[PATCH] NETFILTER: Missed and reordered checks in {arp,ip,ip6}_tables

Backport fix for missing ruleset validation in {arp,ip,ip6}_tables
and a fix on top which fixes a regression in the first patch.

There is a number of issues in parsing user-provided table in
translate_table(). Malicious user with CAP_NET_ADMIN may crash system by
passing special-crafted table to the *_tables.

The first issue is that mark_source_chains() function is called before entry
content checks. In case of standard target, mark_source_chains() function
uses t->verdict field in order to determine new position. But the check, that
this field leads no further, than the table end, is in check_entry(), which
is called later, than mark_source_chains().

The second issue, that there is no check that target_offset points inside
entry. If so, *_ITERATE_MATCH macro will follow further, than the entry
ends. As a result, we'll have oops or memory disclosure.

And the third issue, that there is no check that the target is completely
inside entry. Results are the same, as in previous issue.

Upstream commit 590bdf7fd2292b47c428111cb1360e312eff207e introduced a
regression in match/target hook validation. mark_source_chains builds
a bitmask for each rule representing the hooks it can be reached from,
which is then used by the matches and targets to make sure they are
only called from valid hooks. The patch moved the match/target specific
validation before the mark_source_chains call, at which point the mask
is always zero.

This patch returns back to the old order and moves the standard checks
to mark_source_chains. This allows to get rid of a special case for
standard targets as a nice side-effect.

Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: Chris Wright <chrisw@sous-sol.org>

3 files changed, 77 insertions, 78 deletions

diff --git a/net/ipv4/netfilter/arp_tables.c b/net/ipv4/netfilter/arp_tables.c
index 8d1d7a6e72a5..aa8465caeb33 100644
--- a/net/ipv4/netfilter/arp_tables.c
+++ b/net/ipv4/netfilter/arp_tables.c
@@ -380,6 +380,13 @@ static int mark_source_chains(struct xt_table_info *newinfo,
 			    && unconditional(&e->arp)) {
 				unsigned int oldpos, size;
 
+				if (t->verdict < -NF_MAX_VERDICT - 1) {
+					duprintf("mark_source_chains: bad "
+						"negative verdict (%i)\n",
+								t->verdict);
+					return 0;
+				}
+
 				/* Return: backtrack through the last
 				 * big jump.
 				 */
@@ -409,6 +416,14 @@ static int mark_source_chains(struct xt_table_info *newinfo,
 				if (strcmp(t->target.u.user.name,
 					   ARPT_STANDARD_TARGET) == 0
 				    && newpos >= 0) {
+					if (newpos > newinfo->size -
+						sizeof(struct arpt_entry)) {
+						duprintf("mark_source_chains: "
+							"bad verdict (%i)\n",
+								newpos);
+						return 0;
+					}
+
 					/* This a jump; chase it. */
 					duprintf("Jump rule %u -> %u\n",
 						 pos, newpos);
@@ -431,8 +446,6 @@ static int mark_source_chains(struct xt_table_info *newinfo,
 static inline int standard_check(const struct arpt_entry_target *t,
 				 unsigned int max_offset)
 {
-	struct arpt_standard_target *targ = (void *)t;
-
 	/* Check standard info. */
 	if (t->u.target_size
 	    != ARPT_ALIGN(sizeof(struct arpt_standard_target))) {
@@ -442,18 +455,6 @@ static inline int standard_check(const struct arpt_entry_target *t,
 		return 0;
 	}
 
-	if (targ->verdict >= 0
-	    && targ->verdict > max_offset - sizeof(struct arpt_entry)) {
-		duprintf("arpt_standard_check: bad verdict (%i)\n",
-			 targ->verdict);
-		return 0;
-	}
-
-	if (targ->verdict < -NF_MAX_VERDICT - 1) {
-		duprintf("arpt_standard_check: bad negative verdict (%i)\n",
-			 targ->verdict);
-		return 0;
-	}
 	return 1;
 }
 
@@ -471,7 +472,13 @@ static inline int check_entry(struct arpt_entry *e, const char *name, unsigned i
 		return -EINVAL;
 	}
 
+	if (e->target_offset + sizeof(struct arpt_entry_target) > e->next_offset)
+		return -EINVAL;
+
 	t = arpt_get_target(e);
+	if (e->target_offset + t->u.target_size > e->next_offset)
+		return -EINVAL;
+
 	target = try_then_request_module(xt_find_target(NF_ARP, t->u.user.name,
 							t->u.user.revision),
 					 "arpt_%s", t->u.user.name);
@@ -641,7 +648,7 @@ static int translate_table(const char *name,
 
 	if (ret != 0) {
 		ARPT_ENTRY_ITERATE(entry0, newinfo->size,
-				   cleanup_entry, &i);
+				cleanup_entry, &i);
 		return ret;
 	}
 
diff --git a/net/ipv4/netfilter/ip_tables.c b/net/ipv4/netfilter/ip_tables.c
index b22e4d31f291..e96443699361 100644
--- a/net/ipv4/netfilter/ip_tables.c
+++ b/net/ipv4/netfilter/ip_tables.c
@@ -404,6 +404,13 @@ mark_source_chains(struct xt_table_info *newinfo,
 			    && unconditional(&e->ip)) {
 				unsigned int oldpos, size;
 
