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 3904D17A2FC; Wed, 20 May 2026 18:32:31 +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=1779301952; cv=none; b=dmg7duRYwEtpH9gxQl3fDE98scxrWDIVgX6rqW7FP56DNllFLPr/jwfPB/cR/wKGXq8snBym2BCGYqWqwD9g0xMTgoF6eKPWNWstDwkkuNlL5YyC1heyq/qC2c0KeZIccjTozktY5YbCu4QydGHHNSN2R0kdBd28JOqYwleohAA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1779301952; c=relaxed/simple; bh=jVlvgMqMZu4Nl3mCrgrXVgV0kBdQzeabY0/B8Qeihrk=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=j4/lpiiefY5L+sKCCl+9vb5PBv9yh15Yh8BqZND60oZOY0XxA8smbt76rzLCzWF7ahozt7RwnF0LmfB+aOAeCmmY+ozAdN9fYtzQ8o9jzLq8nsy8mtEgpjonvZTV6gWmKT/rBUBrk/2rUPPocCfn349Z/VALRJItOEbWgkwENjk= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=zq/dmYU6; 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="zq/dmYU6" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 9DFED1F000E9; Wed, 20 May 2026 18:32:30 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1779301951; bh=3sEdDdUp+fHU4yL3t0MmHsY5bXZWLcy2VllCE1NyLrE=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=zq/dmYU6PG0CWvG/xWWUYi+wkahujM0m1mUEb/rmISxtFlPqRM444LK2l9m5rumpZ 3l2upo4Z0PCKNuEj+khxjxk5lDAPPxrzqbtaKBhTHxMMWQLEE45rgToiej17wxsR8o xMSYrZjJYe6DZWqOq1vnSY7suURJmGas1WQZKCW4= 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 6.6 040/508] bpf: Use RCU-safe iteration in dev_map_redirect_multi() SKB path Date: Wed, 20 May 2026 18:17:43 +0200 Message-ID: <20260520162059.461910515@linuxfoundation.org> X-Mailer: git-send-email 2.54.0 In-Reply-To: <20260520162058.573354582@linuxfoundation.org> References: <20260520162058.573354582@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 6.6-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 3939221bd6098..c169f0624e100 100644 --- a/kernel/bpf/devmap.c +++ b/kernel/bpf/devmap.c @@ -642,7 +642,7 @@ 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; @@ -724,7 +724,6 @@ 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; @@ -764,7 +763,7 @@ 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