netfilter: xtables: ignore unassigned hooks in check_entry_size_and_hooks
The "hook_entry" and "underflow" array contains values even for hooks
not provided, such as PREROUTING in conjunction with the "filter"
table. Usually, the values point to whatever the next rule is. For
the upcoming unconditionality and underflow checking patches however,
we must not inspect that arbitrary rule.
Skipping unassigned hooks seems like a good idea, also because
newinfo->hook_entry and newinfo->underflow will then continue to have
the poison value for detecting abnormalities.
Signed-off-by: Jan Engelhardt <jengelh@medozas.de>
diff --git a/net/ipv4/netfilter/ip_tables.c b/net/ipv4/netfilter/ip_tables.c
index 3431a77..6e7b7e8 100644
--- a/net/ipv4/netfilter/ip_tables.c
+++ b/net/ipv4/netfilter/ip_tables.c
@@ -714,6 +714,7 @@
unsigned char *limit,
const unsigned int *hook_entries,
const unsigned int *underflows,
+ unsigned int valid_hooks,
unsigned int *i)
{
unsigned int h;
@@ -733,6 +734,8 @@
/* Check hooks & underflows */
for (h = 0; h < NF_INET_NUMHOOKS; h++) {
+ if (!(valid_hooks & (1 << h)))
+ continue;
if ((unsigned char *)e - base == hook_entries[h])
newinfo->hook_entry[h] = hook_entries[h];
if ((unsigned char *)e - base == underflows[h])
@@ -804,7 +807,7 @@
newinfo,
entry0,
entry0 + size,
- hook_entries, underflows, &i);
+ hook_entries, underflows, valid_hooks, &i);
if (ret != 0)
return ret;