From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=100.103.45.18 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1793784536; b=M5VPhq+uyJ5nGVG8moXftxaTQiI/7ZlT9SXa2SikOW547zQE4+fQ6T4h6Fsszd62yqTE Wk7ALy+J7tuuHJrRHPqlgM4rEue1vjYXWEFU7F8CwHar93g9p15Hc7Y7GuOJa21MZnXTt iLCGRcaFeVRZuzaWC9xQNOJtC4dsJZ98Ap+le0KRKPF/nTc2DOec5G9QCb48RfMWhGiCv xBEEh1sQaNZvnNXwKZXb9G9dHYOCbCcE53P4Y1Dxne5FHIE5XqMaB2F62Nc10hoMdv3WW oyiAzWAgpvYwP6LTKuRzGKViECriqe4sTz8IkbjVEI1kLWqil2IOt+Ir6NYMqV+oUTw== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1793784536; h=Received:DKIM-Signature:From:To:Cc:Subject:Date:Message-ID:X-Mailer: MIME-Version:Content-Transfer-Encoding; bh=XomczbqO81jksJLTiYfHxljFLLWvatmb0xlxuK0Ew7w=; b=K5B/u4U3LV26C0QDBS9P8Pdo1LgwtZkm6EwiCw3kPd3KN5ROacXemdV/OuN0UGn5u57X xOem8LmrwUj2OZ/n55sIilcg4pixj+YhpE6AjHQbLKPmVlNTEsAHLj03s/V1UoEb8AaEn QlU2KIoXUzzwG7KAFQHElzJwPyT5SCjBdCULErUyDVzIFAPZLlf6uflvf3y4aiRh9ihQU Ktpuom/Xu2Wk9Cy7zOpHAB8umBS7TIX+9reaVODhhH+qXveE6c9C3yBu8mMbiY7uAK4Ro Kn/j/2dr5epmDX/PdAGnjGZKFOTrn9SfII/avzRpc6Cl22Bl7RSrxIw90nm7n24YGog== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=iLfMpCQa; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id E5AD1606A331 for ; Wed, 4 Nov 2026 09:28:55 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key, unprotected) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=iLfMpCQa Received: by smtp.kernel.org (Postfix) with ESMTPSA id D1C501F0093A; Wed, 4 Nov 2026 09:28:53 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1793784535; bh=XomczbqO81jksJLTiYfHxljFLLWvatmb0xlxuK0Ew7w=; h=From:To:Cc:Subject:Date; b=iLfMpCQaC5ijo7rZpH/q5m4DdJwurSWbepYDna/1js+8MdWMflqsyncCBdustGaR0 r2DYdpbZip58VShrbVnvXhr99UbYtAywbDOl52vl2q5EnGYaaGeL9D338adf+weQjX Vb8IeS3pDi4196sb6MdIng/k/pAaFkrHL8denFvXUjiRLMa4dycTkug4xfQn/HLVYE 8wh1FmoBFqs82Uq4LJG//arkiIJKcjE0gbofEBBdV2oJX0mADxN4nsKCNDHKgJNTPV VfPJUQ+eJBwZlDk/f1kCQXlvZaqhfTgbIGV/im6WLJ2PC52ujMy9bbaxAHlT41M/8l pR+Gw7YDv04SQ== From: Eric Dumazet To: "David S . Miller" , Jakub Kicinski , Paolo Abeni Cc: Simon Horman , netdev@vger.kernel.org, edumazet@kernel.org, Jay Vosburgh , Andrew Lunn , Yun Lu Subject: [PATCH net] bonding: fix slave_cnt leak on XDP enslave failure Date: Wed, 4 Nov 2026 10:28:51 +0100 Message-ID: <20261104092851.688361-1-edumazet@kernel.org> X-Mailer: git-send-email 2.53.0 X-Mailing-List: netdev@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit bond_enslave() increments bond->slave_cnt before setting up XDP on the new slave. If that setup fails (slave has no XDP support, already has an XDP program, or dev_xdp_propagate() fails), the error path jumps to err_sysfs_del, which never decrements slave_cnt. Each failed enslave therefore leaves slave_cnt one too high: - SIOCBONDINFOQUERY reports a wrong num_slaves, - balance-rr picks slave ids beyond the end of the slave list, so bond_get_slave_by_id() falls back to the first usable slave and transmit is skewed toward it. Reproducer: ip link add bond0 type bond mode balance-rr ip link set bond0 xdpdrv obj xdp_dummy.bpf.o sec xdp for i in 0 1 2; do ip link add d$i type dummy ip link set d$i master bond0 # fails: Slave does not support XDP done num_slaves read via SIOCBONDINFOQUERY is 3 before this patch, 0 after. Add an err_dec_slave_cnt label ahead of err_sysfs_del and use it from the three XDP failure paths, which are the only failures after the increment. Fixes: 9e2ee5c7e7c3 ("net, bonding: Add XDP support to the bonding driver") Signed-off-by: Eric Dumazet --- Cc: Jay Vosburgh Cc: Andrew Lunn Cc: Yun Lu --- Discovered while reviewing https://lore.kernel.org/netdev/20261104064409.281303-1-luyun_611@163.com/ drivers/net/bonding/bond_main.c | 9 ++++++--- 1 file changed, 6 insertions(+), 3 deletions(-) diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c index 7019e5d8fdc8..7a394d0eb186 100644 --- a/drivers/net/bonding/bond_main.c +++ b/drivers/net/bonding/bond_main.c @@ -2305,7 +2305,7 @@ int bond_enslave(struct net_device *bond_dev, struct net_device *slave_dev, SLAVE_NL_ERR(bond_dev, slave_dev, extack, "Slave does not support XDP"); res = -EOPNOTSUPP; - goto err_sysfs_del; + goto err_dec_slave_cnt; } } else if (bond->xdp_prog) { struct netdev_bpf xdp = { @@ -2319,14 +2319,14 @@ int bond_enslave(struct net_device *bond_dev, struct net_device *slave_dev, SLAVE_NL_ERR(bond_dev, slave_dev, extack, "Slave has XDP program loaded, please unload before enslaving"); res = -EOPNOTSUPP; - goto err_sysfs_del; + goto err_dec_slave_cnt; } res = dev_xdp_propagate(slave_dev, &xdp); if (res < 0) { /* ndo_bpf() sets extack error message */ slave_dbg(bond_dev, slave_dev, "Error %d calling ndo_bpf\n", res); - goto err_sysfs_del; + goto err_dec_slave_cnt; } if (bond->xdp_prog) bpf_prog_inc(bond->xdp_prog); @@ -2348,6 +2348,9 @@ int bond_enslave(struct net_device *bond_dev, struct net_device *slave_dev, return 0; /* Undo stages on error */ +err_dec_slave_cnt: + WRITE_ONCE(bond->slave_cnt, bond->slave_cnt - 1); + err_sysfs_del: bond_sysfs_slave_del(new_slave); -- 2.53.0