From: Florian Westphal <fw@xxxxxxxxx>
Userspace must provide a valid verdict to the standard target.
The verdict can be either a jump (signed int > 0), or a return code.
Allowed return codes are either RETURN (pop from stack), NF_ACCEPT, DROP
and QUEUE (latter is allowed for legacy reasons).
Jump offsets (verdict > 0) are checked in more detail later on when
loop-detection is performed.
Signed-off-by: Florian Westphal <fw@xxxxxxxxx>
Signed-off-by: Pablo Neira Ayuso <pablo@xxxxxxxxxxxxx>
---
net/ipv4/netfilter/arp_tables.c | 5 -----
net/ipv4/netfilter/ip_tables.c | 5 -----
net/ipv6/netfilter/ip6_tables.c | 5 -----
net/netfilter/x_tables.c | 49 ++++++++++++++++++++++++++++++++++++-----
4 files changed, 43 insertions(+), 21 deletions(-)
diff --git a/net/ipv4/netfilter/arp_tables.c b/net/ipv4/netfilter/arp_tables.c
index a0c7ce76879c..c9ffa884a4ee 100644
--- a/net/ipv4/netfilter/arp_tables.c
+++ b/net/ipv4/netfilter/arp_tables.c
@@ -334,11 +334,6 @@ static int mark_source_chains(const struct xt_table_info *newinfo,
t->verdict < 0) || visited) {
unsigned int oldpos, size;
- if ((strcmp(t->target.u.user.name,
- XT_STANDARD_TARGET) == 0) &&
- t->verdict < -NF_MAX_VERDICT - 1)
- return 0;
-
/* Return: backtrack through the last
* big jump.
*/
diff --git a/net/ipv4/netfilter/ip_tables.c b/net/ipv4/netfilter/ip_tables.c
index 4f7153e25e0b..c9b57a6bf96a 100644
--- a/net/ipv4/netfilter/ip_tables.c
+++ b/net/ipv4/netfilter/ip_tables.c
@@ -402,11 +402,6 @@ mark_source_chains(const struct xt_table_info *newinfo,
t->verdict < 0) || visited) {
unsigned int oldpos, size;
- if ((strcmp(t->target.u.user.name,
- XT_STANDARD_TARGET) == 0) &&
- t->verdict < -NF_MAX_VERDICT - 1)
- return 0;
-
/* Return: backtrack through the last
big jump. */
do {
diff --git a/net/ipv6/netfilter/ip6_tables.c b/net/ipv6/netfilter/ip6_tables.c
index 6c44033decab..f46954221933 100644
--- a/net/ipv6/netfilter/ip6_tables.c
+++ b/net/ipv6/netfilter/ip6_tables.c
@@ -420,11 +420,6 @@ mark_source_chains(const struct xt_table_info *newinfo,
t->verdict < 0) || visited) {
unsigned int oldpos, size;
- if ((strcmp(t->target.u.user.name,
- XT_STANDARD_TARGET) == 0) &&
- t->verdict < -NF_MAX_VERDICT - 1)
- return 0;
-
/* Return: backtrack through the last
big jump. */
do {
diff --git a/net/netfilter/x_tables.c b/net/netfilter/x_tables.c
index d9deebe599ec..2e4d423e58e6 100644
--- a/net/netfilter/x_tables.c
+++ b/net/netfilter/x_tables.c
@@ -654,6 +654,31 @@ struct compat_xt_standard_target {
compat_uint_t verdict;
};
+static bool verdict_ok(int verdict)
+{
+ if (verdict > 0)
+ return true;
+
+ if (verdict < 0) {
+ int v = -verdict - 1;
+
+ if (verdict == XT_RETURN)
+ return true;
+
+ switch (v) {
+ case NF_ACCEPT: return true;
+ case NF_DROP: return true;
+ case NF_QUEUE: return true;
+ default:
+ break;
+ }
+
+ return false;
+ }
+
+ return false;
+}
+
int xt_compat_check_entry_offsets(const void *base, const char *elems,
unsigned int target_offset,
unsigned int next_offset)
@@ -675,9 +700,15 @@ int xt_compat_check_entry_offsets(const void *base, const char *elems,
if (target_offset + t->u.target_size > next_offset)
return -EINVAL;
- if (strcmp(t->u.user.name, XT_STANDARD_TARGET) == 0 &&
- COMPAT_XT_ALIGN(target_offset + sizeof(struct compat_xt_standard_target)) != next_offset)
- return -EINVAL;
+ if (strcmp(t->u.user.name, XT_STANDARD_TARGET) == 0) {
+ const struct compat_xt_standard_target *st = (const void *)t;
+
+ if (COMPAT_XT_ALIGN(target_offset + sizeof(*st)) != next_offset)
+ return -EINVAL;
+
+ if (!verdict_ok(st->verdict))
+ return -EINVAL;
+ }
/* compat_xt_entry match has less strict alignment requirements,
* otherwise they are identical. In case of padding differences
@@ -757,9 +788,15 @@ int xt_check_entry_offsets(const void *base,
if (target_offset + t->u.target_size > next_offset)
return -EINVAL;
- if (strcmp(t->u.user.name, XT_STANDARD_TARGET) == 0 &&
- XT_ALIGN(target_offset + sizeof(struct xt_standard_target)) != next_offset)
- return -EINVAL;
+ if (strcmp(t->u.user.name, XT_STANDARD_TARGET) == 0) {
+ const struct xt_standard_target *st = (const void *)t;
+
+ if (XT_ALIGN(target_offset + sizeof(*st)) != next_offset)
+ return -EINVAL;
+
+ if (!verdict_ok(st->verdict))
+ return -EINVAL;
+ }
return xt_check_entry_match(elems, base + target_offset,
__alignof__(struct xt_entry_match));
--
2.11.0
--
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