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 F404135AC18; Wed, 20 May 2026 17:20:42 +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=1779297644; cv=none; b=PG5zOrUY5/8TwML/GqLdkHuJrmgfEVwxho4Hwm6CLUGTImp2YHEjuRtqYh1h1JBS94IOclEuywLPngRCu0cuGtCnskTm/RuEyDiGOFy1ccvT9FocjkV7k89GYwBEQBQ8jRlHJD3EKgcGWeymZJW8AZ53ID4eLF26P6i0gQQiczM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1779297644; c=relaxed/simple; bh=ygqdcyfh6+CsYY5rRaRBsgqFAm6uA+wbczBkFVhr+vw=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=CykZM4KN3ueHobT7H6T5qBAJy+j7t4QattsU0DO5sPgWajuSeDEOqWg9hY0zY4DmzLaOnWYjZeCTeFAeyrIWLbysswsQYe7/geQG5OwYZMQ/62wR36/H48mgzVI24eifLmO3+DVZkeXIJbuyXMQksbVdG9nABaRBZur0w81JHi4= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=zv7UIQz1; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="zv7UIQz1" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 664571F000E9; Wed, 20 May 2026 17:20:42 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1779297642; bh=koLatfhmtlfhvz+VeYGCKYUcd/FIeh6molGpo+9Mg4A=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=zv7UIQz1uBhfPVZkWvDBMdbUA7RkGqGcm/WriVnBE/27m13bFWWt3QQDR+VY57jRL UxfKFyFZJPM6DgwK4k31n0wW3BiMYP7x441v3ttthQzUEazpO3uaHn+BdICs5tWpVl s9/Ha3+alq/RO6FM/2Fomfqm1jYrUcvyp0FijZIg= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, David Carlier , Martin KaFai Lau , Sasha Levin Subject: [PATCH 6.18 109/957] bpf: Use RCU-safe iteration in dev_map_redirect_multi() SKB path Date: Wed, 20 May 2026 18:09:52 +0200 Message-ID: <20260520162136.924472109@linuxfoundation.org> X-Mailer: git-send-email 2.54.0 In-Reply-To: <20260520162134.554764788@linuxfoundation.org> References: <20260520162134.554764788@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.18-stable review patch. If anyone has any objections, please let me know. ------------------ From: David Carlier [ Upstream commit 8ed82f807bb09d2c8455aaa665f2c6cb17bc6a19 ] The DEVMAP_HASH branch in dev_map_redirect_multi() uses hlist_for_each_entry_safe() to iterate hash buckets, but this function runs under RCU protection (called from xdp_do_generic_redirect_map() in softirq context). Concurrent writers (__dev_map_hash_update_elem, dev_map_hash_delete_elem) modify the list using RCU primitives (hlist_add_head_rcu, hlist_del_rcu). hlist_for_each_entry_safe() performs plain pointer dereferences without rcu_dereference(), missing the acquire barrier needed to pair with writers' rcu_assign_pointer(). On weakly-ordered architectures (ARM64, POWER), a reader can observe a partially-constructed node. It also defeats CONFIG_PROVE_RCU lockdep validation and KCSAN data-race detection. Replace with hlist_for_each_entry_rcu() using rcu_read_lock_bh_held() as the lockdep condition, consistent with the rcu_dereference_check() used in the DEVMAP (non-hash) branch of the same functions. Also fix the same incorrect lockdep_is_held(&dtab->index_lock) condition in dev_map_enqueue_multi(), where the lock is not held either. Fixes: e624d4ed4aa8 ("xdp: Extend xdp_redirect_map with broadcast support") Signed-off-by: David Carlier Signed-off-by: Martin KaFai Lau Link: https://patch.msgid.link/20260320072645.16731-1-devnexen@gmail.com Signed-off-by: Sasha Levin --- kernel/bpf/devmap.c | 5 ++--- 1 file changed, 2 insertions(+), 3 deletions(-) diff --git a/kernel/bpf/devmap.c b/kernel/bpf/devmap.c index 3d619d01088e3..cc0a43ebab6b9 100644 --- a/kernel/bpf/devmap.c +++ b/kernel/bpf/devmap.c @@ -665,7 +665,7 @@ int dev_map_enqueue_multi(struct xdp_frame *xdpf, struct net_device *dev_rx, for (i = 0; i < dtab->n_buckets; i++) { head = dev_map_index_hash(dtab, i); hlist_for_each_entry_rcu(dst, head, index_hlist, - lockdep_is_held(&dtab->index_lock)) { + rcu_read_lock_bh_held()) { if (!is_valid_dst(dst, xdpf)) continue; @@ -747,7 +747,6 @@ int dev_map_redirect_multi(struct net_device *dev, struct sk_buff *skb, struct bpf_dtab_netdev *dst, *last_dst = NULL; int excluded_devices[1+MAX_NEST_DEV]; struct hlist_head *head; - struct hlist_node *next; int num_excluded = 0; unsigned int i; int err; @@ -787,7 +786,7 @@ int dev_map_redirect_multi(struct net_device *dev, struct sk_buff *skb, } else { /* BPF_MAP_TYPE_DEVMAP_HASH */ for (i = 0; i < dtab->n_buckets; i++) { head = dev_map_index_hash(dtab, i); - hlist_for_each_entry_safe(dst, next, head, index_hlist) { + hlist_for_each_entry_rcu(dst, head, index_hlist, rcu_read_lock_bh_held()) { if (is_ifindex_excluded(excluded_devices, num_excluded, dst->dev->ifindex)) continue; -- 2.53.0