+				if (t->verdict < -NF_MAX_VERDICT - 1) {
+					duprintf("mark_source_chains: bad "
+						"negative verdict (%i)\n",
+								t->verdict);
+					return 0;
+				}
+
 				/* Return: backtrack through the last
 				   big jump. */
 				do {
@@ -441,6 +448,13 @@ mark_source_chains(struct xt_table_info *newinfo,
 				if (strcmp(t->target.u.user.name,
 					   IPT_STANDARD_TARGET) == 0
 				    && newpos >= 0) {
+					if (newpos > newinfo->size -
+						sizeof(struct ipt_entry)) {
+						duprintf("mark_source_chains: "
+							"bad verdict (%i)\n",
+								newpos);
+						return 0;
+					}
 					/* This a jump; chase it. */
 					duprintf("Jump rule %u -> %u\n",
 						 pos, newpos);
@@ -474,27 +488,6 @@ cleanup_match(struct ipt_entry_match *m, unsigned int *i)
 }
 
 static inline int
-standard_check(const struct ipt_entry_target *t,
-	       unsigned int max_offset)
-{
-	struct ipt_standard_target *targ = (void *)t;
-
-	/* Check standard info. */
-	if (targ->verdict >= 0
-	    && targ->verdict > max_offset - sizeof(struct ipt_entry)) {
-		duprintf("ipt_standard_check: bad verdict (%i)\n",
-			 targ->verdict);
-		return 0;
-	}
-	if (targ->verdict < -NF_MAX_VERDICT - 1) {
-		duprintf("ipt_standard_check: bad negative verdict (%i)\n",
-			 targ->verdict);
-		return 0;
-	}
-	return 1;
-}
-
-static inline int
 check_match(struct ipt_entry_match *m,
 	    const char *name,
 	    const struct ipt_ip *ip,
@@ -552,12 +545,18 @@ check_entry(struct ipt_entry *e, const char *name, unsigned int size,
 		return -EINVAL;
 	}
 
+	if (e->target_offset + sizeof(struct ipt_entry_target) > e->next_offset)
+		return -EINVAL;
+
 	j = 0;
 	ret = IPT_MATCH_ITERATE(e, check_match, name, &e->ip, e->comefrom, &j);
 	if (ret != 0)
 		goto cleanup_matches;
 
 	t = ipt_get_target(e);
+	ret = -EINVAL;
+	if (e->target_offset + t->u.target_size > e->next_offset)
+			goto cleanup_matches;
 	target = try_then_request_module(xt_find_target(AF_INET,
 						     t->u.user.name,
 						     t->u.user.revision),
@@ -575,12 +574,7 @@ check_entry(struct ipt_entry *e, const char *name, unsigned int size,
 	if (ret)
 		goto err;
 
-	if (t->u.kernel.target == &ipt_standard_target) {
-		if (!standard_check(t, size)) {
-			ret = -EINVAL;
-			goto cleanup_matches;
-		}
-	} else if (t->u.kernel.target->checkentry
+	if (t->u.kernel.target->checkentry
 		   && !t->u.kernel.target->checkentry(name, e, target, t->data,
 						      t->u.target_size
 						      - sizeof(*t),
@@ -730,7 +724,7 @@ translate_table(const char *name,
 
 	if (ret != 0) {
 		IPT_ENTRY_ITERATE(entry0, newinfo->size,
-				  cleanup_entry, &i);
+				cleanup_entry, &i);
 		return ret;
 	}
 
@@ -1531,6 +1525,10 @@ check_compat_entry_size_and_hooks(struct ipt_entry *e,
 		return -EINVAL;
 	}
 
+	if (e->target_offset + sizeof(struct compat_xt_entry_target) >
+								e->next_offset)
+		return -EINVAL;
+
 	off = 0;
 	entry_offset = (void *)e - (void *)base;
 	j = 0;
@@ -1540,6 +1538,9 @@ check_compat_entry_size_and_hooks(struct ipt_entry *e,
 		goto cleanup_matches;
 
 	t = ipt_get_target(e);
+	ret = -EINVAL;
+	if (e->target_offset + t->u.target_size > e->next_offset)
+			goto cleanup_matches;
 	target = try_then_request_module(xt_find_target(AF_INET,
 						     t->u.user.name,
 						     t->u.user.revision),
@@ -1656,19 +1657,15 @@ static int compat_copy_entry_from_user(struct ipt_entry *e, void **dstptr,
 	if (ret)
 		goto err;
 
