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Commit 07a9da51 authored by Florian Westphal's avatar Florian Westphal Committed by Pablo Neira Ayuso
Browse files

netfilter: x_tables: check standard verdicts in core 



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: default avatarFlorian Westphal <fw@strlen.de>
Signed-off-by: default avatarPablo Neira Ayuso <pablo@netfilter.org>
parent f31e5f1a

net/ipv4/netfilter/arp_tables.c

+0 −5
Original line number Diff line number Diff line
@@ -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.

				 */

net/ipv4/netfilter/ip_tables.c

+0 −5
Original line number Diff line number Diff line
@@ -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 {

net/ipv6/netfilter/ip6_tables.c

+0 −5
Original line number Diff line number Diff line
@@ -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 {

net/netfilter/x_tables.c

+43 −6
Original line number Diff line number Diff line
@@ -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)

	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)

	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));