From: Niels Dossche dossche.niels@gmail.com
[ Upstream commit 51454ea42c1ab4e0c2828bb0d4d53957976980de ]
idev->addr_list needs to be protected by idev->lock. However, it is not always possible to do so while iterating and performing actions on inet6_ifaddr instances. For example, multiple functions (like addrconf_{join,leave}_anycast) eventually call down to other functions that acquire the idev->lock. The current code temporarily unlocked the idev->lock during the loops, which can cause race conditions. Moving the locks up is also not an appropriate solution as the ordering of lock acquisition will be inconsistent with for example mc_lock.
This solution adds an additional field to inet6_ifaddr that is used to temporarily add the instances to a temporary list while holding idev->lock. The temporary list can then be traversed without holding idev->lock. This change was done in two places. In addrconf_ifdown, the list_for_each_entry_safe variant of the list loop is also no longer necessary as there is no deletion within that specific loop.
Suggested-by: Paolo Abeni pabeni@redhat.com Signed-off-by: Niels Dossche dossche.niels@gmail.com Acked-by: Paolo Abeni pabeni@redhat.com Link: https://lore.kernel.org/r/20220403231523.45843-1-dossche.niels@gmail.com Signed-off-by: Jakub Kicinski kuba@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- include/net/if_inet6.h | 8 ++++++++ net/ipv6/addrconf.c | 30 ++++++++++++++++++++++++------ 2 files changed, 32 insertions(+), 6 deletions(-)
diff --git a/include/net/if_inet6.h b/include/net/if_inet6.h index d7578cf49c3a..3953003b0490 100644 --- a/include/net/if_inet6.h +++ b/include/net/if_inet6.h @@ -69,6 +69,14 @@ struct inet6_ifaddr {
struct hlist_node addr_lst; struct list_head if_list; + /* + * Used to safely traverse idev->addr_list in process context + * if the idev->lock needed to protect idev->addr_list cannot be held. + * In that case, add the items to this list temporarily and iterate + * without holding idev->lock. + * See addrconf_ifdown and dev_forward_change. + */ + struct list_head if_list_aux;
struct list_head tmp_list; struct inet6_ifaddr *ifpub; diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c index 9d8b791f63ef..a8db1efccbf5 100644 --- a/net/ipv6/addrconf.c +++ b/net/ipv6/addrconf.c @@ -739,6 +739,7 @@ static void dev_forward_change(struct inet6_dev *idev) { struct net_device *dev; struct inet6_ifaddr *ifa; + LIST_HEAD(tmp_addr_list);
if (!idev) return; @@ -757,14 +758,24 @@ static void dev_forward_change(struct inet6_dev *idev) } }
+ read_lock_bh(&idev->lock); list_for_each_entry(ifa, &idev->addr_list, if_list) { if (ifa->flags&IFA_F_TENTATIVE) continue; + list_add_tail(&ifa->if_list_aux, &tmp_addr_list); + } + read_unlock_bh(&idev->lock); + + while (!list_empty(&tmp_addr_list)) { + ifa = list_first_entry(&tmp_addr_list, + struct inet6_ifaddr, if_list_aux); + list_del(&ifa->if_list_aux); if (idev->cnf.forwarding) addrconf_join_anycast(ifa); else addrconf_leave_anycast(ifa); } + inet6_netconf_notify_devconf(dev_net(dev), RTM_NEWNETCONF, NETCONFA_FORWARDING, dev->ifindex, &idev->cnf); @@ -3658,7 +3669,8 @@ static int addrconf_ifdown(struct net_device *dev, int how) unsigned long event = how ? NETDEV_UNREGISTER : NETDEV_DOWN; struct net *net = dev_net(dev); struct inet6_dev *idev; - struct inet6_ifaddr *ifa, *tmp; + struct inet6_ifaddr *ifa; + LIST_HEAD(tmp_addr_list); bool keep_addr = false; int state, i;
@@ -3746,16 +3758,23 @@ static int addrconf_ifdown(struct net_device *dev, int how) write_lock_bh(&idev->lock); }
- list_for_each_entry_safe(ifa, tmp, &idev->addr_list, if_list) { + list_for_each_entry(ifa, &idev->addr_list, if_list) + list_add_tail(&ifa->if_list_aux, &tmp_addr_list); + write_unlock_bh(&idev->lock); + + while (!list_empty(&tmp_addr_list)) { struct fib6_info *rt = NULL; bool keep;
+ ifa = list_first_entry(&tmp_addr_list, + struct inet6_ifaddr, if_list_aux); + list_del(&ifa->if_list_aux); + addrconf_del_dad_work(ifa);
keep = keep_addr && (ifa->flags & IFA_F_PERMANENT) && !addr_is_local(&ifa->addr);
- write_unlock_bh(&idev->lock); spin_lock_bh(&ifa->lock);
if (keep) { @@ -3786,15 +3805,14 @@ static int addrconf_ifdown(struct net_device *dev, int how) addrconf_leave_solict(ifa->idev, &ifa->addr); }
- write_lock_bh(&idev->lock); if (!keep) { + write_lock_bh(&idev->lock); list_del_rcu(&ifa->if_list); + write_unlock_bh(&idev->lock); in6_ifa_put(ifa); } }
- write_unlock_bh(&idev->lock); - /* Step 5: Discard anycast and multicast list */ if (how) { ipv6_ac_destroy_dev(idev);