-	ret = -EINVAL;
-	if (t->u.kernel.target == &ipt_standard_target) {
-		if (!standard_check(t, *size))
-			goto err;
-	} else if (t->u.kernel.target->checkentry
+	if (t->u.kernel.target->checkentry
 		   && !t->u.kernel.target->checkentry(name, de, target,
 				t->data, t->u.target_size - sizeof(*t),
 				de->comefrom)) {
 		duprintf("ip_tables: compat: check failed for `%s'.\n",
 			 t->u.kernel.target->name);
+		ret = -EINVAL;
 		goto err;
 	}
-	ret = 0;
  err:
 	return ret;
 }
diff --git a/net/ipv6/netfilter/ip6_tables.c b/net/ipv6/netfilter/ip6_tables.c
index c9d6b23cd3f7..751548a42bf5 100644
--- a/net/ipv6/netfilter/ip6_tables.c
+++ b/net/ipv6/netfilter/ip6_tables.c
@@ -444,6 +444,13 @@ mark_source_chains(struct xt_table_info *newinfo,
 			    && unconditional(&e->ipv6)) {
 				unsigned int oldpos, size;
 
+				if (t->verdict < -NF_MAX_VERDICT - 1) {
+					duprintf("mark_source_chains: bad "
+						"negative verdict (%i)\n",
+								t->verdict);
+					return 0;
+				}
+
 				/* Return: backtrack through the last
 				   big jump. */
 				do {
@@ -481,6 +488,13 @@ mark_source_chains(struct xt_table_info *newinfo,
 				if (strcmp(t->target.u.user.name,
 					   IP6T_STANDARD_TARGET) == 0
 				    && newpos >= 0) {
+					if (newpos > newinfo->size -
+						sizeof(struct ip6t_entry)) {
+						duprintf("mark_source_chains: "
+							"bad verdict (%i)\n",
+								newpos);
+						return 0;
+					}
 					/* This a jump; chase it. */
 					duprintf("Jump rule %u -> %u\n",
 						 pos, newpos);
@@ -514,27 +528,6 @@ cleanup_match(struct ip6t_entry_match *m, unsigned int *i)
 }
 
 static inline int
-standard_check(const struct ip6t_entry_target *t,
-	       unsigned int max_offset)
-{
-	struct ip6t_standard_target *targ = (void *)t;
-
-	/* Check standard info. */
-	if (targ->verdict >= 0
-	    && targ->verdict > max_offset - sizeof(struct ip6t_entry)) {
-		duprintf("ip6t_standard_check: bad verdict (%i)\n",
-			 targ->verdict);
-		return 0;
-	}
-	if (targ->verdict < -NF_MAX_VERDICT - 1) {
-		duprintf("ip6t_standard_check: bad negative verdict (%i)\n",
-			 targ->verdict);
-		return 0;
-	}
-	return 1;
-}
-
-static inline int
 check_match(struct ip6t_entry_match *m,
 	    const char *name,
 	    const struct ip6t_ip6 *ipv6,
@@ -592,12 +585,19 @@ check_entry(struct ip6t_entry *e, const char *name, unsigned int size,
 		return -EINVAL;
 	}
 
+	if (e->target_offset + sizeof(struct ip6t_entry_target) >
+								e->next_offset)
+		return -EINVAL;
+
 	j = 0;
 	ret = IP6T_MATCH_ITERATE(e, check_match, name, &e->ipv6, e->comefrom, &j);
 	if (ret != 0)
 		goto cleanup_matches;
 
 	t = ip6t_get_target(e);
+	ret = -EINVAL;
+	if (e->target_offset + t->u.target_size > e->next_offset)
+			goto cleanup_matches;
 	target = try_then_request_module(xt_find_target(AF_INET6,
 							t->u.user.name,
 							t->u.user.revision),
@@ -615,12 +615,7 @@ check_entry(struct ip6t_entry *e, const char *name, unsigned int size,
 	if (ret)
 		goto err;
 
-	if (t->u.kernel.target == &ip6t_standard_target) {
-		if (!standard_check(t, size)) {
-			ret = -EINVAL;
-			goto cleanup_matches;
-		}
-	} else if (t->u.kernel.target->checkentry
+	if (t->u.kernel.target->checkentry
 		   && !t->u.kernel.target->checkentry(name, e, target, t->data,
 						      t->u.target_size
 						      - sizeof(*t),
@@ -770,7 +765,7 @@ translate_table(const char *name,
 
 	if (ret != 0) {
 		IP6T_ENTRY_ITERATE(entry0, newinfo->size,
-				  cleanup_entry, &i);
+				   cleanup_entry, &i);
 		return ret;
 	}
 
@@ -780,7 +775,7 @@ translate_table(const char *name,
 			memcpy(newinfo->entries[i], entry0, newinfo->size);
 	}
 
-	return ret;
+	return 0;
 }
 
 /* Gets counters. */