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Patch "netfilter: x_tables: add and use xt_check_entry_offsets" has been added to the 4.6-stable tree

PATCH [email protected] 1 participant 1 message Jun 22, 2016

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This is a note to let you know that I've just added the patch titled

netfilter: x_tables: add and use xt_check_entry_offsets

to the 4.6-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
netfilter-x_tables-add-and-use-xt_check_entry_offsets.patch
and it can be found in the queue-4.6 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

Quoted 1 line

From 7d35812c3214afa5b37a675113555259cfd67b98 Mon Sep 17 00:00:00 2001

From: Florian Westphal <[email protected]>
Date: Fri, 1 Apr 2016 14:17:23 +0200
Subject: netfilter: x_tables: add and use xt_check_entry_offsets

From: Florian Westphal <[email protected]>

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 <[email protected]>
Signed-off-by Pablo Neira Ayuso <[email protected]>
Signed-off-by Greg Kroah-Hartman <[email protected]>
---
 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(-)
include/linux/netfilter/x_tables.h +4 -0
@@ -242,6 +242,10 @@ 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,
net/ipv4/netfilter/arp_tables.c +1 -10
@@ -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
@@ -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
net/ipv6/netfilter/ip6_tables.c +1 -11
@@ -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)
net/netfilter/x_tables.c +34 -0
@@ -541,6 +541,40 @@ 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)
 {

Patches currently in stable-queue which might be from [email protected] are

queue-4.6/netfilter-x_tables-add-and-use-xt_check_entry_offsets.patch queue-4.6/netfilter-x_tables-assert-minimum-target-size.patch queue-4.6/netfilter-x_tables-add-compat-version-of-xt_check_entry_offsets.patch queue-4.6/netfilter-x_tables-check-for-bogus-target-offset.patch queue-4.6/netfilter-x_tables-validate-targets-of-jumps.patch queue-4.6/netfilter-x_tables-don-t-move-to-non-existent-next-rule.patch queue-4.6/netfilter-x_tables-kill-check_entry-helper.patch queue-4.6/netfilter-x_tables-check-standard-target-size-too.patch queue-4.6/netfilter-x_tables-validate-all-offsets-and-sizes-in-a-rule.patch