[PATCH AUTOSEL 4.19 70/81] netfilter: nf_tables: use-after-free in dynamic operations

Sasha Levin
2019-05-07T05:55:33Z

From: Pablo Neira Ayuso <pablo@netfilter.org>

[ Upstream commit 3f3a390dbd59d236f62cff8e8b20355ef7069e3d ]

Smatch reports:

net/netfilter/nf_tables_api.c:2167 nf_tables_expr_destroy()
error: dereferencing freed memory 'expr->ops'

net/netfilter/nf_tables_api.c
2162 static void nf_tables_expr_destroy(const struct nft_ctx *ctx,
2163 struct nft_expr *expr)
2164 {
2165 if (expr->ops->destroy)
2166 expr->ops->destroy(ctx, expr);
^^^^
--> 2167 module_put(expr->ops->type->owner);
^^^^^^^^^
2168 }

Smatch says there are three functions which free expr->ops.

Fixes: b8e204006340 ("netfilter: nft_compat: use .release_ops and remove list of extension")
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
---
net/netfilter/nf_tables_api.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/net/netfilter/nf_tables_api.c b/net/netfilter/nf_tables_api.c
index f272f9538c44..ef7ff13a7b99 100644
--- a/net/netfilter/nf_tables_api.c
+++ b/net/netfilter/nf_tables_api.c
@@ -2113,9 +2113,11 @@ static int nf_tables_newexpr(const struct nft_ctx *ctx,
static void nf_tables_expr_destroy(const struct nft_ctx *ctx,
struct nft_expr *expr)
{
+ const struct nft_expr_type *type = expr->ops->type;
+
if (expr->ops->destroy)
expr->ops->destroy(ctx, expr);
- module_put(expr->ops->type->owner);
+ module_put(type->owner);
}

struct nft_expr *nft_expr_init(const struct nft_ctx *ctx,
--
2.20.1