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 777AC59B56 for ; Tue, 1 Sep 2026 11:11:10 +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=1788261071; cv=none; b=oGGeGId4iSaVpmxacjP7VS9cwSJ6tg0WKPUta6bRL4CM22W4VvwrzzqZln/NH4tQMmI5J9O89a9nw+eogVqqEEJg7OEZjUBbYCO5hnBH3jo/T48yDrwp3WAPdNEKxlupT9ILdWfunqFX5RXZ/o2zH3LP3UTzlO0vnNjgYUUtnu8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788261071; c=relaxed/simple; bh=xEgpyXxTrMAnNltKTjN0PWi5hE+yUx3Jd+kRXvixhc8=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=FBWHNPwHQ+tGr7JrmEYLKfKGSQkGPSWMdZyxPehKQVEEmRzMoJsnBP99/gWzzXHDzhi3Nvw3SMbrINmUSgf9xHBwUTdXW9uXLctZPpdaYdi4zJV5awJO07AeP40ViG+mn4BZ2MvTRzTt4TH34iatDG+1g4IcvCu7UDpwkQf5YrE= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=IG7GnhQX; 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="IG7GnhQX" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 5B1EA1F000E9; Tue, 1 Sep 2026 11:11:09 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1788261070; bh=lkVwTzwte5WSblH/qYuRXxaVon6lQLoUk6YcrtRAlgY=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=IG7GnhQX3fBf04+1iaPCvaiZEVQBONyaNqfKatKIPsS46qCIqF3LdwauqPAQiEuEn z7mFMQpeYT26oLOOeJmytHu9M1OptR8BrKfPAMEUdipO6MCoIOCoqFDgzy198LqVHG v5Ov1cVH4V7+DmozDp12ZTGBluEpTQxSOZuHf0x6Mmlb9H4fpWrYF1BdrzLHMs9W/+ BGQ+EmKJ4hodbExwqCli4rMJeFQiZVScqlD00MmFMHG+5VRDZuRcJMyx0Y6dxyTbbp RVtwr9s1PIy11EqVVXN83wikHRrsvWiAyGq14jWTTrs/aSvCZqM8r+PXnthp9I4yOW pnOjtPLWSzoCA== From: Sasha Levin To: stable@vger.kernel.org Cc: Kyle Zeng , Eric Dumazet , Willem de Bruijn , Willem de Bruijn , Jakub Kicinski , Sasha Levin Subject: [PATCH 6.18.y] net/packet: defer vmalloc TX_RING free until skbs finish Date: Tue, 1 Sep 2026 07:11:07 -0400 Message-ID: <20260901111107.4175171-1-sashal@kernel.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <2026083139-encroach-exemplary-64b2@gregkh> References: <2026083139-encroach-exemplary-64b2@gregkh> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Kyle Zeng [ Upstream commit 992cc9f94ca924089a506ba9b327caa9af797529 ] AF_PACKET TX_RING skbs keep a raw pointer to their ring frame. The skb page references preserve page-backed ring blocks after pg_vec is freed, but they do not preserve a vmalloc mapping. tpacket_destruct_skb() currently drops the pending reference before writing the timestamp and TP_STATUS_AVAILABLE to the frame. Move the decrement after those stores. The smp_wmb() in __packet_set_status() orders the frame stores before the decrement. Also recheck pending TX frames under pg_vec_lock before non-closing ring replacement, so a racing send cannot add a pending skb between the initial check and the ring swap. Ring allocation can produce a mixture of page-backed and vmalloc-backed blocks. Allocate deferred-work storage during TX ring setup when the first vmalloc-backed block is encountered, and keep its pointer in the pg_vec allocation header. If allocation fails, return -ENOMEM from ring setup. On socket close, a non-NULL pointer identifies a vmalloc-backed vector without a scan. If TX skbs remain, defer the whole vector to system_long_wq. After pg_vec is detached, a late destructor can skip the pending decrement. Use socket write-memory