From patchwork Sun Oct 22 15:45:26 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Chuyi Zhou X-Patchwork-Id: 13431877 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 1A2093D6B for ; Sun, 22 Oct 2023 15:45:43 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=bytedance.com header.i=@bytedance.com header.b="EhuJOH9a" Received: from mail-pg1-x52e.google.com (mail-pg1-x52e.google.com [IPv6:2607:f8b0:4864:20::52e]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 8904DB4 for ; Sun, 22 Oct 2023 08:45:41 -0700 (PDT) Received: by mail-pg1-x52e.google.com with SMTP id 41be03b00d2f7-5ad5178d1bfso1799881a12.2 for ; Sun, 22 Oct 2023 08:45:41 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=bytedance.com; s=google; t=1697989541; x=1698594341; darn=vger.kernel.org; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc:subject:date :message-id:reply-to; bh=6GGyfh+aKWvGCG4k2jaPd37bFIq+IpE0RtBXZgW8v20=; b=EhuJOH9aptDiVYftAuJmORpJPgrzDefiSs5HtTUMtmCiTA3MXrglEJ34XcZX2OUg+I 7S1KNHaAlD7WWYpwEEVWAlbsefFrrOK3CKh0qA4WJ4YTOcYSwh85AaF4/va3Rs6uX4cc rSwV59GgWWGaE7EqLzes75NcDrBdy+ox/9rmvnJe8ZtDzaBaRDMXjuZ7D8bt09EpAShV NwY37oMka9/JOyk3Vyoc0oNtZGayXIShHD0e78pzQiaGuHrsKMAQW3/i3V+PTqBw6Kbd E0x4L5d/4dmervMnqcMhh7ag+YqqCTSvwHuDkZd9xiuAn5n9Ngt/9n9QJKDhFhBeK/RU j8YQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1697989541; x=1698594341; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=6GGyfh+aKWvGCG4k2jaPd37bFIq+IpE0RtBXZgW8v20=; b=iF0ZZgzUvrGmjx4VPI1/U10pw0T4BwHNZfFKsBkEM+Z6TCatdvl+gUwqPZkuIvAagJ tsq3viM6Ldjobmts/K6ZB69RWXdLDTG/Vh92vQKFX4bsIZSDa2i8CoQgR8Ts8nStR1Zh QsyYdcU0WKuDY6lRrxpDAuss3jHHAvEnvz9HB8cqcMZDI5ofoFceYZzYQpAuJFglh/KD 7/q4pg5zmrV7Fr/+0ZATNQt/5nxbglA/6WpTZ7Z6jDAwRlY9U3RipW6hwUQTr1RUm2SX h/n4nZD28/2r7jz0KUDDfPqbtmutNJBMfMd8SJUzoFmPrTrjVrehlRefxaouy4EwUA80 2DRQ== X-Gm-Message-State: AOJu0YyWaw22jwv8BBwPeUA4euEhzjm7GVUJNs/cHgHH/Y9hJ/QB64HI RWJdQkuc0LwsSubZ9bOQWoOtRtUocWJLkDhObfudJw== X-Google-Smtp-Source: AGHT+IGKMEs4q9CS5ZZrpi1jgS9Yq1U9mCk7eBuxH0i1DXmeNOFq4B7xceyPETqz5tNmaxQF0Q+xsw== X-Received: by 2002:a17:902:eb8e:b0:1c9:cc88:502c with SMTP id q14-20020a170902eb8e00b001c9cc88502cmr8897886plg.69.1697989540897; Sun, 22 Oct 2023 08:45:40 -0700 (PDT) Received: from n37-019-243.byted.org ([180.184.49.4]) by smtp.gmail.com with ESMTPSA id l2-20020a170902d34200b001bbdd44bbb6sm4551996plk.136.2023.10.22.08.45.38 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 22 Oct 2023 08:45:40 -0700 (PDT) From: Chuyi Zhou To: bpf@vger.kernel.org Cc: ast@kernel.org, daniel@iogearbox.net, andrii@kernel.org, martin.lau@kernel.org, Chuyi Zhou Subject: [PATCH bpf-next 1/2] bpf: Relax allowlist for css_task iter Date: Sun, 22 Oct 2023 23:45:26 +0800 Message-Id: <20231022154527.229117-2-zhouchuyi@bytedance.com> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20231022154527.229117-1-zhouchuyi@bytedance.com> References: <20231022154527.229117-1-zhouchuyi@bytedance.com> Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Patchwork-Delegate: bpf@iogearbox.net The newly added