From patchwork Thu Oct 5 08:39:52 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Yafang Shao X-Patchwork-Id: 13409866 X-Patchwork-Delegate: bpf@iogearbox.net Received: from lindbergh.monkeyblade.net (lindbergh.monkeyblade.net [23.128.96.19]) (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 5F3AF538C for ; Thu, 5 Oct 2023 08:39:59 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="YGBrj8LM" Received: from mail-ot1-x32a.google.com (mail-ot1-x32a.google.com [IPv6:2607:f8b0:4864:20::32a]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C8528900A for ; Thu, 5 Oct 2023 01:39:57 -0700 (PDT) Received: by mail-ot1-x32a.google.com with SMTP id 46e09a7af769-6c4d625da40so507311a34.1 for ; Thu, 05 Oct 2023 01:39:57 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20230601; t=1696495197; x=1697099997; darn=vger.kernel.org; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:from:to:cc:subject:date:message-id:reply-to; bh=Md4/gNXefd/DLZFJxe4EWoi04i8hmvyR0NPZMEvk15U=; b=YGBrj8LMIFuE9Z7x8lwWSkk2TxYQGJYVecGq003nNbxHpafcCQoMIQxNe3ZpgruOQn MRkCO6ukHc0QYArvdfev/lH5afrSYHfLGQKb6mQPgN6amYYVEOS8/EOy0siWZg5gLSHQ aeBcFStvl+UTpu8wkHYZZHxtnSjI99u2JGN1j3JHz/HUzHoMF874WMoCZ7lZ9wTniJcO E0fQ+H7e7ksywv3uI143iWYzmnnoNPd9Per7M0jIpSdJEfeV3Zm+RLcwYE+bm1vz1+uK 3qrf9ezwNJOY+Hmas3uBM/MBooZLUJ0dWNbKnAZZxgGOGqveGM/xzU6O0rmPSJ3HSOuc uTsA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1696495197; x=1697099997; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:x-gm-message-state:from:to:cc:subject:date:message-id :reply-to; bh=Md4/gNXefd/DLZFJxe4EWoi04i8hmvyR0NPZMEvk15U=; b=Ky9dzK2eK5sgAVSMFYnz55lZ5fexoZmtHBnD1RzQ2YpDOM8n4BBKZesy7TynAhQ//9 eWfPpjegkDq896KNNyAU13YELs29qBVXUZ1QUNkIAjzhrnKCpcTj/gpbZEeUtNSXV7ok 7Vq4tabMXLTjPn2glIVfB6zux3MItS0YJ8YBfpy8lJIOUqWbZ1GxZ4sqsQyFXzp4b3Rf QYycEJ7UIQ6kDTZcniaoMQZU0T4pnedgEuxuQ5faFoBjymnn9I3eyUq4vH02IGyln742 EljnRsWWeyOsgyz/eFtwu57aLhoFgdA6aaUqSeI/Sb8cY7eChuQlfHGoQGoF7ledYW2X 3y3g== X-Gm-Message-State: AOJu0YzTBFyvxSRSXhBWpdMgoSjMHz4oSzot261CRtEKKBzYM1hbWHNs RrPSdo3XUemLJp+sVgyS1Dk= X-Google-Smtp-Source: AGHT+IHGdaSqWTHMMM1pNDu7gNlQK1SHc2yw9EB0Y75tyI7GFsQC6mxUpEUzjFEmLOU71EEwwHME4Q== X-Received: by 2002:a05:6870:911e:b0:1dd:7f3a:b8ee with SMTP id o30-20020a056870911e00b001dd7f3ab8eemr5170515oae.20.1696495197002; Thu, 05 Oct 2023 01:39:57 -0700 (PDT) Received: from vultr.guest ([2001:19f0:ac00:4fd4:5400:4ff:fe99:6afd]) by smtp.gmail.com with ESMTPSA id n20-20020a638f14000000b00563e1ef0491sm924755pgd.8.2023.10.05.01.39.55 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 05 Oct 2023 01:39:56 -0700 (PDT) From: Yafang Shao To: ast@kernel.org, daniel@iogearbox.net, john.fastabend@gmail.com, andrii@kernel.org, martin.lau@linux.dev, song@kernel.org, yonghong.song@linux.dev, kpsingh@kernel.org, sdf@google.com, haoluo@google.com, jolsa@kernel.org Cc: bpf@vger.kernel.org, Yafang Shao , Feng Zhou Subject: [PATCH bpf-next 1/2] bpf: Fix missed rcu read lock in bpf_task_under_cgroup() Date: Thu, 5 Oct 2023 08:39:52 +0000 Message-Id: <20231005083953.1281-1-laoar.shao@gmail.com> X-Mailer: git-send-email 2.39.3 Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Spam-Status: No, score=-2.1 required=5.