From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 59830214A84 for ; Wed, 2 Sep 2026 00:33:24 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788309205; cv=none; b=ZU3bqeR6/fojTAs5GhnLFBFQTt5vU39LizrwkQC+RcgG5LWzOeAxvicF3n+XYi1GQIgQMfj/4iqATh/aX8tgY7fhAmFUIrKTQsuFb3q749anT11OmvpBoNOgrax8w1vLjqvsBb7ZfhOkC0uCSoxpcIeSQLyPgKvB/lKM4rXRc2k= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788309205; c=relaxed/simple; bh=9BAeI96GJXekyNXifNx5S04jydUznCppSpdUgwHTKno=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=Z/ZjMs5zGPb2LHAphnmcAXI5tMzRwihjHuiYV6XMIwWTHbfo7Z5GCaUC+c5ugf9DJmVOQ6tT8SVwOkiCenqtKCiKZlvfIRLF5n06sx3+ZTRRDza7yNk04YRf2m86Px3Aa67m73CAeVwUM5HHSe/iOveE2TnAlmcs0QUlbS4MJRc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=RDPdu5X3; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="RDPdu5X3" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 24F7B1F000E9; Wed, 2 Sep 2026 00:33:23 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1788309203; bh=pye7qFinXyxz9uBgglgXAPmw0t8ZvCFfn4hs9yuS5DQ=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=RDPdu5X3r2GH6cUnJzgvMXOckXXdltDz2wHJYnQ1tpXdIEekDCDfcReHZYJ1sBGCL E7oW/PltCf0jeAlgvDuDiOY9n940ZdgGOBT+KVvKVN6ZqeD03Pgla+eJnvSBt7IHhq +nrBxiRPhGxP3ZylJqQ7GIHabzxcdBp6AmZUNWO4mPJUIyqSAzzKPcGx/JyOrOL57U aaAafduNSdzE0VKLPZoGQ0nmNFwqNk3/yj9rTP2Lu+42AUBimFaIgzAci5G3/aeH8Z EVLpOYJyLaRAloW9TMyyyF/cqIlzhXydgiVirevcxiKhSdwagc0/FxOEDXJKAI6Yic Zrk6bXxCL8S4g== From: Sasha Levin To: stable@vger.kernel.org Cc: Fourie Zhang , stable@kernel.org, TencentOS Corvus AI , Fourie Zhang , Pablo Neira Ayuso , Sasha Levin Subject: [PATCH 5.15.y] netfilter: nf_tables: don't queue packet path object notifications Date: Tue, 1 Sep 2026 20:33:21 -0400 Message-ID: <20260902003321.1792151-1-sashal@kernel.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <2026083158-undecided-swear-7f28@gregkh> References: <2026083158-undecided-swear-7f28@gregkh> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit From: Fourie Zhang [ Upstream commit 7904b94768e983bcb2be34a8d6d1f3450f5b838b ] All file:line references below are against v7.2-rc4 (ac5b0e5651b1). The trace was captured on 7.2.0-rc6-kasan72rc6 (075b74841bd0), where the same lines apply. nft_obj_notify() is exported and reached from the packet path. Its only in-tree caller is nft_quota_obj_eval() (net/netfilter/nft_quota.c:68), which notifies with GFP_ATOMIC while evaluating a rule for a transiting packet, holding no mutex. Since commit 67cc570edaa0 ("netfilter: nf_tables: coalesce multiple notifications into one skbuff") that notification is no longer sent immediately. __nft_obj_notify() queues it onto nft_net->notify_list via nft_notify_enqueue() (net/netfilter/nf_tables_api.c:1211), which is a bare list_add_tail(). notify_list has no lock of its own (include/net/netfilter/nf_tables.h:1951), it is serialised by commit_mutex: the six other enqueue sites all run inside a netlink transaction, and the drain in nft_commit_notify() (net/netfilter/nf_tables_api.c:10746) does list_del() + kfree_skb() from nf_tables_commit() with commit_mutex held. Sending packets through a chain that references a depleted quota object therefore races an unlocked list_add_tail() against list_del() + kfree_skb() on another CPU. The WRITE_ONCE(prev->next, new) in __list_add() then stores through an sk_buff that has already been freed: BUG: KASAN: slab-use-after-free in __nft_obj_notify+0x2c5/0x2d0 Write of size 8 at addr ff110001047183c0 by task poc/76 CPU: 0 UID: 1000 PID: 76 Comm: poc Tainted: G W 7.2.0-rc6-kasan72rc6 #4 Call Trace: __nft_obj_notify (include/linux/list.h:164 include/linux/list.h:191 net/netfilter/nf_tables_api.c:1211 net/netfilter/nf_tables_api.c:8743) nft_quota_obj_eval (net/netfilter/nft_quota.c:68) nft_do_chain_inet nf_hook_slow __ip_local_out ip_push_pending_frames udp_send_skb udp_sendmsg __x64_sys_sendto Allocated by task 77: __alloc_skb (net/core/skbuff.c:704) __nft_obj_notify (include/net/netlink.h:1055 