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authorDavid S. Miller <davem@davemloft.net>2005-06-26 15:35:08 -0700
committerChris Wright <chrisw@osdl.org>2005-06-29 16:00:39 -0700
commit1b1f8246322cf10429b1a06924e93423af2bb2ee (patch)
tree6a1ca06954e541e1e84fffabbf30556e44001c4b
parent1ef0867a529b222b8ff659d68140df8d5d6a45f2 (diff)
[PATCH] Fix two socket hashing bugs.
1) netlink_release() should only decrement the hash entry count if the socket was actually hashed. This was causing hash->entries to underflow, which resulting in all kinds of troubles. On 64-bit systems, this would cause the following conditional to erroneously trigger: err = -ENOMEM; if (BITS_PER_LONG > 32 && unlikely(hash->entries >= UINT_MAX)) goto err; 2) netlink_autobind() needs to propagate the error return from netlink_insert(). Otherwise, callers will not see the error as they should and thus try to operate on a socket with a zero pid, which is very bad. However, it should not propagate -EBUSY. If two threads race to autobind the socket, that is fine. This is consistent with the autobind behavior in other protocols. So bug #1 above, combined with this one, resulted in hangs on netlink_sendmsg() calls to the rtnetlink socket. We'd try to do the user sendmsg() with the socket's pid set to zero, later we do a socket lookup using that pid (via the value we stashed away in NETLINK_CB(skb).pid), but that won't give us the user socket, it will give us the rtnetlink socket. So when we try to wake up the receive queue, we dive back into rtnetlink_rcv() which tries to recursively take the rtnetlink semaphore. Thanks to Jakub Jelink for providing backtraces. Also, thanks to Herbert Xu for supplying debugging patches to help track this down, and also finding a mistake in an earlier version of this fix. Signed-off-by: David S. Miller <davem@davemloft.net> Signed-off-by: Chris Wright <chrisw@osdl.org>
-rw-r--r--net/netlink/af_netlink.c11
1 files changed, 8 insertions, 3 deletions
diff --git a/net/netlink/af_netlink.c b/net/netlink/af_netlink.c
index e41ce458c2a9..d9b118c986e8 100644
--- a/net/netlink/af_netlink.c
+++ b/net/netlink/af_netlink.c
@@ -315,8 +315,8 @@ err:
static void netlink_remove(struct sock *sk)
{
netlink_table_grab();
- nl_table[sk->sk_protocol].hash.entries--;
- sk_del_node_init(sk);
+ if (sk_del_node_init(sk))
+ nl_table[sk->sk_protocol].hash.entries--;
if (nlk_sk(sk)->groups)
__sk_del_bind_node(sk);
netlink_table_ungrab();
@@ -429,7 +429,12 @@ retry:
err = netlink_insert(sk, pid);
if (err == -EADDRINUSE)
goto retry;
- return 0;
+
+ /* If 2 threads race to autobind, that is fine. */
+ if (err == -EBUSY)
+ err = 0;
+
+ return err;
}
static inline int netlink_capable(struct socket *sock, unsigned int flag)