+       atmvcc->owner = THIS_MODULE;
 
        /* initialize netdev carrier state */
        if (atmvcc->dev->signal == ATM_PHY_SIG_LOST)