ruleset: fix crash if we free sets included in the set_list

PATCH Applied Alvaro Neira Ayuso 2 participants 4 messages Feb 24, 2015 netfilter

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Alvaro Neira Ayuso

author

2015-02-24 08:10 UTC #0 lore raw

PATCH v3 1/1 ruleset: fix crash if we free sets included in the set_list

When we parse a ruleset which has a rule using a set. First step is parse the set, set up an id and add it to a set list. Later, we use this set list to find the set associated to the rule and we set up the set id to the expression (lookup expression) of the rule.

The problem is if we return this set using the function nft_ruleset_parse_file_cb and we free this set. We have a crash when we try to iterate in the set list.

This patch solves it, cloning the set and adding the new set to the set list.

Signed-off-by Alvaro Neira Ayuso <[email protected]>

---
[changes in v3]
* Use memcpy to clone the object.

 include/libnftnl/set.h |    2 ++
 src/ruleset.c          |    7 ++++++-
 src/set.c              |   31 +++++++++++++++++++++++++++++++
 src/set_elem.c         |   16 ++++++++++++++++
 4 files changed, 55 insertions(+), 1 deletion(-)

include/libnftnl/set.h +2 -0

index 7f3504f..3f8ef87 100644
@@ -42,6 +42,7 @@ const void *nft_set_attr_get_data(struct nft_set *s, uint16_t attr,
 				  uint32_t *data_len);
 const char *nft_set_attr_get_str(struct nft_set *s, uint16_t attr);
 uint32_t nft_set_attr_get_u32(struct nft_set *s, uint16_t attr);
+struct nft_set *nft_set_clone(const struct nft_set *set);
 
 struct nlmsghdr;

@@ -103,6 +104,7 @@ const char *nft_set_elem_attr_get_str(struct nft_set_elem *s, uint16_t attr);
 uint32_t nft_set_elem_attr_get_u32(struct nft_set_elem *s, uint16_t attr);
 
 bool nft_set_elem_attr_is_set(const struct nft_set_elem *s, uint16_t attr);
+struct nft_set_elem *nft_set_elem_clone(struct nft_set_elem *elem);
 
 #define nft_set_elem_nlmsg_build_hdr	nft_nlmsg_build_hdr
 void nft_set_elems_nlmsg_build_payload(struct nlmsghdr *nlh, struct nft_set *s);

src/ruleset.c +6 -1

index 89ea344..9e8965c 100644
@@ -312,9 +312,14 @@ static int nft_ruleset_parse_set(struct nft_parse_ctx *ctx,
 				 struct nft_set *set, uint32_t type,
 				 struct nft_parse_err *err)
 {
+	struct nft_set *newset;
+
 	nft_set_attr_set_u32(set, NFT_SET_ATTR_ID, ctx->set_id++);
-	nft_set_list_add_tail(set, ctx->set_list);
+	newset = nft_set_clone(set);
+	if (newset == NULL)
+		goto err;
 
+	nft_set_list_add_tail(newset, ctx->set_list);
 	nft_ruleset_ctx_set_u32(ctx, NFT_RULESET_CTX_TYPE, type);
 	nft_ruleset_ctx_set(ctx, NFT_RULESET_CTX_SET, set);
 	if (ctx->cb(ctx) < 0)

src/set.c +31 -0

index c6c3301..a02189b 100644
@@ -249,6 +249,37 @@ uint32_t nft_set_attr_get_u32(struct nft_set *s, uint16_t attr)
 }
 EXPORT_SYMBOL(nft_set_attr_get_u32);
 
+struct nft_set *nft_set_clone(const struct nft_set *set)
+{
+	struct nft_set *newset;
+	struct nft_set_elem *elem, *newelem;
+
+	newset = nft_set_alloc();
+	if (newset == NULL)
+		return NULL;
+
+	memcpy(newset, set, sizeof(*set));
+
+	if (set->flags & (1 << NFT_SET_ATTR_TABLE))
+		newset->table = strdup(set->table);
+	if (set->flags & (1 << NFT_SET_ATTR_NAME))
+		newset->name = strdup(set->name);
+
+	INIT_LIST_HEAD(&newset->element_list);
+	list_for_each_entry(elem, &set->element_list, head) {
+		newelem = nft_set_elem_clone(elem);
+		if (newelem == NULL)
+			goto err;
+
+		list_add_tail(&newelem->head, &newset->element_list);
+	}
+
+	return newset;
+err:
+	nft_set_free(newset);
+	return NULL;
+}
+
 static void
 nft_set_nlmsg_build_desc_payload(struct nlmsghdr *nlh, struct nft_set *s)
 {

src/set_elem.c +16 -0

index 5794f3a..47ea1c5 100644
@@ -164,6 +164,22 @@ uint32_t nft_set_elem_attr_get_u32(struct nft_set_elem *s, uint16_t attr)
 }
 EXPORT_SYMBOL(nft_set_elem_attr_get_u32);
 
