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[NETFILTER]: {ip,ip6,arp}_tables: fix exponential worst-case search for loops

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If we come to node we'd already marked as seen and it's not a part of path
(i.e. we don't have a loop right there), we already know that it isn't a
part of any loop, so we don't need to revisit it.

That speeds the things up if some chain is refered to from several places
and kills O(exp(table size)) worst-case behaviour (without sleeping,
at that, so if you manage to self-LART that way, you are SOL for a long
time)...

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Al Viro 2006-12-12 00:29:52 -08:00 • committed by David S. Miller
commit e1b4b9f398
3 changed files with 9 additions and 6 deletions
Download patch file Download diff file Expand all files Collapse all files

5
net/ipv4/netfilter/arp_tables.c
View file

@ -358,6 +358,7 @@ static int mark_source_chains(struct xt_table_info *newinfo,
for (;;) { for (;;) {
struct arpt_standard_target *t struct arpt_standard_target *t
= (void *)arpt_get_target(e); = (void *)arpt_get_target(e);
int visited = e->comefrom & (1 << hook);
if (e->comefrom & (1 << NF_ARP_NUMHOOKS)) { if (e->comefrom & (1 << NF_ARP_NUMHOOKS)) {
printk("arptables: loop hook %u pos %u %08X.\n", printk("arptables: loop hook %u pos %u %08X.\n",
@ -368,11 +369,11 @@ static int mark_source_chains(struct xt_table_info *newinfo,
|= ((1 << hook) | (1 << NF_ARP_NUMHOOKS)); |= ((1 << hook) | (1 << NF_ARP_NUMHOOKS));
/* Unconditional return/END. */ /* Unconditional return/END. */
if (e->target_offset == sizeof(struct arpt_entry) if ((e->target_offset == sizeof(struct arpt_entry)
&& (strcmp(t->target.u.user.name, && (strcmp(t->target.u.user.name,
ARPT_STANDARD_TARGET) == 0) ARPT_STANDARD_TARGET) == 0)
&& t->verdict < 0 && t->verdict < 0
&& unconditional(&e->arp)) { && unconditional(&e->arp)) || visited) {
unsigned int oldpos, size; unsigned int oldpos, size;
if (t->verdict < -NF_MAX_VERDICT - 1) { if (t->verdict < -NF_MAX_VERDICT - 1) {

5
net/ipv4/netfilter/ip_tables.c
View file

@ -384,6 +384,7 @@ mark_source_chains(struct xt_table_info *newinfo,
for (;;) { for (;;) {
struct ipt_standard_target *t struct ipt_standard_target *t
= (void *)ipt_get_target(e); = (void *)ipt_get_target(e);
int visited = e->comefrom & (1 << hook);
if (e->comefrom & (1 << NF_IP_NUMHOOKS)) { if (e->comefrom & (1 << NF_IP_NUMHOOKS)) {
printk("iptables: loop hook %u pos %u %08X.\n", printk("iptables: loop hook %u pos %u %08X.\n",
@ -394,11 +395,11 @@ mark_source_chains(struct xt_table_info *newinfo,
|= ((1 << hook) | (1 << NF_IP_NUMHOOKS)); |= ((1 << hook) | (1 << NF_IP_NUMHOOKS));
/* Unconditional return/END. */ /* Unconditional return/END. */
if (e->target_offset == sizeof(struct ipt_entry) if ((e->target_offset == sizeof(struct ipt_entry)
&& (strcmp(t->target.u.user.name, && (strcmp(t->target.u.user.name,
IPT_STANDARD_TARGET) == 0) IPT_STANDARD_TARGET) == 0)
&& t->verdict < 0 && t->verdict < 0
&& unconditional(&e->ip)) { && unconditional(&e->ip)) || visited) {
unsigned int oldpos, size; unsigned int oldpos, size;
if (t->verdict < -NF_MAX_VERDICT - 1) { if (t->verdict < -NF_MAX_VERDICT - 1) {

5
net/ipv6/netfilter/ip6_tables.c
View file

@ -413,6 +413,7 @@ mark_source_chains(struct xt_table_info *newinfo,
unsigned int pos = newinfo->hook_entry[hook]; unsigned int pos = newinfo->hook_entry[hook];
struct ip6t_entry *e struct ip6t_entry *e
= (struct ip6t_entry *)(entry0 + pos); = (struct ip6t_entry *)(entry0 + pos);
int visited = e->comefrom & (1 << hook);
if (!(valid_hooks & (1 << hook))) if (!(valid_hooks & (1 << hook)))
continue; continue;
@ -433,11 +434,11 @@ mark_source_chains(struct xt_table_info *newinfo,
|= ((1 << hook) | (1 << NF_IP6_NUMHOOKS)); |= ((1 << hook) | (1 << NF_IP6_NUMHOOKS));
/* Unconditional return/END. */ /* Unconditional return/END. */
if (e->target_offset == sizeof(struct ip6t_entry) if ((e->target_offset == sizeof(struct ip6t_entry)
&& (strcmp(t->target.u.user.name, && (strcmp(t->target.u.user.name,
IP6T_STANDARD_TARGET) == 0) IP6T_STANDARD_TARGET) == 0)
&& t->verdict < 0 && t->verdict < 0
&& unconditional(&e->ipv6)) { && unconditional(&e->ipv6)) || visited) {
unsigned int oldpos, size; unsigned int oldpos, size;
if (t->verdict < -NF_MAX_VERDICT - 1) { if (t->verdict < -NF_MAX_VERDICT - 1) {