open-coded css_task iter would try to hold the global css_set_lock in bpf_iter_css_task_new, so the bpf side has to be careful in where it allows to use this iter. The mainly concern is dead locking on css_set_lock. check_css_task_iter_allowlist() in verifier enforced css_task can only be used in bpf_lsm hooks and sleepable bpf_iter. This patch relax the allowlist for css_task iter. Any lsm and any iter (even non-sleepable) and any sleepable are safe since they would not hold the css_set_lock before entering BPF progs context. This patch also fixes the misused BPF_TRACE_ITER in check_css_task_iter_allowlist which compared bpf_prog_type with bpf_attach_type. Fixes: 9c66dc94b62ae ("bpf: Introduce css_task open-coded iterator kfuncs") Signed-off-by: Chuyi Zhou --- kernel/bpf/verifier.c | 15 ++++++++++----- .../selftests/bpf/progs/iters_task_failure.c | 4 ++-- 2 files changed, 12 insertions(+), 7 deletions(-) diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index e9bc5d4a25a1..cc79cd555337 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -11088,17 +11088,22 @@ static int process_kf_arg_ptr_to_rbtree_node(struct bpf_verifier_env *env, &meta->arg_rbtree_root.field); } +/* + * css_task iter allowlist is needed to avoid dead locking on css_set_lock. + * LSM hooks and iters (both sleepable and non-sleepable) are safe. + * Any sleepable progs are also safe since bpf_check_attach_target() enforce + * them can only be attached to some specific hook points. + */ static bool check_css_task_iter_allowlist(struct bpf_verifier_env *env) { enum bpf_prog_type prog_type = resolve_prog_type(env->prog); - switch (prog_type) { case BPF_PROG_TYPE_LSM: return true; - case BPF_TRACE_ITER: - return env->prog->aux->sleepable; + case BPF_PROG_TYPE_TRACING: + return env->prog->expected_attach_type == BPF_TRACE_ITER; default: - return false; + return env->prog->aux->sleepable; } } @@ -11357,7 +11362,7 @@ static int check_kfunc_args(struct bpf_verifier_env *env, struct bpf_kfunc_call_ case KF_ARG_PTR_TO_ITER: if (meta->func_id == special_kfunc_list[KF_bpf_iter_css_task_new]) { if (!check_css_task_iter_allowlist(env)) { - verbose(env, "css_task_iter is only allowed in bpf_lsm and bpf iter-s\n"); + verbose(env, "css_task_iter is only allowed in bpf_lsm, bpf_iter and sleepable progs\n"); return -EINVAL; } } diff --git a/tools/testing/selftests/bpf/progs/iters_task_failure.c b/tools/testing/selftests/bpf/progs/iters_task_failure.c index c3bf96a67dba..6b1588d70652 100644 --- a/tools/testing/selftests/bpf/progs/iters_task_failure.c +++ b/tools/testing/selftests/bpf/progs/iters_task_failure.c @@ -84,8 +84,8 @@ int BPF_PROG(iter_css_lock_and_unlock) return 0; } -SEC("?fentry.s/" SYS_PREFIX "sys_getpgid") -__failure __msg("css_task_iter is only allowed in bpf_lsm and bpf iter-s") +SEC("?fentry/" SYS_PREFIX "sys_getpgid") +__failure __msg("css_task_iter is only allowed in bpf_lsm, bpf_iter and sleepable progs") int BPF_PROG(iter_css_task_for_each) { u64 cg_id = bpf_get_current_cgroup_id();