From 35d9b0c906ad92d32a0b8db5daa6fabfcc2f068d Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Sun, 5 Dec 2010 02:03:26 +0000 Subject: [PATCH] llc: fix a device refcount imbalance MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit Le dimanche 05 décembre 2010 à 12:23 +0100, Eric Dumazet a écrit : > Le dimanche 05 décembre 2010 à 09:19 +0100, Eric Dumazet a écrit : > > > Hmm.. > > > > If somebody can explain why RTNL is held in arp_ioctl() (and therefore > > in arp_req_delete()), we might first remove RTNL use in arp_ioctl() so > > that your patch can be applied. > > > > Right now it is not good, because RTNL wont be necessarly held when you > > are going to call arp_invalidate() ? > > While doing this analysis, I found a refcount bug in llc, I'll send a > patch for net-2.6 Oh well, of course I must first fix the bug in net-2.6, and wait David pull the fix in net-next-2.6 before sending this rcu conversion. Note: this patch should be sent to stable teams (2.6.34 and up) [PATCH net-2.6] llc: fix a device refcount imbalance commit abf9d537fea225 (llc: add support for SO_BINDTODEVICE) added one refcount imbalance in llc_ui_bind(), because dev_getbyhwaddr() doesnt take a reference on device, while dev_get_by_index() does. Fix this using RCU locking. And since an RCU conversion will be done for 2.6.38 for dev_getbyhwaddr(), put the rcu_read_lock/unlock exactly at their final place. Signed-off-by: Eric Dumazet Cc: stable@kernel.org Cc: Octavian Purdila Signed-off-by: David S. Miller --- net/llc/af_llc.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/net/llc/af_llc.c b/net/llc/af_llc.c index 582612998211..e35dbe55f520 100644 --- a/net/llc/af_llc.c +++ b/net/llc/af_llc.c @@ -317,8 +317,9 @@ static int llc_ui_bind(struct socket *sock, struct sockaddr *uaddr, int addrlen) goto out; rc = -ENODEV; rtnl_lock(); + rcu_read_lock(); if (sk->sk_bound_dev_if) { - llc->dev = dev_get_by_index(&init_net, sk->sk_bound_dev_if); + llc->dev = dev_get_by_index_rcu(&init_net, sk->sk_bound_dev_if); if (llc->dev) { if (!addr->sllc_arphrd) addr->sllc_arphrd = llc->dev->type; @@ -329,13 +330,13 @@ static int llc_ui_bind(struct socket *sock, struct sockaddr *uaddr, int addrlen) !llc_mac_match(addr->sllc_mac, llc->dev->dev_addr)) { rc = -EINVAL; - dev_put(llc->dev); llc->dev = NULL; } } } else llc->dev = dev_getbyhwaddr(&init_net, addr->sllc_arphrd, addr->sllc_mac); + rcu_read_unlock(); rtnl_unlock(); if (!llc->dev) goto out; -- 2.20.1