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Patch "netfilter: x_tables: check for bogus target offset" has been added to the 4.4-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: check for bogus target offset

to the 4.4-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-check-for-bogus-target-offset.patch
and it can be found in the queue-4.4 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 ce683e5f9d045e5d67d1312a42b359cb2ab2a13c Mon Sep 17 00:00:00 2001

From: Florian Westphal <[email protected]>
Date: Fri, 1 Apr 2016 14:17:28 +0200
Subject: netfilter: x_tables: check for bogus target offset

From: Florian Westphal <[email protected]>

commit ce683e5f9d045e5d67d1312a42b359cb2ab2a13c upstream.

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 <[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    |    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(-)
include/linux/netfilter/x_tables.h +2 -2
@@ -239,7 +239,7 @@ 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,
+int xt_check_entry_offsets(const void *base, const char *elems,
 			   unsigned int target_offset,
 			   unsigned int next_offset);
 

@@ -492,7 +492,7 @@ void xt_compat_target_from_user(struct x
 				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
@@ -592,7 +592,8 @@ static inline int check_entry_size_and_h
 	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;
 

@@ -1253,7 +1254,7 @@ check_compat_entry_size_and_hooks(struct
 	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
@@ -754,7 +754,8 @@ check_entry_size_and_hooks(struct ipt_en
 	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;
 

@@ -1512,7 +1513,7 @@ check_compat_entry_size_and_hooks(struct
 	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
@@ -766,7 +766,8 @@ check_entry_size_and_hooks(struct ip6t_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;
 

@@ -1524,7 +1525,7 @@ check_compat_entry_size_and_hooks(struct
 	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
@@ -545,14 +545,17 @@ 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;
 

@@ -576,12 +579,16 @@ EXPORT_SYMBOL(xt_compat_check_entry_offs
  * 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

@@ -590,12 +597,18 @@ EXPORT_SYMBOL(xt_compat_check_entry_offs
  * 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;

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

queue-4.4/netfilter-x_tables-add-and-use-xt_check_entry_offsets.patch queue-4.4/netfilter-x_tables-assert-minimum-target-size.patch queue-4.4/netfilter-x_tables-add-compat-version-of-xt_check_entry_offsets.patch queue-4.4/netfilter-x_tables-check-for-bogus-target-offset.patch queue-4.4/netfilter-x_tables-validate-e-target_offset-early.patch queue-4.4/netfilter-x_tables-validate-targets-of-jumps.patch queue-4.4/netfilter-x_tables-don-t-move-to-non-existent-next-rule.patch queue-4.4/netfilter-x_tables-kill-check_entry-helper.patch queue-4.4/netfilter-x_tables-make-sure-e-next_offset-covers-remaining-blob-size.patch queue-4.4/netfilter-x_tables-check-standard-target-size-too.patch queue-4.4/netfilter-x_tables-validate-all-offsets-and-sizes-in-a-rule.patch queue-4.4/netfilter-x_tables-fix-unconditional-helper.patch