| From 7d35812c3214afa5b37a675113555259cfd67b98 Mon Sep 17 00:00:00 2001 |
| From: Florian Westphal <fw@strlen.de> |
| Date: Fri, 1 Apr 2016 14:17:23 +0200 |
| Subject: netfilter: x_tables: add and use xt_check_entry_offsets |
| |
| From: Florian Westphal <fw@strlen.de> |
| |
| commit 7d35812c3214afa5b37a675113555259cfd67b98 upstream. |
| |
| 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: Florian Westphal <fw@strlen.de> |
| Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org> |
| Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
| |
| --- |
| include/linux/netfilter/x_tables.h | 4 ++++ |
| net/ipv4/netfilter/arp_tables.c | 11 +---------- |
| net/ipv4/netfilter/ip_tables.c | 12 +----------- |
| net/ipv6/netfilter/ip6_tables.c | 12 +----------- |
| net/netfilter/x_tables.c | 34 ++++++++++++++++++++++++++++++++++ |
| 5 files changed, 41 insertions(+), 32 deletions(-) |
| |
| --- a/include/linux/netfilter/x_tables.h |
| +++ b/include/linux/netfilter/x_tables.h |
| @@ -239,6 +239,10 @@ void xt_unregister_match(struct xt_match |
| 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, |
| --- a/net/ipv4/netfilter/arp_tables.c |
| +++ b/net/ipv4/netfilter/arp_tables.c |
| @@ -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) |
| --- a/net/ipv4/netfilter/ip_tables.c |
| +++ b/net/ipv4/netfilter/ip_tables.c |
| @@ -590,20 +590,10 @@ static void cleanup_match(struct xt_entr |
| 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 |
| --- a/net/ipv6/netfilter/ip6_tables.c |
| +++ b/net/ipv6/netfilter/ip6_tables.c |
| @@ -602,20 +602,10 @@ static void cleanup_match(struct xt_entr |
| 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) |
| --- a/net/netfilter/x_tables.c |
| +++ b/net/netfilter/x_tables.c |
| @@ -540,6 +540,40 @@ int xt_compat_match_to_user(const struct |
| 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) |
| { |