net/netfilter/nf_tables_api.c:8731) nft_quota_obj_eval (net/netfilter/nft_quota.c:68) nft_do_chain Freed by task 79: nf_tables_commit (include/linux/skbuff.h:1332 net/netfilter/nf_tables_api.c:10759 net/netfilter/nf_tables_api.c:11185) nfnetlink_rcv_batch (net/netfilter/nfnetlink.c:574) netlink_unicast netlink_sendmsg The buggy address belongs to the cache skbuff_head_cache of size 232 Queueing from the packet path is wrong even leaving the race aside: notify_list is only drained by nft_commit_notify() from nf_tables_commit() (:11185), so a notification enqueued outside a transaction is not sent until some later netlink batch commits, if one ever does. The gfp argument that nft_obj_notify() still takes is a leftover of the pre-67cc570edaa0 behaviour, where this path called nfnetlink_send() directly. Restore that: split the message construction out into nft_obj_notify_alloc() and let each caller decide what to do with the skb. nft_obj_notify(), the exported one reached from the packet path, sends it straight away; nf_tables_obj_notify(), which runs under commit_mutex, keeps queueing it, so transaction notifications are still coalesced. Fixes: 67cc570edaa0 ("netfilter: nf_tables: coalesce multiple notifications into one skbuff") Cc: stable@kernel.org Reported-by: TencentOS Corvus AI Assisted-by: tencentos-corvus-ai:kimi-k3 Signed-off-by: Fourie Zhang Signed-off-by: Pablo Neira Ayuso [ adapted the notification allocation helper to retain 5.15’s combined audit handling ] Signed-off-by: Sasha Levin --- net/netfilter/nf_tables_api.c | 38 +++++++++++++++++++++++++++-------- 1 file changed, 30 insertions(+), 8 deletions(-) diff --git a/net/netfilter/nf_tables_api.c b/net/netfilter/nf_tables_api.c index 021a2a34b8a12..24180b0d58886 100644 --- a/net/netfilter/nf_tables_api.c +++ b/net/netfilter/nf_tables_api.c @@ -7586,9 +7586,10 @@ static int nf_tables_delobj(struct sk_buff *skb, const struct nfnl_info *info, return nft_delobj(&ctx, obj); } -void nft_obj_notify(struct net *net, const struct nft_table *table, - struct nft_object *obj, u32 portid, u32 seq, int event, - u16 flags, int family, int report, gfp_t gfp) +static struct sk_buff * +nft_obj_notify_alloc(struct net *net, const struct nft_table *table, + struct nft_object *obj, u32 portid, u32 seq, int event, + u16 flags, int family, int report, gfp_t gfp) { struct nftables_pernet *nft_net = nft_pernet(net); struct sk_buff *skb; @@ -7607,7 +7608,7 @@ void nft_obj_notify(struct net *net, const struct nft_table *table, if (!report && !nfnetlink_has_listeners(net, NFNLGRP_NFTABLES)) - return; + return NULL; skb = nlmsg_new(NLMSG_GOODSIZE, gfp); if (skb == NULL) @@ -7621,18 +7622,39 @@ void nft_obj_notify(struct net *net, const struct nft_table *table, goto err; } - nft_notify_enqueue(skb, report, &nft_net->notify_list); - return; + return skb; err: nfnetlink_set_err(net, portid, NFNLGRP_NFTABLES, -ENOBUFS); + return NULL; +} + +void nft_obj_notify(struct net *net, const struct nft_table *table, + struct nft_object *obj, u32 portid, u32 seq, int event, + u16 flags, int family, int report, gfp_t gfp) +{ + struct sk_buff *skb; + + /* Called from the packet path, holding no mutex: notify_list is + * serialised by commit_mutex, so send this notification directly. + */ + skb = nft_obj_notify_alloc(net, table, obj, portid, seq, event, + flags, family, report, gfp); + if (skb) + nfnetlink_send(skb, net, portid, NFNLGRP_NFTABLES, report, gfp); } EXPORT_SYMBOL_GPL(nft_obj_notify); static void nf_tables_obj_notify(const struct nft_ctx *ctx, struct nft_object *obj, int event) { - nft_obj_notify(ctx->net, ctx->table, obj, ctx->portid, ctx->seq, event, - ctx->flags, ctx->family, ctx->report, GFP_KERNEL); + struct nftables_pernet *nft_net = nft_pernet(ctx->net); + struct sk_buff *skb; + + skb = nft_obj_notify_alloc(ctx->net, ctx->table, obj, ctx->portid, + ctx->seq, event, ctx->flags, ctx->family, + ctx->report, GFP_KERNEL); + if (skb) + nft_notify_enqueue(skb, ctx->report, &nft_net->notify_list); } /* -- 2.53.0