+struct nft_set_elem *nft_set_elem_clone(struct nft_set_elem *elem)
+{
+	struct nft_set_elem *newelem;
+
+	newelem = nft_set_elem_alloc();
+	if (newelem == NULL)
+		return NULL;
+
+	memcpy(newelem, elem, sizeof(*elem));
+
+	if (elem->flags & (1 << NFT_SET_ELEM_ATTR_CHAIN))
+		newelem->data.chain = strdup(elem->data.chain);
+
+	return newelem;
+}
+
 void nft_set_elem_nlmsg_build_payload(struct nlmsghdr *nlh,
 				      struct nft_set_elem *e)
 {

Signature · 1 line

1.7.10.4

Alvaro Neira Ayuso

author

2015-02-24 08:10 UTC #1 lore raw

PATCH 1/1 ruleset: crash in path error when we build the xml tree

Crash when we try to release a tree that is not initialized.

Signed-off-by Alvaro Neira Ayuso <[email protected]>

---
 src/ruleset.c |    6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

src/ruleset.c +4 -2

index 9e8965c..8549130 100644
@@ -669,8 +669,10 @@ static int nft_ruleset_xml_parse(const void *xml, struct nft_parse_err *err,
 		nft_ruleset_ctx_set(&ctx, NFT_RULESET_CTX_DATA, arg);
 
 	tree = nft_mxml_build_tree(xml, "nftables", err, input);
-	if (tree == NULL)
-		goto err;
+	if (tree == NULL) {
+		nft_set_list_free(ctx.set_list);
+		return -1;
+	}
 
 	ctx.xml = tree;

Signature · 1 line

1.7.10.4

Pablo Neira Ayuso

maintainer

2015-02-24 13:40 UTC #2 lore raw

Re: [libnftnl PATCH] ruleset: crash in path error when we build the xml tree

Quoted 12 lines · Alvaro Neira Ayuso

Crash when we try to release a tree that is not initialized.
Signed-off-by Alvaro Neira Ayuso <[email protected]>
---
 src/ruleset.c |    6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)
src/ruleset.c +0 -0
index 9e8965c..8549130 100644

src/ruleset.c static int nft_ruleset_xml_parse(const void *xml, struct nft_parse_err *err, · line 675

Quoted 9 lines

src/ruleset.c +4 -2

@@ -669,8 +669,10 @@ static int nft_ruleset_xml_parse(const void *xml, struct nft_parse_err *err,
 		nft_ruleset_ctx_set(&ctx, NFT_RULESET_CTX_DATA, arg);
 
 	tree = nft_mxml_build_tree(xml, "nftables", err, input);
-	if (tree == NULL)
-		goto err;
+	if (tree == NULL) {
+		nft_set_list_free(ctx.set_list);
+		return -1;
+	}

You have exactly the same problem in nft_ruleset_json_parse().

Have a look at the patch attached, it provides a template on how to fix this.

Another different thing: it would be good to use the new 'buffer' class to snprintf the ruleset.

src/ruleset.c +5 -4

index 89ea344..86d8033 100644
@@ -665,7 +665,7 @@ static int nft_ruleset_xml_parse(const void *xml, struct nft_parse_err *err,
 
 	tree = nft_mxml_build_tree(xml, "nftables", err, input);
 	if (tree == NULL)
-		goto err;
+		goto err1;
 
 	ctx.xml = tree;

@@ -673,16 +673,17 @@ static int nft_ruleset_xml_parse(const void *xml, struct nft_parse_err *err,
 	while (nodecmd != NULL) {
 		cmd = nodecmd->value.opaque;
 		if (nft_ruleset_xml_parse_cmd(cmd, err, &ctx) < 0)
-			goto err;
+			goto err2;
 		nodecmd = mxmlWalkNext(tree, tree, MXML_NO_DESCEND);
 	}
 
 	nft_set_list_free(ctx.set_list);
 	mxmlDelete(tree);
 	return 0;
-err:
-	nft_set_list_free(ctx.set_list);
+err2:
 	mxmlDelete(tree);
+err1:
+	nft_set_list_free(ctx.set_list);
 	return -1;
 #else
 	errno = EOPNOTSUPP;

Pablo Neira Ayuso

maintainer Applied

2015-02-24 13:44 UTC #3 lore raw

In reply to Alvaro Neira Ayuso

Quoted 10 lines · Alvaro Neira Ayuso

When we parse a ruleset which has a rule using a set. First step is parse the set, set up an id and add it to a set list. Later, we use this set list to find the set associated to the rule and we set up the set id to the expression (lookup expression) of the rule.
The problem is if we return this set using the function nft_ruleset_parse_file_cb and we free this set. We have a crash when we try to iterate in the set list.
This patch solves it, cloning the set and adding the new set to the set list.

Applied, thanks.