accounting as the deferred lifetime gate instead: an skb remains charged through its final sock_wfree(), after all ring-frame accesses. The delayed work retains a socket reference and reschedules itself until no TX skbs remain. Move pending_refcnt release to packet_sock_destruct() so late skb destructors and deferred cleanup can safely use it after packet_release(). Page-backed teardown remains synchronous, and no lock is added to the TX completion hot path. Fixes: b013840810c2 ("packet: use percpu mmap tx frame pending refcount") Cc: stable@vger.kernel.org Link: https://lore.kernel.org/netdev/20260721015824.45829-1-kylebot@openai.com/ Suggested-by: Eric Dumazet Suggested-by: Willem de Bruijn Reviewed-by: Willem de Bruijn Signed-off-by: Kyle Zeng Link: https://patch.msgid.link/20260816235646.76500-1-kylebot@openai.com Signed-off-by: Jakub Kicinski [ adapted the kzalloc_objs() allocation context to the older kcalloc() form ] Signed-off-by: Sasha Levin --- net/packet/af_packet.c | 96 ++++++++++++++++++++++++++++++++++++++---- 1 file changed, 87 insertions(+), 9 deletions(-) diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c index 99212023b119c..cb3376f04dfa8 100644 --- a/net/packet/af_packet.c +++ b/net/packet/af_packet.c @@ -87,6 +87,7 @@ #include #include #include +#include #ifdef CONFIG_INET #include #endif @@ -1339,6 +1340,8 @@ static void packet_sock_destruct(struct sock *sk) WARN_ON(atomic_read(&sk->sk_rmem_alloc)); WARN_ON(refcount_read(&sk->sk_wmem_alloc)); + packet_free_pending(pkt_sk(sk)); + if (!sock_flag(sk, SOCK_DEAD)) { pr_err("Attempt to release alive packet socket: %p\n", sk); return; @@ -2533,11 +2536,11 @@ static void tpacket_destruct_skb(struct sk_buff *skb) __u32 ts; ph = skb_zcopy_get_nouarg(skb); - packet_dec_pending(&po->tx_ring); ts = __packet_set_timestamp(po, ph, skb); __packet_set_status(po, ph, TP_STATUS_AVAILABLE | ts); + packet_dec_pending(&po->tx_ring); complete(&po->skb_completion); } @@ -3206,7 +3209,6 @@ static int packet_release(struct socket *sock) /* Purge queues */ skb_queue_purge(&sk->sk_receive_queue); - packet_free_pending(po); sock_put(sk); return 0; @@ -4370,11 +4372,26 @@ static const struct vm_operations_struct packet_mmap_ops = { .close = packet_mm_close, }; +struct packet_pg_vec { + struct packet_pg_vec_free *deferred; + unsigned int order; + unsigned int len; + struct pgv pg_vec[] __counted_by(len); +}; + +struct packet_pg_vec_free { + struct delayed_work work; + struct sock *sk; + struct packet_pg_vec *vec; +}; + static void free_pg_vec(struct pgv *pg_vec, unsigned int order, unsigned int len) { + struct packet_pg_vec *vec; int i; + vec = container_of_const(pg_vec, struct packet_pg_vec, pg_vec[0]); for (i = 0; i < len; i++) { if (likely(pg_vec[i].buffer)) { if (is_vmalloc_addr(pg_vec[i].buffer)) @@ -4385,7 +4402,46 @@ static void free_pg_vec(struct pgv *pg_vec, unsigned int order, pg_vec[i].buffer = NULL; } } - kfree(pg_vec); + kfree(vec->deferred); + kfree(vec); +} + +static void packet_free_pg_vec_work(struct work_struct *work) +{ + struct packet_pg_vec_free *deferred; + struct packet_pg_vec *vec; + struct sock *sk; + + deferred = container_of_const(to_delayed_work(work), + struct