From db99f122cbf890dccc59030ea5cfb4d71f7d47f6 Mon Sep 17 00:00:00 2001 From: Florian Westphal Date: Mon, 14 Jan 2019 14:28:48 +0100 Subject: [PATCH] netfilter: nft_compat: use refcnt_t type for nft_xt reference count [ Upstream commit 12c44aba6618b7f6c437076e5722237190f6cd5f ] Using standard integer type was fine while all operations on it were guarded by the nftnl subsys mutex. This isn't true anymore: 1. transactions are guarded only by a pernet mutex, so concurrent rule manipulation in different netns is racy 2. the ->destroy hook runs from a work queue after the transaction mutex has been released already. cpu0 cpu1 (net 1) cpu2 (net 2) kworker nft_compat->destroy nft_compat->init nft_compat->init if (--nft_xt->ref == 0) nft_xt->ref++ nft_xt->ref++ Switch to refcount_t. Doing this however only fixes a minor aspect, nft_compat also performs linked-list operations in an unsafe way. This is addressed in the next two patches. Fixes: f102d66b335a ("netfilter: nf_tables: use dedicated mutex to guard transactions") Fixes: 0935d5588400 ("netfilter: nf_tables: asynchronous release") Reported-by: Taehee Yoo Signed-off-by: Florian Westphal Signed-off-by: Pablo Neira Ayuso Signed-off-by: Sasha Levin --- net/netfilter/nft_compat.c | 16 ++++++++-------- 1 file changed, 8 insertions(+), 8 deletions(-) diff --git a/net/netfilter/nft_compat.c b/net/netfilter/nft_compat.c index 38da1f5..24ec955 100644 --- a/net/netfilter/nft_compat.c +++ b/net/netfilter/nft_compat.c @@ -26,7 +26,7 @@ struct nft_xt { struct list_head head; struct nft_expr_ops ops; - unsigned int refcnt; + refcount_t refcnt; /* Unlike other expressions, ops doesn't have static storage duration. * nft core assumes they do. We use kfree_rcu so that nft core can @@ -45,7 +45,7 @@ struct nft_xt_match_priv { static bool nft_xt_put(struct nft_xt *xt) { - if (--xt->refcnt == 0) { + if (refcount_dec_and_test(&xt->refcnt)) { list_del(&xt->head); kfree_rcu(xt, rcu_head); return true; @@ -273,7 +273,7 @@ nft_target_init(const struct nft_ctx *ctx, const struct nft_expr *expr, return -EINVAL; nft_xt = container_of(expr->ops, struct nft_xt, ops); - nft_xt->refcnt++; + refcount_inc(&nft_xt->refcnt); return 0; } @@ -468,7 +468,7 @@ __nft_match_init(const struct nft_ctx *ctx, const struct nft_expr *expr, return ret; nft_xt = container_of(expr->ops, struct nft_xt, ops); - nft_xt->refcnt++; + refcount_inc(&nft_xt->refcnt); return 0; } @@ -770,7 +770,7 @@ nft_match_select_ops(const struct nft_ctx *ctx, goto err; } - nft_match->refcnt = 0; + refcount_set(&nft_match->refcnt, 0); nft_match->ops.type = &nft_match_type; nft_match->ops.eval = nft_match_eval; nft_match->ops.init = nft_match_init; @@ -874,7 +874,7 @@ nft_target_select_ops(const struct nft_ctx *ctx, goto err; } - nft_target->refcnt = 0; + refcount_set(&nft_target->refcnt, 0); nft_target->ops.type = &nft_target_type; nft_target->ops.size = NFT_EXPR_SIZE(XT_ALIGN(target->targetsize)); nft_target->ops.init = nft_target_init; @@ -945,7 +945,7 @@ static void __exit nft_compat_module_exit(void) list_for_each_entry_safe(xt, next, &nft_target_list, head) { struct xt_target *target = xt->ops.data; - if (WARN_ON_ONCE(xt->refcnt)) + if (WARN_ON_ONCE(refcount_read(&xt->refcnt))) continue; module_put(target->me); kfree(xt); @@ -954,7 +954,7 @@ static void __exit nft_compat_module_exit(void) list_for_each_entry_safe(xt, next, &nft_match_list, head) { struct xt_match *match = xt->ops.data; - if (WARN_ON_ONCE(xt->refcnt)) + if (WARN_ON_ONCE(refcount_read(&xt->refcnt))) continue; module_put(match->me); kfree(xt); -- 2.7.4