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[TCP/DCCP]: Randomize port selection

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This patch randomizes the port selected on bind() for connections
to help with possible security attacks. It should also be faster
in most cases because there is no need for a global lock.

Signed-off-by: Stephen Hemminger <shemminger@osdl.org>
Signed-off-by: Arnaldo Carvalho de Melo <acme@mandriva.com>
This commit is contained in:
Stephen Hemminger 2005-11-03 16:33:23 -08:00 committed by Arnaldo Carvalho de Melo
parent 6151b31c96
commit 6df716340d
6 changed files with 10 additions and 56 deletions
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2
include/net/inet_hashtables.h
View file

@ -125,9 +125,7 @@ struct inet_hashinfo {
rwlock_t lhash_lock ____cacheline_aligned;
atomic_t lhash_users;
wait_queue_head_t lhash_wait;
spinlock_t portalloc_lock;
kmem_cache_t *bind_bucket_cachep;
int port_rover;
};
static inline unsigned int inet_ehashfn(const __u32 laddr, const __u16 lport,

32
net/dccp/ipv4.c
View file

@ -31,8 +31,6 @@ struct inet_hashinfo __cacheline_aligned dccp_hashinfo = {
.lhash_lock = RW_LOCK_UNLOCKED,
.lhash_users = ATOMIC_INIT(0),
.lhash_wait = __WAIT_QUEUE_HEAD_INITIALIZER(dccp_hashinfo.lhash_wait),
.portalloc_lock = SPIN_LOCK_UNLOCKED,
.port_rover = 1024 - 1,
};
EXPORT_SYMBOL_GPL(dccp_hashinfo);
@ -125,36 +123,15 @@ static int dccp_v4_hash_connect(struct sock *sk)
int ret;
if (snum == 0) {
int rover;
int low = sysctl_local_port_range[0];
int high = sysctl_local_port_range[1];
int remaining = (high - low) + 1;
int rover = net_random() % (high - low) + low;
struct hlist_node *node;
struct inet_timewait_sock *tw = NULL;
local_bh_disable();
/* TODO. Actually it is not so bad idea to remove
* dccp_hashinfo.portalloc_lock before next submission to
* Linus.
* As soon as we touch this place at all it is time to think.
*
* Now it protects single _advisory_ variable
* dccp_hashinfo.port_rover, hence it is mostly useless.
* Code will work nicely if we just delete it, but
* I am afraid in contented case it will work not better or
* even worse: another cpu just will hit the same bucket
* and spin there.
* So some cpu salt could remove both contention and
* memory pingpong. Any ideas how to do this in a nice way?
*/
spin_lock(&dccp_hashinfo.portalloc_lock);
rover = dccp_hashinfo.port_rover;
do {
rover++;
if ((rover < low) || (rover > high))
rover = low;
head = &dccp_hashinfo.bhash[inet_bhashfn(rover,
dccp_hashinfo.bhash_size)];
spin_lock(&head->lock);
@ -187,9 +164,9 @@ static int dccp_v4_hash_connect(struct sock *sk)
next_port:
spin_unlock(&head->lock);
if (++rover > high)
rover = low;
} while (--remaining > 0);
dccp_hashinfo.port_rover = rover;
spin_unlock(&dccp_hashinfo.portalloc_lock);
local_bh_enable();
@ -197,9 +174,6 @@ static int dccp_v4_hash_connect(struct sock *sk)
ok:
/* All locks still held and bhs disabled */
dccp_hashinfo.port_rover = rover;
spin_unlock(&dccp_hashinfo.portalloc_lock);
inet_bind_hash(sk, tb, rover);
if (sk_unhashed(sk)) {
inet_sk(sk)->sport = htons(rover);

14
net/ipv4/inet_connection_sock.c
View file

@ -78,17 +78,9 @@ int inet_csk_get_port(struct inet_hashinfo *hashinfo,
int low = sysctl_local_port_range[0];
int high = sysctl_local_port_range[1];
int remaining = (high - low) + 1;
int rover;
int rover = net_random() % (high - low) + low;
spin_lock(&hashinfo->portalloc_lock);
if (hashinfo->port_rover < low)
rover = low;
else
rover = hashinfo->port_rover;
do {
rover++;
if (rover > high)
rover = low;
head = &hashinfo->bhash[inet_bhashfn(rover, hashinfo->bhash_size)];
spin_lock(&head->lock);
inet_bind_bucket_for_each(tb, node, &head->chain)
@ -97,9 +89,9 @@ int inet_csk_get_port(struct inet_hashinfo *hashinfo,
break;
next:
spin_unlock(&head->lock);
if (++rover > high)
rover = low;
} while (--remaining > 0);
hashinfo->port_rover = rover;
spin_unlock(&hashinfo->portalloc_lock);
/* Exhausted local port range during search? It is not
* possible for us to be holding one of the bind hash

1
net/ipv4/tcp.c
View file

@ -2112,7 +2112,6 @@ void __init tcp_init(void)
sysctl_tcp_max_orphans >>= (3 - order);
sysctl_max_syn_backlog = 128;
}
tcp_hashinfo.port_rover = sysctl_local_port_range[0] - 1;
sysctl_tcp_mem[0] = 768 << order;
sysctl_tcp_mem[1] = 1024 << order;

2
net/ipv4/tcp_ipv4.c
View file

@ -93,8 +93,6 @@ struct inet_hashinfo __cacheline_aligned tcp_hashinfo = {
.lhash_lock = RW_LOCK_UNLOCKED,
.lhash_users = ATOMIC_INIT(0),
.lhash_wait = __WAIT_QUEUE_HEAD_INITIALIZER(tcp_hashinfo.lhash_wait),
.portalloc_lock = SPIN_LOCK_UNLOCKED,
.port_rover = 1024 - 1,
};
static int tcp_v4_get_port(struct sock *sk, unsigned short snum)

15
net/ipv6/tcp_ipv6.c
View file

@ -114,16 +114,9 @@ static int tcp_v6_get_port(struct sock *sk, unsigned short snum)
int low = sysctl_local_port_range[0];
int high = sysctl_local_port_range[1];
int remaining = (high - low) + 1;
int rover;
int rover = net_random() % (high - low) + low;
spin_lock(&tcp_hashinfo.portalloc_lock);
if (tcp_hashinfo.port_rover < low)
rover = low;
else
rover = tcp_hashinfo.port_rover;
do { rover++;
if (rover > high)
rover = low;
do {
head = &tcp_hashinfo.bhash[inet_bhashfn(rover, tcp_hashinfo.bhash_size)];
spin_lock(&head->lock);
inet_bind_bucket_for_each(tb, node, &head->chain)
@ -132,9 +125,9 @@ static int tcp_v6_get_port(struct sock *sk, unsigned short snum)
break;
next:
spin_unlock(&head->lock);
if (++rover > high)
rover = low;
} while (--remaining > 0);
tcp_hashinfo.port_rover = rover;
spin_unlock(&tcp_hashinfo.portalloc_lock);
/* Exhausted local port range during search? It is not
* possible for us to be holding one of the bind hash