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Commit ce683e5f authored by Florian Westphal's avatar Florian Westphal Committed by Pablo Neira Ayuso
Browse files

netfilter: x_tables: check for bogus target offset 



We're currently asserting that targetoff + targetsize <= nextoff.

Extend it to also check that targetoff is >= sizeof(xt_entry).
Since this is generic code, add an argument pointing to the start of the
match/target, we can then derive the base structure size from the delta.

We also need the e->elems pointer in a followup change to validate matches.

Signed-off-by: default avatarFlorian Westphal <fw@strlen.de>
Signed-off-by: default avatarPablo Neira Ayuso <pablo@netfilter.org>
parent 7ed2abdd

include/linux/netfilter/x_tables.h

+2 −2
Original line number Diff line number Diff line
@@ -242,7 +242,7 @@ void xt_unregister_match(struct xt_match *target); 
int xt_register_matches(struct xt_match *match, unsigned int n);

void xt_unregister_matches(struct xt_match *match, unsigned int n);



int xt_check_entry_offsets(const void *base,

int xt_check_entry_offsets(const void *base, const char *elems,

			   unsigned int target_offset,

			   unsigned int next_offset);
@@ -494,7 +494,7 @@ void xt_compat_target_from_user(struct xt_entry_target *t, void **dstptr, 
				unsigned int *size);

int xt_compat_target_to_user(const struct xt_entry_target *t,

			     void __user **dstptr, unsigned int *size);

int xt_compat_check_entry_offsets(const void *base,

int xt_compat_check_entry_offsets(const void *base, const char *elems,

				  unsigned int target_offset,

				  unsigned int next_offset);

net/ipv4/netfilter/arp_tables.c

+3 −2
Original line number Diff line number Diff line
@@ -592,7 +592,8 @@ static inline int check_entry_size_and_hooks(struct arpt_entry *e, 
	if (!arp_checkentry(&e->arp))

		return -EINVAL;



	err = xt_check_entry_offsets(e, e->target_offset, e->next_offset);

	err = xt_check_entry_offsets(e, e->elems, e->target_offset,

				     e->next_offset);

	if (err)

		return err;
@@ -1254,7 +1255,7 @@ check_compat_entry_size_and_hooks(struct compat_arpt_entry *e, 
	if (!arp_checkentry(&e->arp))

		return -EINVAL;



	ret = xt_compat_check_entry_offsets(e, e->target_offset,

	ret = xt_compat_check_entry_offsets(e, e->elems, e->target_offset,

					    e->next_offset);

	if (ret)

		return ret;

net/ipv4/netfilter/ip_tables.c

+3 −2
Original line number Diff line number Diff line
@@ -754,7 +754,8 @@ check_entry_size_and_hooks(struct ipt_entry *e, 
	if (!ip_checkentry(&e->ip))

		return -EINVAL;



	err = xt_check_entry_offsets(e, e->target_offset, e->next_offset);

	err = xt_check_entry_offsets(e, e->elems, e->target_offset,

				     e->next_offset);

	if (err)

		return err;
@@ -1513,7 +1514,7 @@ check_compat_entry_size_and_hooks(struct compat_ipt_entry *e, 
	if (!ip_checkentry(&e->ip))

		return -EINVAL;



	ret = xt_compat_check_entry_offsets(e,

	ret = xt_compat_check_entry_offsets(e, e->elems,

					    e->target_offset, e->next_offset);

	if (ret)

		return ret;

net/ipv6/netfilter/ip6_tables.c

+3 −2
Original line number Diff line number Diff line
@@ -766,7 +766,8 @@ check_entry_size_and_hooks(struct ip6t_entry *e, 
	if (!ip6_checkentry(&e->ipv6))

		return -EINVAL;



	err = xt_check_entry_offsets(e, e->target_offset, e->next_offset);

	err = xt_check_entry_offsets(e, e->elems, e->target_offset,

				     e->next_offset);

	if (err)

		return err;
@@ -1525,7 +1526,7 @@ check_compat_entry_size_and_hooks(struct compat_ip6t_entry *e, 
	if (!ip6_checkentry(&e->ipv6))

		return -EINVAL;



	ret = xt_compat_check_entry_offsets(e,

	ret = xt_compat_check_entry_offsets(e, e->elems,

					    e->target_offset, e->next_offset);

	if (ret)

		return ret;

net/netfilter/x_tables.c

+15 −2
Original line number Diff line number Diff line
@@ -546,14 +546,17 @@ struct compat_xt_standard_target { 
	compat_uint_t verdict;

};



/* see xt_check_entry_offsets */

int xt_compat_check_entry_offsets(const void *base,

int xt_compat_check_entry_offsets(const void *base, const char *elems,

				  unsigned int target_offset,

				  unsigned int next_offset)

{

	long size_of_base_struct = elems - (const char *)base;

	const struct compat_xt_entry_target *t;

	const char *e = base;



	if (target_offset < size_of_base_struct)

		return -EINVAL;



	if (target_offset + sizeof(*t) > next_offset)

		return -EINVAL;
@@ -577,12 +580,16 @@ EXPORT_SYMBOL(xt_compat_check_entry_offsets); 
 * xt_check_entry_offsets - validate arp/ip/ip6t_entry

 *

 * @base: pointer to arp/ip/ip6t_entry

 * @elems: pointer to first xt_entry_match, i.e. ip(6)t_entry->elems

 * @target_offset: the arp/ip/ip6_t->target_offset

 * @next_offset: the arp/ip/ip6_t->next_offset

 *

 * validates that target_offset and next_offset are sane.

 * Also see xt_compat_check_entry_offsets for CONFIG_COMPAT version.

 *

 * This function does not validate the targets or matches themselves, it

 * only tests that all the offsets and sizes are correct.

 *

 * The arp/ip/ip6t_entry structure @base must have passed following tests:

 * - it must point to a valid memory location

 * - base to base + next_offset must be accessible, i.e. not exceed allocated
@@ -591,12 +598,18 @@ EXPORT_SYMBOL(xt_compat_check_entry_offsets); 
 * Return: 0 on success, negative errno on failure.

 */

int xt_check_entry_offsets(const void *base,

			   const char *elems,

			   unsigned int target_offset,

			   unsigned int next_offset)

{

	long size_of_base_struct = elems - (const char *)base;

	const struct xt_entry_target *t;

	const char *e = base;



	/* target start is within the ip/ip6/arpt_entry struct */

	if (target_offset < size_of_base_struct)

		return -EINVAL;



	if (target_offset + sizeof(*t) > next_offset)

		return -EINVAL;