From patchwork Mon Oct 14 22:33:12 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Kuniyuki Iwashima X-Patchwork-Id: 13835533 X-Patchwork-Delegate: kuba@kernel.org Received: from smtp-fw-2101.amazon.com (smtp-fw-2101.amazon.com [72.21.196.25]) (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 E30E01D014A for ; Mon, 14 Oct 2024 22:33:24 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=72.21.196.25 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1728945209; cv=none; b=fwAytnpGzZV7dMo2TC1cRgxGz1u2ZfV9SlvwWziOR9UaGe9PCS7e5SinuH8BjWlrBy1+uORmIRJD16tV91km0fGn+olMakEhtyboqXT+bFWHJcFweutBDJrh9KnJ3Ln8cP0vW5c5T4ZkWKTY+dozoB517lyJKwsl7ppwENLKH8A= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1728945209; c=relaxed/simple; bh=2VWMoBRBIDcYUGtyngISg3880Nrxydo5SLILwpftzk4=; h=From:To:CC:Subject:Date:Message-ID:MIME-Version:Content-Type; b=NHK2s5sIaBwumaeixUEKbb3b0QEPLL/rA4rATCPoI49Bbc9TW88qp+aBzuuPnWUgIfEAvjq8l/Qe9G8bZAZvTzJV3EDFVBZV98X8BAKszO+xE5CThsjykep+qNzDvwsn50i031J5GJdpE4dKnAo8DR6yl4865WM706bfN6q5Cdo= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=amazon.com; spf=pass smtp.mailfrom=amazon.co.jp; dkim=pass (1024-bit key) header.d=amazon.com header.i=@amazon.com header.b=JnahGPuo; arc=none smtp.client-ip=72.21.196.25 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=amazon.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=amazon.co.jp Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=amazon.com header.i=@amazon.com header.b="JnahGPuo" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=amazon.com; i=@amazon.com; q=dns/txt; s=amazon201209; t=1728945205; x=1760481205; h=from:to:cc:subject:date:message-id:mime-version: content-transfer-encoding; bh=PAcyHWJfnv40eFQmF0oQpaBAy5oYKfOIavgrBC6T1ks=; b=JnahGPuoup+2WQ14erjOBsybgG8s3dpNpG77B3WQ+zn9O9FqUB14WAFe OnskOgn9ciBF/QStHmIDpnHJ3ZRh+p5gm3vY4cOVUF5EexgBNGh9sL11M pVRVyO+SODwBu7AjbQ4mD7P6qLyJG+8TO6ML2hLV9lKxJsJGLSewXtWMo s=; X-IronPort-AV: E=Sophos;i="6.11,203,1725321600"; d="scan'208";a="435048529" Received: from iad12-co-svc-p1-lb1-vlan3.amazon.com (HELO smtpout.prod.us-west-2.prod.farcaster.email.amazon.dev) ([10.43.8.6]) by smtp-border-fw-2101.iad2.amazon.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 14 Oct 2024 22:33:21 +0000 Received: from EX19MTAUWA001.ant.amazon.com [10.0.38.20:38540] by smtpin.naws.us-west-2.prod.farcaster.email.amazon.dev [10.0.49.108:2525] with esmtp (Farcaster) id 4d01e443-8abf-4581-90dd-6c8b7a92e880; Mon, 14 Oct 2024 22:33:21 +0000 (UTC) X-Farcaster-Flow-ID: 4d01e443-8abf-4581-90dd-6c8b7a92e880 Received: from EX19D004ANA001.ant.amazon.com (10.37.240.138) by EX19MTAUWA001.ant.amazon.com (10.250.64.218) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA) id 15.2.1258.34; Mon, 14 Oct 2024 22:33:20 +0000 Received: from 6c7e67c6786f.amazon.com (10.106.101.44) by EX19D004ANA001.ant.amazon.com (10.37.240.138) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA) id 15.2.1258.35; Mon, 14 Oct 2024 22:33:17 +0000 From: Kuniyuki Iwashima To: "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , David Ahern CC: Martin KaFai Lau , Kuniyuki Iwashima , Kuniyuki Iwashima , Subject: [PATCH v3 net] tcp/dccp: Don't use timer_pending() in reqsk_queue_unlink(). Date: Mon, 14 Oct 2024 15:33:12 -0700 Message-ID: <20241014223312.4254-1-kuniyu@amazon.com> X-Mailer: git-send-email 2.39.5 (Apple Git-154) Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-ClientProxiedBy: EX19D044UWB003.ant.amazon.com (10.13.139.168) To EX19D004ANA001.ant.amazon.com (10.37.240.138) X-Patchwork-Delegate: kuba@kernel.org Martin KaFai Lau reported use-after-free [0] in reqsk_timer_handler(). """ 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. """ The commit 83fccfc3940c ("inet: fix potential