diff mbox series

[nf] netfilter: nf_tables: fix use-after-free when deleting compat expressions

Message ID 20181112214345.12513-1-fw@strlen.de
State Accepted
Delegated to: Pablo Neira
Headers show
Series [nf] netfilter: nf_tables: fix use-after-free when deleting compat expressions | expand

Commit Message

Florian Westphal Nov. 12, 2018, 9:43 p.m. UTC 
nft_compat ops do not have static storage duration, unlike all other
expressions.

When nf_tables_expr_destroy() returns, expr->ops might have been
free'd already, so we need to store next address before calling
expression destructor.

For same reason, we can't deref match pointer after nft_xt_put().

This can be easily reproduced by adding msleep() before
nft_match_destroy() returns.

Fixes: 0ca743a55991 ("netfilter: nf_tables: add compatibility layer for x_tables")
Reported-by: Pablo Neira Ayuso <pablo@netfilter.org>
Signed-off-by: Florian Westphal <fw@strlen.de>
---
 net/netfilter/nf_tables_api.c | 5 +++--
 net/netfilter/nft_compat.c    | 3 ++-
 2 files changed, 5 insertions(+), 3 deletions(-)

Comments

Pablo Neira Ayuso Nov. 13, 2018, 8:56 a.m. UTC | #1 
On Mon, Nov 12, 2018 at 10:43:45PM +0100, Florian Westphal wrote:
> nft_compat ops do not have static storage duration, unlike all other
> expressions.
> 
> When nf_tables_expr_destroy() returns, expr->ops might have been
> free'd already, so we need to store next address before calling
> expression destructor.
> 
> For same reason, we can't deref match pointer after nft_xt_put().
> 
> This can be easily reproduced by adding msleep() before
> nft_match_destroy() returns.

Applied, thanks Florian.
diff mbox series

Patch

diff --git a/net/netfilter/nf_tables_api.c b/net/netfilter/nf_tables_api.c
index 42487d01a3ed..336187f86dbf 100644
--- a/net/netfilter/nf_tables_api.c
+++ b/net/netfilter/nf_tables_api.c
@@ -2457,7 +2457,7 @@  static int nf_tables_getrule(struct net *net, struct sock *nlsk,
 static void nf_tables_rule_destroy(const struct nft_ctx *ctx,
 				   struct nft_rule *rule)
 {
-	struct nft_expr *expr;
+	struct nft_expr *expr, *next;
 
 	/*
 	 * Careful: some expressions might not be initialized in case this
@@ -2465,8 +2465,9 @@  static void nf_tables_rule_destroy(const struct nft_ctx *ctx,
 	 */
 	expr = nft_expr_first(rule);
 	while (expr != nft_expr_last(rule) && expr->ops) {
+		next = nft_expr_next(expr);
 		nf_tables_expr_destroy(ctx, expr);
-		expr = nft_expr_next(expr);
+		expr = next;
 	}
 	kfree(rule);
 }
diff --git a/net/netfilter/nft_compat.c b/net/netfilter/nft_compat.c
index 9d0ede474224..7334e0b80a5e 100644
--- a/net/netfilter/nft_compat.c
+++ b/net/netfilter/nft_compat.c
@@ -520,6 +520,7 @@  __nft_match_destroy(const struct nft_ctx *ctx, const struct nft_expr *expr,
 		    void *info)
 {
 	struct xt_match *match = expr->ops->data;
+	struct module *me = match->me;
 	struct xt_mtdtor_param par;
 
 	par.net = ctx->net;
@@ -530,7 +531,7 @@  __nft_match_destroy(const struct nft_ctx *ctx, const struct nft_expr *expr,
 		par.match->destroy(&par);
 
 	if (nft_xt_put(container_of(expr->ops, struct nft_xt, ops)))
-		module_put(match->me);
+		module_put(me);
 }
 
 static void