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From: Pablo Neira Ayuso <pablo@netfilter.org>
To: netfilter-devel@vger.kernel.org
Cc: davem@davemloft.net, netdev@vger.kernel.org
Subject: [PATCH 4/5] netfilter: nf_tables: use-after-free in dynamic operations
Date: Mon, 11 Mar 2019 23:50:34 +0100
Message-ID: <20190311225035.21250-5-pablo@netfilter.org> (raw)
In-Reply-To: <20190311225035.21250-1-pablo@netfilter.org>

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>
---
 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 ca09ef037ca5..9d8f51dfc593 100644
--- a/net/netfilter/nf_tables_api.c
+++ b/net/netfilter/nf_tables_api.c
@@ -2162,9 +2162,11 @@ 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,
-- 
2.11.0


  parent reply index

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-03-11 22:50 [PATCH 0/5] Netfilter fixes for net Pablo Neira Ayuso
2019-03-11 22:50 ` [PATCH 1/5] netfilter: nat: don't register device notifier twice Pablo Neira Ayuso
2019-03-11 22:50 ` [PATCH 2/5] netfilter: nf_tables: fix set double-free in abort path Pablo Neira Ayuso
2019-03-11 22:50 ` [PATCH 3/5] netfilter: nf_tables: bogus EBUSY when deleting set after flush Pablo Neira Ayuso
2019-03-11 22:50 ` Pablo Neira Ayuso [this message]
2019-03-11 22:50 ` [PATCH 5/5] netfilter: nf_tables: return immediately on empty commit Pablo Neira Ayuso
2019-03-11 23:14 ` [PATCH 0/5] Netfilter fixes for net David Miller

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