The nft_compat destroy function deletes the nft_xt object from a list. This isn't allowed anymore. Destroy functions are called asynchronously, i.e. next batch can find the object that has a pending ->destroy() invocation:
cpu0 cpu1 worker ->destroy for_each_entry() if (x == ... return x->ops; list_del(x) kfree_rcu(x) expr->ops->... // ops was free'd
To resolve this, the list_del needs to occur before the transaction mutex gets released. nf_tables has a 'deactivate' hook for this purpose, so use that to unlink the object from the list.
Fixes: 0935d5588400 ("netfilter: nf_tables: asynchronous release") Reported-by: Taehee Yoo ap420073@gmail.com Signed-off-by: Florian Westphal fw@strlen.de Signed-off-by: Pablo Neira Ayuso pablo@netfilter.org --- net/netfilter/nft_compat.c | 48 +++++++++++++++++++++++++++++++++++++- 1 file changed, 47 insertions(+), 1 deletion(-)
diff --git a/net/netfilter/nft_compat.c b/net/netfilter/nft_compat.c index 61c098555507..432139b7fa1f 100644 --- a/net/netfilter/nft_compat.c +++ b/net/netfilter/nft_compat.c @@ -29,6 +29,9 @@ struct nft_xt { struct nft_expr_ops ops; refcount_t refcnt;
+ /* used only when transaction mutex is locked */ + unsigned int listcnt; + /* Unlike other expressions, ops doesn't have static storage duration. * nft core assumes they do. We use kfree_rcu so that nft core can * can check expr->ops->size even after nft_compat->destroy() frees @@ -61,7 +64,7 @@ static struct nft_compat_net *nft_compat_pernet(struct net *net) static bool nft_xt_put(struct nft_xt *xt) { if (refcount_dec_and_test(&xt->refcnt)) { - list_del(&xt->head); + WARN_ON_ONCE(!list_empty(&xt->head)); kfree_rcu(xt, rcu_head); return true; } @@ -537,6 +540,43 @@ nft_match_destroy(const struct nft_ctx *ctx, const struct nft_expr *expr) __nft_match_destroy(ctx, expr, nft_expr_priv(expr)); }
+static void nft_compat_activate(const struct nft_ctx *ctx, + const struct nft_expr *expr, + struct list_head *h) +{ + struct nft_xt *xt = container_of(expr->ops, struct nft_xt, ops); + + if (xt->listcnt == 0) + list_add(&xt->head, h); + + xt->listcnt++; +} + +static void nft_compat_activate_mt(const struct nft_ctx *ctx, + const struct nft_expr *expr) +{ + struct nft_compat_net *cn = nft_compat_pernet(ctx->net); + + nft_compat_activate(ctx, expr, &cn->nft_match_list); +} + +static void nft_compat_activate_tg(const struct nft_ctx *ctx, + const struct nft_expr *expr) +{ + struct nft_compat_net *cn = nft_compat_pernet(ctx->net); + + nft_compat_activate(ctx, expr, &cn->nft_target_list); +} + +static void nft_compat_deactivate(const struct nft_ctx *ctx, + const struct nft_expr *expr) +{ + struct nft_xt *xt = container_of(expr->ops, struct nft_xt, ops); + + if (--xt->listcnt == 0) + list_del_init(&xt->head); +} + static void nft_match_large_destroy(const struct nft_ctx *ctx, const struct nft_expr *expr) { @@ -789,6 +829,8 @@ nft_match_select_ops(const struct nft_ctx *ctx, nft_match->ops.eval = nft_match_eval; nft_match->ops.init = nft_match_init; nft_match->ops.destroy = nft_match_destroy; + nft_match->ops.activate = nft_compat_activate_mt; + nft_match->ops.deactivate = nft_compat_deactivate; nft_match->ops.dump = nft_match_dump; nft_match->ops.validate = nft_match_validate; nft_match->ops.data = match; @@ -805,6 +847,7 @@ nft_match_select_ops(const struct nft_ctx *ctx,
nft_match->ops.size = matchsize;
+ nft_match->listcnt = 1; list_add(&nft_match->head, &cn->nft_match_list);
return &nft_match->ops; @@ -891,6 +934,8 @@ nft_target_select_ops(const struct nft_ctx *ctx, nft_target->ops.size = NFT_EXPR_SIZE(XT_ALIGN(target->targetsize)); nft_target->ops.init = nft_target_init; nft_target->ops.destroy = nft_target_destroy; + nft_target->ops.activate = nft_compat_activate_tg; + nft_target->ops.deactivate = nft_compat_deactivate; nft_target->ops.dump = nft_target_dump; nft_target->ops.validate = nft_target_validate; nft_target->ops.data = target; @@ -900,6 +945,7 @@ nft_target_select_ops(const struct nft_ctx *ctx, else nft_target->ops.eval = nft_target_eval_xt;
+ nft_target->listcnt = 1; list_add(&nft_target->head, &cn->nft_target_list);
return &nft_target->ops;