From 076931989fe96823a577259cc6bc205d7ec31754 Mon Sep 17 00:00:00 2001 From: Pavel Emelyanov Date: Fri, 30 Nov 2007 00:08:14 +1100 Subject: [PATCH] [INET]: Fix inet_diag register vs rcv race The following race is possible when one cpu unregisters the handler while other one is trying to receive a message and call this one: CPU1: CPU2: inet_diag_rcv() inet_diag_unregister() mutex_lock(&inet_diag_mutex); netlink_rcv_skb(skb, &inet_diag_rcv_msg); if (inet_diag_table[nlh->nlmsg_type] == NULL) /* false handler is still registered */ ... netlink_dump_start(idiagnl, skb, nlh, inet_diag_dump, NULL); cb = kzalloc(sizeof(*cb), GFP_KERNEL); /* sleep here freeing memory * or preempt * or sleep later on nlk->cb_mutex */ spin_lock(&inet_diag_register_lock); inet_diag_table[type] = NULL; ... spin_unlock(&inet_diag_register_lock); synchronize_rcu(); /* CPU1 is sleeping - RCU quiescent * state is passed */ return; /* inet_diag_dump is finally called: */ inet_diag_dump() handler = inet_diag_table[cb->nlh->nlmsg_type]; BUG_ON(handler == NULL); /* OOPS! While we slept the unregister has set * handler to NULL :( */ Grep showed, that the register/unregister functions are called from init/fini module callbacks for tcp_/dccp_diag, so it's OK to use the inet_diag_mutex to synchronize manipulations with the inet_diag_table and the access to it. Besides, as Herbert pointed out, asynchronous dumps should hold this mutex as well, and thus, we provide the mutex as cb_mutex one. Signed-off-by: Pavel Emelyanov Signed-off-by: Herbert Xu --- net/ipv4/inet_diag.c | 14 +++++--------- 1 file changed, 5 insertions(+), 9 deletions(-) diff --git a/net/ipv4/inet_diag.c b/net/ipv4/inet_diag.c index b0170732b5e9..6b3fffb554b6 100644 --- a/net/ipv4/inet_diag.c +++ b/net/ipv4/inet_diag.c @@ -853,8 +853,6 @@ static void inet_diag_rcv(struct sk_buff *skb) mutex_unlock(&inet_diag_mutex); } -static DEFINE_SPINLOCK(inet_diag_register_lock); - int inet_diag_register(const struct inet_diag_handler *h) { const __u16 type = h->idiag_type; @@ -863,13 +861,13 @@ int inet_diag_register(const struct inet_diag_handler *h) if (type >= INET_DIAG_GETSOCK_MAX) goto out; - spin_lock(&inet_diag_register_lock); + mutex_lock(&inet_diag_mutex); err = -EEXIST; if (inet_diag_table[type] == NULL) { inet_diag_table[type] = h; err = 0; } - spin_unlock(&inet_diag_register_lock); + mutex_unlock(&inet_diag_mutex); out: return err; } @@ -882,11 +880,9 @@ void inet_diag_unregister(const struct inet_diag_handler *h) if (type >= INET_DIAG_GETSOCK_MAX) return; - spin_lock(&inet_diag_register_lock); + mutex_lock(&inet_diag_mutex); inet_diag_table[type] = NULL; - spin_unlock(&inet_diag_register_lock); - - synchronize_rcu(); + mutex_unlock(&inet_diag_mutex); } EXPORT_SYMBOL_GPL(inet_diag_unregister); @@ -901,7 +897,7 @@ static int __init inet_diag_init(void) goto out; idiagnl = netlink_kernel_create(&init_net, NETLINK_INET_DIAG, 0, - inet_diag_rcv, NULL, THIS_MODULE); + inet_diag_rcv, &inet_diag_mutex, THIS_MODULE); if (idiagnl == NULL) goto out_free_table; err = 0; -- 2.20.1