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 721F132D42B; Sat, 30 May 2026 17:07:46 +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=1780160867; cv=none; b=uIpaqtjmUZIP8We6sy5U/7aJWv7VEfJr40Io3ipBBAKTYFrvmdlNJ0axKbm3dyYP3Na05YdbX8hx8BwNXwRf7fR4Bod/e8qMkEcXLR7xXAh9UZXpECumytD903cR+q8s2GywV2w+6cUPU2MACPL+eLMtHFroyCFtylOrOerNvjc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1780160867; c=relaxed/simple; bh=m2t1hFx4T+xyp2xizDQ+3FyzOJUCa0QSIl3I161DBKo=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=srilej8bNQQmNuAZXiW1CfZWD4/I+T2Abt6Bk5HTq5/1l4P22hZT5pdLUl2xi3syROsUxV7rT4v3/5nAX5qLmxjCL8/ZsEzBvTUmatxedyD561VkGgkTIhEFjiev36Cir39UFLL1YG/tU0C223DK5paXklzDfdnN2MLbreJ1tyw= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=vN604fZI; 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="vN604fZI" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 78F961F00898; Sat, 30 May 2026 17:07:45 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1780160866; bh=eHDl/1gWkX9CdgFxpWqx1zCCaUHG1HDGdiZJOa3OctM=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=vN604fZI7ELauYizn0uhe35wEeqSfQxi6hFruyd0ol78uI4b4d9LZBF0m9MCRXGer s6+KCc0p2Wm5dD2CskadIF4MB5xyJuohZ0DW71I7CplObqPKZE7tsO/xJOKRuCiWsX YN5Wcc2iP6ZmYdXVSjZHI7z41WSE0GKOxLlrDsf0= 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 6.1 457/969] bpf: Use RCU-safe iteration in dev_map_redirect_multi() SKB path Date: Sat, 30 May 2026 17:59:41 +0200 Message-ID: <20260530160312.900762341@linuxfoundation.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260530160300.485627683@linuxfoundation.org> References: <20260530160300.485627683@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 6.1-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 71025d1311a57..c8d8977296bc1 100644 --- a/kernel/bpf/devmap.c +++ b/kernel/bpf/devmap.c @@ -636,7 +636,7 @@ 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; @@ -718,7 +718,6 @@ 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; @@ -758,7 +757,7 @@ 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