[PATCH 5.9 02/74] netfilter: nftables_offload: KASAN slab-out-of-bounds Read in nft_flow_rule_create

Greg Kroah-Hartman
2020-10-31T11:43:53Z

From: Saeed Mirzamohammadi <saeed.mirzamohammadi@oracle.com>

commit 31cc578ae2de19c748af06d859019dced68e325d upstream.

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: Saeed Mirzamohammadi <saeed.mirzamohammadi@oracle.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
include/net/netfilter/nf_tables.h | 6 ++++++
net/netfilter/nf_tables_api.c | 6 +++---
net/netfilter/nf_tables_offload.c | 4 ++--
3 files changed, 11 insertions(+), 5 deletions(-)

--- a/include/net/netfilter/nf_tables.h
+++ b/include/net/netfilter/nf_tables.h
@@ -896,6 +896,12 @@ static inline struct nft_expr *nft_expr_
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];
--- a/net/netfilter/nf_tables_api.c
+++ b/net/netfilter/nf_tables_api.c
@@ -302,7 +302,7 @@ static void nft_rule_expr_activate(const
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(con
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);

@@ -3036,7 +3036,7 @@ static void nf_tables_rule_destroy(const
* 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;
--- a/net/netfilter/nf_tables_offload.c
+++ b/net/netfilter/nf_tables_offload.c
@@ -37,7 +37,7 @@ struct nft_flow_rule *nft_flow_rule_crea
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_crea
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;