aboutsummaryrefslogtreecommitdiffstats
path: root/net/netlink
diff options
context:
space:
mode:
authorHerbert Xu <herbert@gondor.apana.org.au>2015-05-17 02:45:34 (GMT)
committerDavid S. Miller <davem@davemloft.net>2015-05-18 03:43:31 (GMT)
commitb9fbe709de4dbe663613ebb852f35aef2467872c (patch)
tree028eeb771c3f596b66853dce3a22d93425848187 /net/netlink
parentde133464c9e70808d3e5a861294bc55940988178 (diff)
netlink: Use random autobind rover
Currently we use a global rover to select a port ID that is unique. This used to work consistently when it was protected with a global lock. However as we're now lockless, the global rover can exhibit pathological behaviour should multiple threads all stomp on it at the same time. Granted this will eventually resolve itself but the process is suboptimal. This patch replaces the global rover with a pseudorandom starting point to avoid this issue. Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/netlink')
-rw-r--r--net/netlink/af_netlink.c16
1 files changed, 10 insertions, 6 deletions
diff --git a/net/netlink/af_netlink.c b/net/netlink/af_netlink.c
index 164ded7..136056f0 100644
--- a/net/netlink/af_netlink.c
+++ b/net/netlink/af_netlink.c
@@ -1299,20 +1299,24 @@ static int netlink_autobind(struct socket *sock)
struct netlink_table *table = &nl_table[sk->sk_protocol];
s32 portid = task_tgid_vnr(current);
int err;
- static s32 rover = -4097;
+ s32 rover = -4096;
+ bool ok;
retry:
cond_resched();
rcu_read_lock();
- if (__netlink_lookup(table, portid, net)) {
+ ok = !__netlink_lookup(table, portid, net);
+ rcu_read_unlock();
+ if (!ok) {
/* Bind collision, search negative portid values. */
- portid = rover--;
- if (rover > -4097)
+ if (rover == -4096)
+ /* rover will be in range [S32_MIN, -4097] */
+ rover = S32_MIN + prandom_u32_max(-4096 - S32_MIN);
+ else if (rover >= -4096)
rover = -4097;
- rcu_read_unlock();
+ portid = rover--;
goto retry;
}
- rcu_read_unlock();
err = netlink_insert(sk, portid);
if (err == -EADDRINUSE)

Privacy Policy