From patchwork Tue Sep 19 08:12:47 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Johannes Nixdorf X-Patchwork-Id: 13391293 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 7EE98CD5BA0 for ; Tue, 19 Sep 2023 12:17:37 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232100AbjISMRk (ORCPT ); Tue, 19 Sep 2023 08:17:40 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:60092 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231945AbjISMR1 (ORCPT ); Tue, 19 Sep 2023 08:17:27 -0400 Received: from mail.avm.de (mail.avm.de [212.42.244.94]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 82EE8CF4; Tue, 19 Sep 2023 05:16:36 -0700 (PDT) Received: from mail-auth.avm.de (unknown [IPv6:2001:bf0:244:244::71]) by mail.avm.de (Postfix) with ESMTPS; Tue, 19 Sep 2023 14:16:34 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=avm.de; s=mail; t=1695125794; bh=4wWW7PThUEy/0/1cw0DJ8Iedw0+ZXiRRLL2Wplmz8kc=; h=From:Subject:Date:To:Cc:From; b=uEhbfVov5qB6MXdjIKtZtKFpmnMg1/rdute8l4fk71bL3KL4RbIXnDIZt8spHkEfG umwHve3uQsXC0rpCqSeW9xze62WmBD/s0r9SCv4zpLdD3xCa44K96+x3dgyMpp9wUU Va1IzP4l3S4XIIyYguYk8CRZW4ogABtwbYDGJomI= Received: from localhost (unknown [172.17.88.63]) by mail-auth.avm.de (Postfix) with ESMTPSA id E1ED582000; Tue, 19 Sep 2023 14:16:33 +0200 (CEST) From: Johannes Nixdorf Subject: [PATCH net-next v4 0/6] bridge: Add a limit on learned FDB entries Date: Tue, 19 Sep 2023 10:12:47 +0200 Message-Id: <20230919-fdb_limit-v4-0-39f0293807b8@avm.de> MIME-Version: 1.0 X-B4-Tracking: v=1; b=H4sIAP9XCWUC/02NywrCMBBFf6XM2khsG/tY+R9SJI+JHbCpJCFUS v7dUFy4PJzLuTsE9IQBxmoHj4kCra5Ae6pAz9I9kZEpDDWvGz7wllmjHi9aKDIrUShlL1fd91D 2b4+WtqN1B4eROdwiTMXMFOLqP8dJag7/64m/XmoYZ50YOm0E57KvbzItZ4Mw5Zy/5r9a/qkAA AA= To: "David S. Miller" , Andrew Lunn , David Ahern , Eric Dumazet , Florian Fainelli , Ido Schimmel , Jakub Kicinski , Nikolay Aleksandrov , Oleksij Rempel , Paolo Abeni , Roopa Prabhu , Shuah Khan , Vladimir Oltean Cc: bridge@lists.linux-foundation.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org, Johannes Nixdorf X-Mailer: b4 0.12.3 X-Developer-Signature: v=1; a=ed25519-sha256; t=1695111167; l=4268; i=jnixdorf-oss@avm.de; s=20230906; h=from:subject:message-id; bh=JapsvU38KZCfbiZTIg1IrJQMTOijSxqXyV04LE6TqvE=; b=LSlEhsCt1N4SZEhIdcd9TP66IqZACgNTfLJM+wis+YTtb90REsOeW17n3OtoFXL/TTuAWyNpq zE/Z7+CT/jwCI1wQVO3cel7EtNciNaIOqaNjLxKSKFU11wlAT7BKy0y X-Developer-Key: i=jnixdorf-oss@avm.de; a=ed25519; pk=KMraV4q7ANHRrwjf9EVhvU346JsqGGNSbPKeNILOQfo= X-purgate-ID: 149429::1695125794-C6E28D5A-CDE09CF7/0/0 X-purgate-type: clean X-purgate-size: 4308 X-purgate-Ad: Categorized by eleven eXpurgate (R) http://www.eleven.de X-purgate: This mail is considered clean (visit http://www.eleven.de for further information) X-purgate: clean Precedence: bulk List-ID: X-Mailing-List: linux-kselftest@vger.kernel.org Introduce a limit on the amount of learned FDB entries on a bridge, configured by netlink with a build time default on bridge creation in the kernel config. For backwards compatibility the kernel config default is disabling the limit (0). Without any limit a malicious actor may OOM a kernel by spamming packets with changing MAC addresses on their bridge port, so allow the bridge creator to limit the number of entries. Currently the manual entries are identified by the bridge flags BR_FDB_LOCAL or