packet_pg_vec_free, work); + vec = deferred->vec; + sk = deferred->sk; + if (sk_wmem_alloc_get(sk)) { + queue_delayed_work(system_long_wq, &deferred->work, 1); + return; + } + + free_pg_vec(vec->pg_vec, vec->order, vec->len); + sock_put(sk); +} + +static void packet_free_tx_ring(struct sock *sk, struct pgv *pg_vec, + unsigned int order, unsigned int len) +{ + struct packet_pg_vec_free *deferred; + struct packet_pg_vec *vec; + + vec = container_of_const(pg_vec, struct packet_pg_vec, pg_vec[0]); + deferred = vec->deferred; + if (!deferred || !sk_wmem_alloc_get(sk)) { + free_pg_vec(pg_vec, order, len); + return; + } + + /* A detached ring's pending count can miss late skb destructors. */ + deferred->sk = sk; + sock_hold(sk); + queue_delayed_work(system_long_wq, &deferred->work, 0); } static char *alloc_one_pg_vec_page(unsigned long order) @@ -4413,20 +4469,35 @@ static char *alloc_one_pg_vec_page(unsigned long order) return NULL; } -static struct pgv *alloc_pg_vec(struct tpacket_req *req, int order) +static struct pgv *alloc_pg_vec(struct tpacket_req *req, int order, bool tx_ring) { unsigned int block_nr = req->tp_block_nr; + struct packet_pg_vec *vec; struct pgv *pg_vec; int i; - pg_vec = kcalloc(block_nr, sizeof(struct pgv), GFP_KERNEL | __GFP_NOWARN); - if (unlikely(!pg_vec)) - goto out; + vec = kzalloc_flex(*vec, pg_vec, block_nr, GFP_KERNEL | __GFP_NOWARN); + if (unlikely(!vec)) + return NULL; + vec->order = order; + vec->len = block_nr; + pg_vec = vec->pg_vec; for (i = 0; i < block_nr; i++) { pg_vec[i].buffer = alloc_one_pg_vec_page(order); if (unlikely(!pg_vec[i].buffer)) goto out_free_pgvec; + + if (tx_ring && !vec->deferred && + is_vmalloc_addr(pg_vec[i].buffer)) { + vec->deferred = kzalloc_obj(*vec->deferred, + GFP_KERNEL | __GFP_NOWARN); + if (!vec->deferred) + goto out_free_pgvec; + vec->deferred->vec = vec; + INIT_DELAYED_WORK(&vec->deferred->work, + packet_free_pg_vec_work); + } } out: @@ -4509,7 +4580,7 @@ static int packet_set_ring(struct sock *sk, union tpacket_req_u *req_u, err = -ENOMEM; order = get_order(req->tp_block_size); - pg_vec = alloc_pg_vec(req, order); + pg_vec = alloc_pg_vec(req, order, tx_ring); if (unlikely(!pg_vec)) goto out; switch (po->tp_version) { @@ -4561,6 +4632,9 @@ static int packet_set_ring(struct sock *sk, union tpacket_req_u *req_u, err = -EBUSY; mutex_lock(&po->pg_vec_lock); if (closing || atomic_long_read(&po->mapped) == 0) { + if (tx_ring && !closing && packet_read_pending(rb)) + goto out_unlock; + err = 0; spin_lock_bh(&rb_queue->lock); swap(rb->pg_vec, pg_vec); @@ -4582,6 +4656,7 @@ static int packet_set_ring(struct sock *sk, union tpacket_req_u *req_u, pr_err("packet_mmap: vma is busy: %ld\n", atomic_long_read(&po->mapped)); } +out_unlock: mutex_unlock(&po->pg_vec_lock); spin_lock(&po->bind_lock); @@ -4603,7 +4678,10 @@ static int packet_set_ring(struct sock *sk, union tpacket_req_u *req_u, out_free_pg_vec: if (pg_vec) { bitmap_free(rx_owner_map); - free_pg_vec(pg_vec, order, req->tp_block_nr); + if (tx_ring && closing) + packet_free_tx_ring(sk, pg_vec, order, req->tp_block_nr); + else + free_pg_vec(pg_vec, order, req->tp_block_nr); } out: return err; -- 2.53.0