Commit 31cc578a authored by Saeed Mirzamohammadi's avatar Saeed Mirzamohammadi Committed by Pablo Neira Ayuso
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netfilter: nftables_offload: KASAN slab-out-of-bounds Read in nft_flow_rule_create 



This patch fixes the issue due to:

BUG: KASAN: slab-out-of-bounds in nft_flow_rule_create+0x622/0x6a2
net/netfilter/nf_tables_offload.c:40
Read of size 8 at addr ffff888103910b58 by task syz-executor227/16244

The error happens when expr->ops is accessed early on before performing the boundary check and after nft_expr_next() moves the expr to go out-of-bounds.

This patch checks the boundary condition before expr->ops that fixes the slab-out-of-bounds Read issue.

Add nft_expr_more() and use it to fix this problem.

Signed-off-by: default avatarSaeed Mirzamohammadi <saeed.mirzamohammadi@oracle.com>
Signed-off-by: default avatarPablo Neira Ayuso <pablo@netfilter.org>
parent 64747d5e

include/net/netfilter/nf_tables.h

+6 −0
Original line number Diff line number Diff line
@@ -891,6 +891,12 @@ static inline struct nft_expr *nft_expr_last(const struct nft_rule *rule) 
	return (struct nft_expr *)&rule->data[rule->dlen];

}



static inline bool nft_expr_more(const struct nft_rule *rule,

				 const struct nft_expr *expr)

{

	return expr != nft_expr_last(rule) && expr->ops;

}



static inline struct nft_userdata *nft_userdata(const struct nft_rule *rule)

{

	return (void *)&rule->data[rule->dlen];

net/netfilter/nf_tables_api.c

+3 −3
Original line number Diff line number Diff line
@@ -302,7 +302,7 @@ static void nft_rule_expr_activate(const struct nft_ctx *ctx, 
	struct nft_expr *expr;



	expr = nft_expr_first(rule);

	while (expr != nft_expr_last(rule) && expr->ops) {

	while (nft_expr_more(rule, expr)) {

		if (expr->ops->activate)

			expr->ops->activate(ctx, expr);
@@ -317,7 +317,7 @@ static void nft_rule_expr_deactivate(const struct nft_ctx *ctx, 
	struct nft_expr *expr;



	expr = nft_expr_first(rule);

	while (expr != nft_expr_last(rule) && expr->ops) {

	while (nft_expr_more(rule, expr)) {

		if (expr->ops->deactivate)

			expr->ops->deactivate(ctx, expr, phase);
@@ -3080,7 +3080,7 @@ static void nf_tables_rule_destroy(const struct nft_ctx *ctx, 
	 * is called on error from nf_tables_newrule().

	 */

	expr = nft_expr_first(rule);

	while (expr != nft_expr_last(rule) && expr->ops) {

	while (nft_expr_more(rule, expr)) {

		next = nft_expr_next(expr);

		nf_tables_expr_destroy(ctx, expr);

		expr = next;

net/netfilter/nf_tables_offload.c

+2 −2
Original line number Diff line number Diff line
@@ -37,7 +37,7 @@ struct nft_flow_rule *nft_flow_rule_create(struct net *net, 
	struct nft_expr *expr;



	expr = nft_expr_first(rule);

	while (expr->ops && expr != nft_expr_last(rule)) {

	while (nft_expr_more(rule, expr)) {

		if (expr->ops->offload_flags & NFT_OFFLOAD_F_ACTION)

			num_actions++;
@@ -61,7 +61,7 @@ struct nft_flow_rule *nft_flow_rule_create(struct net *net, 
	ctx->net = net;

	ctx->dep.type = NFT_OFFLOAD_DEP_UNSPEC;



	while (expr->ops && expr != nft_expr_last(rule)) {

	while (nft_expr_more(rule, expr)) {

		if (!expr->ops->offload) {

			err = -EOPNOTSUPP;

			goto err_out;

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