BR_FDB_ADDED_BY_USER, atomically bundled under the new flag BR_FDB_DYNAMIC_LEARNED. This means the limit also applies to entries created with BR_FDB_ADDED_BY_EXT_LEARN but none of BR_FDB_LOCAL or BR_FDB_ADDED_BY_USER, e.g. ones added by SWITCHDEV_FDB_ADD_TO_BRIDGE. Link to the corresponding iproute2 changes: https://lore.kernel.org/netdev/20230919-fdb_limit-v4-1-b4d2dc4df30f@avm.de/ Signed-off-by: Johannes Nixdorf --- Changes in v4: - Added the new test to the Makefile. (from review) - Removed _entries from the names. (from iproute2 review, in some places only for consistency) - Wrapped the lines at 80 chars, except when longer lines are consistent with neighbouring code. (from review) - Fixed a race in fdb_delete. (from review) - Link to v3: https://lore.kernel.org/r/20230905-fdb_limit-v3-0-7597cd500a82@avm.de Changes in v3: - Fixed the flags for fdb_create in fdb_add_entry to use BIT(...). Previously we passed garbage. (from review) - Set strict_start_type for br_policy. (from review) - Split out the combined accounting and limit patch, and the netlink patch from the combined patch in v2. (from review) - Count atomically, remove the newly introduced lock. (from review) - Added the new attributes to br_policy. (from review) - Added a selftest for the new feature. (from review) - Link to v2: https://lore.kernel.org/netdev/20230619071444.14625-1-jnixdorf-oss@avm.de/ Changes in v2: - Added BR_FDB_ADDED_BY_USER earlier in fdb_add_entry to ensure the limit is not applied. - Do not initialize fdb_*_entries to 0. (from review) - Do not skip decrementing on 0. (from review) - Moved the counters to a conditional hole in struct net_bridge to avoid growing the struct. (from review, it still grows the struct as there are 2 32-bit values) - Add IFLA_BR_FDB_CUR_LEARNED_ENTRIES (from review) - Fix br_get_size() with the added attributes. - Only limit learned entries, rename to *_(CUR|MAX)_LEARNED_ENTRIES. (from review) - Added a default limit in Kconfig. (deemed acceptable in review comments, helps with embedded use-cases where a special purpose kernel is built anyways) - Added an iproute2 patch for easier testing. - Link to v1: https://lore.kernel.org/netdev/20230515085046.4457-1-jnixdorf-oss@avm.de/ Obsolete v1 review comments: - Return better errors to users: Due to limiting the limit to automatically created entries, netlink fdb add requests and changing bridge ports are never rejected, so they do not yet need a more friendly error returned. --- Johannes Nixdorf (6): net: bridge: Set BR_FDB_ADDED_BY_USER early in fdb_add_entry net: bridge: Set strict_start_type for br_policy net: bridge: Track and limit dynamically learned FDB entries net: bridge: Add netlink knobs for number / max learned FDB entries net: bridge: Add a configurable default FDB learning limit selftests: forwarding: bridge_fdb_learning_limit: Add a new selftest include/uapi/linux/if_link.h | 2 + net/bridge/Kconfig | 13 + net/bridge/br_device.c | 2 + net/bridge/br_fdb.c | 42 ++- net/bridge/br_netlink.c | 17 +- net/bridge/br_private.h | 4 + tools/testing/selftests/net/forwarding/Makefile | 3 +- .../net/forwarding/bridge_fdb_learning_limit.sh | 283 +++++++++++++++++++++ 8 files changed, 359 insertions(+), 7 deletions(-) --- base-commit: ce9ecca0238b140b88f43859b211c9fdfd8e5b70 change-id: 20230904-fdb_limit-fae5bbf16c88 Best regards,