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netfilter: x_tables: check standard verdicts in core

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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@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
This commit is contained in:
Florian Westphal 2018-02-27 19:42:27 +01:00 committed by Pablo Neira Ayuso
parent f31e5f1a89
commit 07a9da51b4
4 changed files with 43 additions and 21 deletions
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5
net/ipv4/netfilter/arp_tables.c
View File

@ -334,11 +334,6 @@ static int mark_source_chains(const struct xt_table_info *newinfo,
t->verdict < 0) || visited) { t->verdict < 0) || visited) {
unsigned int oldpos, size; 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 /* Return: backtrack through the last
* big jump. * big jump.
*/ */

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

@ -402,11 +402,6 @@ mark_source_chains(const struct xt_table_info *newinfo,
t->verdict < 0) || visited) { t->verdict < 0) || visited) {
unsigned int oldpos, size; 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 /* Return: backtrack through the last
big jump. */ big jump. */
do { do {

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

@ -420,11 +420,6 @@ mark_source_chains(const struct xt_table_info *newinfo,
t->verdict < 0) || visited) { t->verdict < 0) || visited) {
unsigned int oldpos, size; 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 /* Return: backtrack through the last
big jump. */ big jump. */
do { do {

49
net/netfilter/x_tables.c
View File

@ -654,6 +654,31 @@ struct compat_xt_standard_target {
compat_uint_t verdict; 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, int xt_compat_check_entry_offsets(const void *base, const char *elems,
unsigned int target_offset, unsigned int target_offset,
unsigned int next_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) if (target_offset + t->u.target_size > next_offset)
return -EINVAL; return -EINVAL;
if (strcmp(t->u.user.name, XT_STANDARD_TARGET) == 0 && if (strcmp(t->u.user.name, XT_STANDARD_TARGET) == 0) {
COMPAT_XT_ALIGN(target_offset + sizeof(struct compat_xt_standard_target)) != next_offset) const struct compat_xt_standard_target *st = (const void *)t;
return -EINVAL;
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, /* compat_xt_entry match has less strict alignment requirements,
* otherwise they are identical. In case of padding differences * 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) if (target_offset + t->u.target_size > next_offset)
return -EINVAL; return -EINVAL;
if (strcmp(t->u.user.name, XT_STANDARD_TARGET) == 0 && if (strcmp(t->u.user.name, XT_STANDARD_TARGET) == 0) {
XT_ALIGN(target_offset + sizeof(struct xt_standard_target)) != next_offset) const struct xt_standard_target *st = (const void *)t;
return -EINVAL;
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, return xt_check_entry_match(elems, base + target_offset,
__alignof__(struct xt_entry_match)); __alignof__(struct xt_entry_match));