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netfilter: nftables_offload: KASAN slab-out-of-bounds Read in nft_flow_rule_create

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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>
This commit is contained in:
Saeed Mirzamohammadi 2020-10-20 13:41:36 +02:00 committed by Pablo Neira Ayuso
parent 64747d5ed1
commit 31cc578ae2
3 changed files with 11 additions and 5 deletions
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6
include/net/netfilter/nf_tables.h
View File

@ -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]; 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) static inline struct nft_userdata *nft_userdata(const struct nft_rule *rule)
{ {
return (void *)&rule->data[rule->dlen]; return (void *)&rule->data[rule->dlen];

6
net/netfilter/nf_tables_api.c
View File

@ -302,7 +302,7 @@ static void nft_rule_expr_activate(const struct nft_ctx *ctx,
struct nft_expr *expr; struct nft_expr *expr;
expr = nft_expr_first(rule); expr = nft_expr_first(rule);
while (expr != nft_expr_last(rule) && expr->ops) { while (nft_expr_more(rule, expr)) {
if (expr->ops->activate) if (expr->ops->activate)
expr->ops->activate(ctx, expr); expr->ops->activate(ctx, expr);
@ -317,7 +317,7 @@ static void nft_rule_expr_deactivate(const struct nft_ctx *ctx,
struct nft_expr *expr; struct nft_expr *expr;
expr = nft_expr_first(rule); expr = nft_expr_first(rule);
while (expr != nft_expr_last(rule) && expr->ops) { while (nft_expr_more(rule, expr)) {
if (expr->ops->deactivate) if (expr->ops->deactivate)
expr->ops->deactivate(ctx, expr, phase); 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(). * is called on error from nf_tables_newrule().
*/ */
expr = nft_expr_first(rule); expr = nft_expr_first(rule);
while (expr != nft_expr_last(rule) && expr->ops) { while (nft_expr_more(rule, expr)) {
next = nft_expr_next(expr); next = nft_expr_next(expr);
nf_tables_expr_destroy(ctx, expr); nf_tables_expr_destroy(ctx, expr);
expr = next; expr = next;

4
net/netfilter/nf_tables_offload.c
View File

@ -37,7 +37,7 @@ struct nft_flow_rule *nft_flow_rule_create(struct net *net,
struct nft_expr *expr; struct nft_expr *expr;
expr = nft_expr_first(rule); 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) if (expr->ops->offload_flags & NFT_OFFLOAD_F_ACTION)
num_actions++; num_actions++;
@ -61,7 +61,7 @@ struct nft_flow_rule *nft_flow_rule_create(struct net *net,
ctx->net = net; ctx->net = net;
ctx->dep.type = NFT_OFFLOAD_DEP_UNSPEC; 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) { if (!expr->ops->offload) {
err = -EOPNOTSUPP; err = -EOPNOTSUPP;
goto err_out; goto err_out;