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

[ Upstream commit 29e3880109e357fdc607b4393f8308cef6af9413 ]

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>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/net/netfilter/nf_tables_api.c b/net/netfilter/nf_tables_api.c
index 3ae365f92bff5892a54ce22a9bd4f4fea316e2e7..ea1e57daf50edd1a4f5f1593c6ae0655a4c0d903 100644 (file)
--- a/net/netfilter/nf_tables_api.c
+++ b/net/netfilter/nf_tables_api.c
@@ -2252,7 +2252,7 @@ err:
 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
@@ -2260,8 +2260,9 @@ 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 6da1cec1494a9c8ff9b00c44fdf2ac3c09b4fe54..7533c2fd6b769d82c3866c5a277f800fab8bac38 100644 (file)
--- a/net/netfilter/nft_compat.c
+++ b/net/netfilter/nft_compat.c
@@ -497,6 +497,7 @@ __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;
@@ -507,7 +508,7 @@ __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