From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out-172.mta1.migadu.com (out-172.mta1.migadu.com [95.215.58.172]) (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 56C6A1870; Fri, 4 Oct 2024 01:14:20 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=95.215.58.172 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1728004463; cv=none; b=aRFf+MetZ78fody3tiaSI4AcYxf4QW2qz23gpQv5dZ3/YlpSiil93nEfXelTj3aF7rWgoeoCfEl13U3nQHTya6QImlvWYvGaWFbxKDf0qKi8y+mR4QvWaArfleOgBYnyd4xYno14ssgeFdwtPawQVEyRNfiFOjtWAemeDyUwiLU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1728004463; c=relaxed/simple; bh=m7Oas5tvrHfupQwzAwy/sYVnzVi8o8tPjsW++fKGZL0=; h=Message-ID:Date:MIME-Version:From:Subject:To:Cc:Content-Type; b=E7/DI2JpyldVY7Qx+vDyaKKixej33AgNajnBmcpYEIwHx9ETp1GqZVvwKkOZ4e21uZHZ6WgtzXRb48L/ri/ywYgufVpXMAXDWUBNnDOv4UgsujtU3xaexMJgGzUjDWdMOzevCV9pPuh9jjVNKMxSBwhHODv/HIWkz1KRpetpeeg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b=BWVnt93N; arc=none smtp.client-ip=95.215.58.172 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b="BWVnt93N" Message-ID: DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1728004458; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding; bh=X2Ow6n9yG7Zu5N96hb8gmL3PUFGycoog6CmimF35atI=; b=BWVnt93N3EPPLiO1TlE05Wy0X2IhGKF7RMvy6pif6m+Ioo6lW/EisEsNtDJWVhV6+7gR8H 1hpdM5bIAdBOpcelh6LrXjO7OiSaiPvtLaO6ZdNq/YV6ixg4zfH9PMSHFwKN3slH7P+N2l FLbNSSyEM9WMLuvLmbDFam5Y1PfCJJ8= Date: Thu, 3 Oct 2024 18:14:09 -0700 Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Martin KaFai Lau Subject: [Question]: A non NULL req->sk in tcp_rtx_synack. Not a fastopen connection. To: Network Development Cc: Eric Dumazet , Jakub Kicinski , Kuniyuki Iwashima , bpf Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Migadu-Flow: FLOW_OUT Hi, We are seeing a use-after-free from a bpf prog attached to trace_tcp_retransmit_synack. The program passes the req->sk to the bpf_sk_storage_get_tracing kernel helper which does check for null before using it. fastopen is not used. We got a kfence report on use-after-free (pasted at the end). It is running with an older 6.4 kernel and we hardly hit this in production. From the upstream code, del_timer_sync() should have been done by inet_csk_reqsk_queue_drop() before "req->sk = child;" is assigned in inet_csk_reqsk_queue_add(). My understanding is the req->rsk_timer should have been stopped before the "req->sk = child;" assignment. or there are cases that req->sk is not NULL in the reqsk_timer_handler()? BUG: KFENCE: use-after-free read in bpf_sk_storage_get_tracing+0x2e/0x1b0 Use-after-free read at 0x00000000a891fb3a (in kfence-#1): bpf_sk_storage_get_tracing+0x2e/0x1b0 bpf_prog_5ea3e95db6da0438_tcp_retransmit_synack+0x1d20/0x1dda bpf_trace_run2+0x4c/0xc0 tcp_rtx_synack+0xf9/0x100 reqsk_timer_handler+0xda/0x3d0 run_timer_softirq+0x292/0x8a0 irq_exit_rcu+0xf5/0x320 sysvec_apic_timer_interrupt+0x6d/0x80 asm_sysvec_apic_timer_interrupt+0x16/0x20 intel_idle_irq+0x5a/0xa0 cpuidle_enter_state+0x94/0x273 cpu_startup_entry+0x15e/0x260 start_secondary+0x8a/0x90 secondary_startup_64_no_verify+0xfa/0xfb kfence-#1: 0x00000000a72cc7b6-0x00000000d97616d9, size=2376, cache=TCPv6 allocated by task 0 on cpu 9 at 260507.901592s: sk_prot_alloc+0x35/0x140 sk_clone_lock+0x1f/0x3f0 inet_csk_clone_lock+0x15/0x160 tcp_create_openreq_child+0x1f/0x410 tcp_v6_syn_recv_sock+0x1da/0x700 tcp_check_req+0x1fb/0x510 tcp_v6_rcv+0x98b/0x1420 ipv6_list_rcv+0x2258/0x26e0 napi_complete_done+0x5b1/0x2990 mlx5e_napi_poll+0x2ae/0x8d0 net_rx_action+0x13e/0x590 irq_exit_rcu+0xf5/0x320 common_interrupt+0x80/0x90 asm_common_interrupt+0x22/0x40 cpuidle_enter_state+0xfb/0x273 cpu_startup_entry+0x15e/0x260 start_secondary+0x8a/0x90 secondary_startup_64_no_verify+0xfa/0xfb freed by task 0 on cpu 9 at 260507.927527s: rcu_core_si+0x4ff/0xf10 irq_exit_rcu+0xf5/0x320 sysvec_apic_timer_interrupt+0x6d/0x80 asm_sysvec_apic_timer_interrupt+0x16/0x20 cpuidle_enter_state+0xfb/0x273 cpu_startup_entry+0x15e/0x260 start_secondary+0x8a/0x90 secondary_startup_64_no_verify+0xfa/0xfb Thanks, Martin