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,FREEMAIL_FROM, RCVD_IN_DNSWL_BLOCKED,SPF_HELO_NONE,SPF_PASS autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net X-Patchwork-Delegate: bpf@iogearbox.net When employed within a sleepable program not under RCU protection, the use of 'bpf_task_under_cgroup()' may trigger a warning in the kernel log, particularly when CONFIG_PROVE_RCU is enabled. [ 1259.662354] ============================= [ 1259.662357] WARNING: suspicious RCU usage [ 1259.662358] 6.5.0+ #33 Not tainted [ 1259.662360] ----------------------------- [ 1259.662361] include/linux/cgroup.h:423 suspicious rcu_dereference_check() usage! [ 1259.662364] other info that might help us debug this: [ 1259.662366] rcu_scheduler_active = 2, debug_locks = 1 [ 1259.662368] 1 lock held by trace/72954: [ 1259.662369] #0: ffffffffb5e3eda0 (rcu_read_lock_trace){....}-{0:0}, at: __bpf_prog_enter_sleepable+0x0/0xb0 [ 1259.662383] stack backtrace: [ 1259.662385] CPU: 50 PID: 72954 Comm: trace Kdump: loaded Not tainted 6.5.0+ #33 [ 1259.662391] Call Trace: [ 1259.662393] [ 1259.662395] dump_stack_lvl+0x6e/0x90 [ 1259.662401] dump_stack+0x10/0x20 [ 1259.662404] lockdep_rcu_suspicious+0x163/0x1b0 [ 1259.662412] task_css_set.part.0+0x23/0x30 [ 1259.662417] bpf_task_under_cgroup+0xe7/0xf0 [ 1259.662422] bpf_prog_7fffba481a3bcf88_lsm_run+0x5c/0x93 [ 1259.662431] bpf_trampoline_6442505574+0x60/0x1000 [ 1259.662439] bpf_lsm_bpf+0x5/0x20 [ 1259.662443] ? security_bpf+0x32/0x50 [ 1259.662452] __sys_bpf+0xe6/0xdd0 [ 1259.662463] __x64_sys_bpf+0x1a/0x30 [ 1259.662467] do_syscall_64+0x38/0x90 [ 1259.662472] entry_SYSCALL_64_after_hwframe+0x6e/0xd8 [ 1259.662479] RIP: 0033:0x7f487baf8e29 ... [ 1259.662504] This issue can be reproduced by executing a straightforward program, as demonstrated below: SEC("lsm.s/bpf") int BPF_PROG(lsm_run, int cmd, union bpf_attr *attr, unsigned int size) { struct cgroup *cgrp = NULL; struct task_struct *task; int ret = 0; if (cmd != BPF_LINK_CREATE) return 0; // The cgroup2 should be mounted first cgrp = bpf_cgroup_from_id(1); if (!cgrp) goto out; task = bpf_get_current_task_btf(); if (bpf_task_under_cgroup(task, cgrp)) ret = -1; bpf_cgroup_release(cgrp); out: return ret; } After running the program, if you subsequently execute another BPF program, you will encounter the warning. It's worth noting that task_under_cgroup_hierarchy() is also utilized by bpf_current_task_under_cgroup(). However, bpf_current_task_under_cgroup() doesn't exhibit this issue because it cannot be used in sleepable BPF programs. Fixes: b5ad4cdc46c7 ("bpf: Add bpf_task_under_cgroup() kfunc") Signed-off-by: Yafang Shao Cc: Feng Zhou --- kernel/bpf/helpers.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c index dd1c69e..bb521b1 100644 --- a/kernel/bpf/helpers.c +++ b/kernel/bpf/helpers.c @@ -2212,7 +2212,12 @@ __bpf_kfunc struct cgroup *bpf_cgroup_from_id(u64 cgid) __bpf_kfunc long bpf_task_under_cgroup(struct task_struct *task, struct cgroup *ancestor) { - return task_under_cgroup_hierarchy(task, ancestor); + long ret; + + rcu_read_lock(); + ret = task_under_cgroup_hierarchy(task, ancestor); + rcu_read_unlock(); + return ret; } #endif /* CONFIG_CGROUPS */