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Message-Id: <1461332394-3994-9-git-send-email-pablo@netfilter.org>
Date: Fri, 22 Apr 2016 15:39:39 +0200
From: Pablo Neira Ayuso <pablo@...filter.org>
To: netfilter-devel@...r.kernel.org
Cc: davem@...emloft.net, netdev@...r.kernel.org
Subject: [PATCH 08/23] netfilter: x_tables: check for bogus target offset
From: Florian Westphal <fw@...len.de>
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: Florian Westphal <fw@...len.de>
Signed-off-by: Pablo Neira Ayuso <pablo@...filter.org>
---
include/linux/netfilter/x_tables.h | 4 ++--
net/ipv4/netfilter/arp_tables.c | 5 +++--
net/ipv4/netfilter/ip_tables.c | 5 +++--
net/ipv6/netfilter/ip6_tables.c | 5 +++--
net/netfilter/x_tables.c | 17 +++++++++++++++--
5 files changed, 26 insertions(+), 10 deletions(-)
diff --git a/include/linux/netfilter/x_tables.h b/include/linux/netfilter/x_tables.h
index 08de48b..30cfb1e 100644
--- a/include/linux/netfilter/x_tables.h
+++ b/include/linux/netfilter/x_tables.h
@@ -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);
diff --git a/net/ipv4/netfilter/arp_tables.c b/net/ipv4/netfilter/arp_tables.c
index ab8952a..95ed4e4 100644
--- a/net/ipv4/netfilter/arp_tables.c
+++ b/net/ipv4/netfilter/arp_tables.c
@@ -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;
diff --git a/net/ipv4/netfilter/ip_tables.c b/net/ipv4/netfilter/ip_tables.c
index 7d24c87..baab033d 100644
--- a/net/ipv4/netfilter/ip_tables.c
+++ b/net/ipv4/netfilter/ip_tables.c
@@ -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;
diff --git a/net/ipv6/netfilter/ip6_tables.c b/net/ipv6/netfilter/ip6_tables.c
index 73eee7b..6957627 100644
--- a/net/ipv6/netfilter/ip6_tables.c
+++ b/net/ipv6/netfilter/ip6_tables.c
@@ -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;
diff --git a/net/netfilter/x_tables.c b/net/netfilter/x_tables.c
index 1cb7a27..e2a6f2a 100644
--- a/net/netfilter/x_tables.c
+++ b/net/netfilter/x_tables.c
@@ -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;
--
2.1.4
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