deadlock in reqsk_queue_unlink()") added timer_pending() in reqsk_queue_unlink() not to call del_timer_sync() from reqsk_timer_handler(), but it introduced a small race window. Before the timer is called, expire_timers() calls detach_timer(timer, true) to clear timer->entry.pprev and marks it as not pending. If reqsk_queue_unlink() checks timer_pending() just after expire_timers() calls detach_timer(), TCP will miss del_timer_sync(); the reqsk timer will continue running and send multiple SYN+ACKs until it expires. The reported UAF could happen if req->sk is close()d earlier than the timer expiration, which is 63s by default. The scenario would be 1. inet_csk_complete_hashdance() calls inet_csk_reqsk_queue_drop(), but del_timer_sync() is missed 2. reqsk timer is executed and scheduled again 3. req->sk is accept()ed and reqsk_put() decrements rsk_refcnt, but reqsk timer still has another one, and inet_csk_accept() does not clear req->sk for non-TFO sockets 4. sk is close()d 5. reqsk timer is executed again, and BPF touches req->sk Let's not use timer_pending() by passing the caller context to __inet_csk_reqsk_queue_drop(). Note that reqsk timer is pinned, so the issue does not happen in most use cases. [1] [0] 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 Fixes: 83fccfc3940c ("inet: fix potential deadlock in reqsk_queue_unlink()") Reported-by: Martin KaFai Lau Closes: https://lore.kernel.org/netdev/eb6684d0-ffd9-4bdc-9196-33f690c25824@linux.dev/ Link: https://lore.kernel.org/netdev/b55e2ca0-42f2-4b7c-b445-6ffd87ca74a0@linux.dev/ [1] Signed-off-by: Kuniyuki Iwashima Reviewed-by: Eric Dumazet Reviewed-by: Martin KaFai Lau --- v3: * Stop timer before reqsk_queue_removed(). v2: https://lore.kernel.org/netdev/20241009174226.7738-1-kuniyu@amazon.com/ * Added issue scenario in changelog * Correct reqsk for __inet_csk_reqsk_queue_drop() v1: https://lore.kernel.org/netdev/20241007141557.14424-1-kuniyu@amazon.com/ --- net/ipv4/inet_connection_sock.c | 21 ++++++++++++++++----- 1 file changed, 16 insertions(+), 5 deletions(-) diff --git a/net/ipv4/inet_connection_sock.c b/net/ipv4/inet_connection_sock.c index 2c5632d4fddb..2b698f8419fe 100644 --- a/net/ipv4/inet_connection_sock.c +++ b/net/ipv4/inet_connection_sock.c @@ -1045,21 +1045,31 @@ static bool reqsk_queue_unlink(struct request_sock *req) found = __sk_nulls_del_node_init_rcu(sk); spin_unlock(lock); } - if (timer_pending(&req->rsk_timer) && del_timer_sync(&req->rsk_timer)) - reqsk_put(req); + return found; } -bool inet_csk_reqsk_queue_drop(struct sock *sk, struct request_sock *req) +static bool __inet_csk_reqsk_queue_drop(struct sock *sk, + struct request_sock *req, + bool from_timer) { bool unlinked = reqsk_queue_unlink(req); + if (!from_timer && timer_delete_sync(&req->rsk_timer)) + reqsk_put(req); + if (unlinked) { reqsk_queue_removed(&inet_csk(sk)->icsk_accept_queue, req); reqsk_put(req); } + return unlinked; } + +bool inet_csk_reqsk_queue_drop(struct sock *sk, struct request_sock *req) +{ + return __inet_csk_reqsk_queue_drop(sk, req, false); +} EXPORT_SYMBOL(inet_csk_reqsk_queue_drop); void inet_csk_reqsk_queue_drop_and_put(struct sock *sk, struct request_sock *req) @@ -1152,7 +1162,7 @@ static void reqsk_timer_handler(struct timer_list *t) if (!inet_ehash_insert(req_to_sk(nreq), req_to_sk(oreq), NULL)) { /* delete timer */ - inet_csk_reqsk_queue_drop(sk_listener, nreq); + __inet_csk_reqsk_queue_drop(sk_listener, nreq, true); goto no_ownership; } @@ -1178,7 +1188,8 @@ static void reqsk_timer_handler(struct timer_list *t) } drop: - inet_csk_reqsk_queue_drop_and_put(oreq->rsk_listener, oreq); + __inet_csk_reqsk_queue_drop(sk_listener, oreq, true); + reqsk_put(req); } static bool reqsk_queue_hash_req(struct request_sock *req,