From 3f3a390dbd59d236f62cff8e8b20355ef7069e3d Mon Sep 17 00:00:00 2001 From: Pablo Neira Ayuso Date: Mon, 11 Mar 2019 13:04:16 +0100 Subject: [PATCH] netfilter: nf_tables: use-after-free in dynamic operations 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 Signed-off-by: Pablo Neira Ayuso --- 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,