Commit 7d35812c authored by Florian Westphal's avatar Florian Westphal Committed by Pablo Neira Ayuso
Browse files

netfilter: x_tables: add and use xt_check_entry_offsets 



Currently arp/ip and ip6tables each implement a short helper to check that
the target offset is large enough to hold one xt_entry_target struct and
that t->u.target_size fits within the current rule.

Unfortunately these checks are not sufficient.

To avoid adding new tests to all of ip/ip6/arptables move the current
checks into a helper, then extend this helper in followup patches.

Signed-off-by: default avatarFlorian Westphal <fw@strlen.de>
Signed-off-by: default avatarPablo Neira Ayuso <pablo@netfilter.org>
parent 36472341

include/linux/netfilter/x_tables.h

+4 −0
Original line number Diff line number Diff line
@@ -242,6 +242,10 @@ 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,

			   unsigned int target_offset,

			   unsigned int next_offset);



int xt_check_match(struct xt_mtchk_param *, unsigned int size, u_int8_t proto,

		   bool inv_proto);

int xt_check_target(struct xt_tgchk_param *, unsigned int size, u_int8_t proto,

net/ipv4/netfilter/arp_tables.c

+1 −10
Original line number Diff line number Diff line
@@ -496,19 +496,10 @@ next: 


static inline int check_entry(const struct arpt_entry *e)

{

	const struct xt_entry_target *t;



	if (!arp_checkentry(&e->arp))

		return -EINVAL;



	if (e->target_offset + sizeof(struct xt_entry_target) > e->next_offset)

		return -EINVAL;



	t = arpt_get_target_c(e);

	if (e->target_offset + t->u.target_size > e->next_offset)

		return -EINVAL;



	return 0;

	return xt_check_entry_offsets(e, e->target_offset, e->next_offset);

}



static inline int check_target(struct arpt_entry *e, const char *name)

net/ipv4/netfilter/ip_tables.c

+1 −11
Original line number Diff line number Diff line
@@ -590,20 +590,10 @@ static void cleanup_match(struct xt_entry_match *m, struct net *net) 
static int

check_entry(const struct ipt_entry *e)

{

	const struct xt_entry_target *t;



	if (!ip_checkentry(&e->ip))

		return -EINVAL;



	if (e->target_offset + sizeof(struct xt_entry_target) >

	    e->next_offset)

		return -EINVAL;



	t = ipt_get_target_c(e);

	if (e->target_offset + t->u.target_size > e->next_offset)

		return -EINVAL;



	return 0;

	return xt_check_entry_offsets(e, e->target_offset, e->next_offset);

}



static int

net/ipv6/netfilter/ip6_tables.c

+1 −11
Original line number Diff line number Diff line
@@ -602,20 +602,10 @@ static void cleanup_match(struct xt_entry_match *m, struct net *net) 
static int

check_entry(const struct ip6t_entry *e)

{

	const struct xt_entry_target *t;



	if (!ip6_checkentry(&e->ipv6))

		return -EINVAL;



	if (e->target_offset + sizeof(struct xt_entry_target) >

	    e->next_offset)

		return -EINVAL;



	t = ip6t_get_target_c(e);

	if (e->target_offset + t->u.target_size > e->next_offset)

		return -EINVAL;



	return 0;

	return xt_check_entry_offsets(e, e->target_offset, e->next_offset);

}



static int check_match(struct xt_entry_match *m, struct xt_mtchk_param *par)

net/netfilter/x_tables.c

+34 −0
Original line number Diff line number Diff line
@@ -541,6 +541,40 @@ int xt_compat_match_to_user(const struct xt_entry_match *m, 
EXPORT_SYMBOL_GPL(xt_compat_match_to_user);

#endif /* CONFIG_COMPAT */



/**

 * xt_check_entry_offsets - validate arp/ip/ip6t_entry

 *

 * @base: pointer to arp/ip/ip6t_entry

 * @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.

 *

 * 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

 *   length.

 *

 * Return: 0 on success, negative errno on failure.

 */

int xt_check_entry_offsets(const void *base,

			   unsigned int target_offset,

			   unsigned int next_offset)

{

	const struct xt_entry_target *t;

	const char *e = base;



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

		return -EINVAL;



	t = (void *)(e + target_offset);

	if (target_offset + t->u.target_size > next_offset)

		return -EINVAL;



	return 0;

}

EXPORT_SYMBOL(xt_check_entry_offsets);



int xt_check_target(struct xt_tgchk_param *par,

		    unsigned int size, u_int8_t proto, bool inv_proto)

{

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