6.6-stable review patch. If anyone has any objections, please let me know.
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From: Eric Dumazet edumazet@google.com
[ Upstream commit 1d55a6974756cf3979efd2cc68bcece611a44053 ]
sock_diag_broadcast_destroy_work() and __sock_diag_cmd() are currently using sock_diag_table_mutex to protect against concurrent sock_diag_handlers[] changes.
This makes inet_diag dump serialized, thus less scalable than legacy /proc files.
It is time to switch to full RCU protection.
Signed-off-by: Eric Dumazet edumazet@google.com Reviewed-by: Guillaume Nault gnault@redhat.com Reviewed-by: Kuniyuki Iwashima kuniyu@amazon.com Reviewed-by: Willem de Bruijn willemb@google.com Signed-off-by: Paolo Abeni pabeni@redhat.com Stable-dep-of: eb02688c5c45 ("ipv6: release nexthop on device removal") Signed-off-by: Sasha Levin sashal@kernel.org --- net/core/sock_diag.c | 73 +++++++++++++++++++++++++------------------- 1 file changed, 42 insertions(+), 31 deletions(-)
diff --git a/net/core/sock_diag.c b/net/core/sock_diag.c index c53b731f2d672..72009e1f4380d 100644 --- a/net/core/sock_diag.c +++ b/net/core/sock_diag.c @@ -16,7 +16,7 @@ #include <linux/inet_diag.h> #include <linux/sock_diag.h>
-static const struct sock_diag_handler *sock_diag_handlers[AF_MAX]; +static const struct sock_diag_handler __rcu *sock_diag_handlers[AF_MAX]; static int (*inet_rcv_compat)(struct sk_buff *skb, struct nlmsghdr *nlh); static DEFINE_MUTEX(sock_diag_table_mutex); static struct workqueue_struct *broadcast_wq; @@ -122,6 +122,24 @@ static size_t sock_diag_nlmsg_size(void) + nla_total_size_64bit(sizeof(struct tcp_info))); /* INET_DIAG_INFO */ }
+static const struct sock_diag_handler *sock_diag_lock_handler(int family) +{ + const struct sock_diag_handler *handler; + + rcu_read_lock(); + handler = rcu_dereference(sock_diag_handlers[family]); + if (handler && !try_module_get(handler->owner)) + handler = NULL; + rcu_read_unlock(); + + return handler; +} + +static void sock_diag_unlock_handler(const struct sock_diag_handler *handler) +{ + module_put(handler->owner); +} + static void sock_diag_broadcast_destroy_work(struct work_struct *work) { struct broadcast_sk *bsk = @@ -138,12 +156,12 @@ static void sock_diag_broadcast_destroy_work(struct work_struct *work) if (!skb) goto out;
- mutex_lock(&sock_diag_table_mutex); - hndl = sock_diag_handlers[sk->sk_family]; - if (hndl && hndl->get_info) - err = hndl->get_info(skb, sk); - mutex_unlock(&sock_diag_table_mutex); - + hndl = sock_diag_lock_handler(sk->sk_family); + if (hndl) { + if (hndl->get_info) + err = hndl->get_info(skb, sk); + sock_diag_unlock_handler(hndl); + } if (!err) nlmsg_multicast(sock_net(sk)->diag_nlsk, skb, 0, group, GFP_KERNEL); @@ -184,33 +202,26 @@ EXPORT_SYMBOL_GPL(sock_diag_unregister_inet_compat);
int sock_diag_register(const struct sock_diag_handler *hndl) { - int err = 0; + int family = hndl->family;
- if (hndl->family >= AF_MAX) + if (family >= AF_MAX) return -EINVAL;
- mutex_lock(&sock_diag_table_mutex); - if (sock_diag_handlers[hndl->family]) - err = -EBUSY; - else - WRITE_ONCE(sock_diag_handlers[hndl->family], hndl); - mutex_unlock(&sock_diag_table_mutex); - - return err; + return !cmpxchg((const struct sock_diag_handler **) + &sock_diag_handlers[family], + NULL, hndl) ? 0 : -EBUSY; } EXPORT_SYMBOL_GPL(sock_diag_register);
-void sock_diag_unregister(const struct sock_diag_handler *hnld) +void sock_diag_unregister(const struct sock_diag_handler *hndl) { - int family = hnld->family; + int family = hndl->family;
if (family >= AF_MAX) return;
- mutex_lock(&sock_diag_table_mutex); - BUG_ON(sock_diag_handlers[family] != hnld); - WRITE_ONCE(sock_diag_handlers[family], NULL); - mutex_unlock(&sock_diag_table_mutex); + xchg((const struct sock_diag_handler **)&sock_diag_handlers[family], + NULL); } EXPORT_SYMBOL_GPL(sock_diag_unregister);
@@ -227,20 +238,20 @@ static int __sock_diag_cmd(struct sk_buff *skb, struct nlmsghdr *nlh) return -EINVAL; req->sdiag_family = array_index_nospec(req->sdiag_family, AF_MAX);
- if (READ_ONCE(sock_diag_handlers[req->sdiag_family]) == NULL) + if (!rcu_access_pointer(sock_diag_handlers[req->sdiag_family])) sock_load_diag_module(req->sdiag_family, 0);
- mutex_lock(&sock_diag_table_mutex); - hndl = sock_diag_handlers[req->sdiag_family]; + hndl = sock_diag_lock_handler(req->sdiag_family); if (hndl == NULL) - err = -ENOENT; - else if (nlh->nlmsg_type == SOCK_DIAG_BY_FAMILY) + return -ENOENT; + + if (nlh->nlmsg_type == SOCK_DIAG_BY_FAMILY) err = hndl->dump(skb, nlh); else if (nlh->nlmsg_type == SOCK_DESTROY && hndl->destroy) err = hndl->destroy(skb, nlh); else err = -EOPNOTSUPP; - mutex_unlock(&sock_diag_table_mutex); + sock_diag_unlock_handler(hndl);
return err; } @@ -286,12 +297,12 @@ static int sock_diag_bind(struct net *net, int group) switch (group) { case SKNLGRP_INET_TCP_DESTROY: case SKNLGRP_INET_UDP_DESTROY: - if (!READ_ONCE(sock_diag_handlers[AF_INET])) + if (!rcu_access_pointer(sock_diag_handlers[AF_INET])) sock_load_diag_module(AF_INET, 0); break; case SKNLGRP_INET6_TCP_DESTROY: case SKNLGRP_INET6_UDP_DESTROY: - if (!READ_ONCE(sock_diag_handlers[AF_INET6])) + if (!rcu_access_pointer(sock_diag_handlers[AF_INET6])) sock_load_diag_module(AF_INET6, 0); break; }