udp: udp_lib_get_port() fix

Now we can have a large udp hash table, udp_lib_get_port() loop
should be converted to a do {} while (cond) form,
or we dont enter it at all if hash table size is exactly 65536.

Reported-by: Yinghai Lu <yinghai@kernel.org>
Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 3 insertions, 4 deletions

diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c
index 1f9534846ca9..f0126fdd7e04 100644
--- a/net/ipv4/udp.c
+++ b/net/ipv4/udp.c
@@ -216,9 +216,8 @@ int udp_lib_get_port(struct sock *sk, unsigned short snum,
                  * force rand to be an odd multiple of UDP_HTABLE_SIZE
                  */
                 rand = (rand | 1) * (udptable->mask + 1);
-                for (last = first + udptable->mask + 1;
-                     first != last;
-                     first++) {
+                last = first + udptable->mask + 1;
+                do {
                         hslot = udp_hashslot(udptable, net, first);
                         bitmap_zero(bitmap, PORTS_PER_CHAIN);
                         spin_lock_bh(&hslot->lock);
@@ -238,7 +237,7 @@ int udp_lib_get_port(struct sock *sk, unsigned short snum,
                                 snum += rand;
                         } while (snum != first);
                         spin_unlock_bh(&hslot->lock);
-                }
+                } while (++first != last);
                 goto fail;
         } else {
                 hslot = udp_hashslot(udptable, net, snum);