From patchwork Wed Oct 25 07:59:12 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Chuyi Zhou X-Patchwork-Id: 13435682 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 3C3E71C2BA for ; Wed, 25 Oct 2023 08:00:23 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=bytedance.com header.i=@bytedance.com header.b="c63pA3MJ" Received: from mail-oi1-x22b.google.com (mail-oi1-x22b.google.com [IPv6:2607:f8b0:4864:20::22b]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 5902C10E for ; Wed, 25 Oct 2023 01:00:22 -0700 (PDT) Received: by mail-oi1-x22b.google.com with SMTP id 5614622812f47-3b2e72fe47fso3592068b6e.1 for ; Wed, 25 Oct 2023 01:00:22 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=bytedance.com; s=google; t=1698220821; x=1698825621; 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=623dJ/e0dl/9VZB/F0AUPvisvbBwnO9eeoKfg40DawY=; b=c63pA3MJG1VO2lYZk8GDp+mZCt1iE8qhQ5+IB54LTPEf0f/k4Sms99qsgZHDegM3U8 KTH9mYiN73PzC2cswq1qZnVq9OHwJLgV36A8usJRNvaNQ1Ivm3FcKUCTOH6gEicgtRfa o4pZuOuXs/7lzH6imA8D/J+/jLiw50A1m3856GkumU719qGHD0n4meBCHzYxJFrYwF1B ktkMEuSXuL65oXLgd199xPhdFUdaj5tbVxNj2uorIlTu4xh/p8Sij6xDZCfUFrlA++mV tG+hc5wL/tSA5CSWxyRgZ+NWrfz0AVbiSEcZnbBJ0Ne1ixzeYv2Zn+MnI6SMxexFHZQb sraQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1698220821; x=1698825621; 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=623dJ/e0dl/9VZB/F0AUPvisvbBwnO9eeoKfg40DawY=; b=t4GnpcLZglCTkKR+FdZSEznlb82EUbLFUW+YOYrkKUzDnm9Cf8mXjwHGd8aGyipZMf L3maEWN6VMrcFm8saYZ2f//xqgPxGZonf2cJIRzOa2mytZV2mzwqP/HkqQbSYfMJVZ06 bKwaYNY6BSzOybqQNP8UrUqi2Xue5KIFULX+GE/uxBKpDrwQiTMN7aC+DzkOCr2CmtyM /nh4HUIEDbiMInVcyXZCLvDYsEm09K9Nk8FoMpFyazKMREfgH4F2yzz8tPy8WIOZ1R+N tla+XiR7L9R3s4xUtuPJPZUSmRf7IWWrJ+jVA39NnknkJ/vtpHawivqTXxXaFydgVtim GX6g== X-Gm-Message-State: AOJu0YxmNczC9wDcc4N7C18F1T4gkxEdv95tcOpQ1ansfHV+G8ua62Qh GCK2UpycVd1FRHgThwH1Wwb5xRUfgq4B1PJYbPg= X-Google-Smtp-Source: AGHT+IFNrJ6aGXsfBcfq42K58SlpCq4ESlrfgv2CoCJH4pDIc90B4PFXLHn+X0N/+cKUV52sXWfNgA== X-Received: by 2002:a05:6808:3ce:b0:3ae:55e5:43b6 with SMTP id o14-20020a05680803ce00b003ae55e543b6mr13588579oie.48.1698220821013; Wed, 25 Oct 2023 01:00:21 -0700 (PDT) Received: from n37-019-243.byted.org ([180.184.51.40]) by smtp.gmail.com with ESMTPSA id 23-20020a630f57000000b0059cc2f1b7basm8118187pgp.11.2023.10.25.01.00.19 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 25 Oct 2023 01:00:20 -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 v3 1/3] bpf: Relax allowlist for css_task iter Date: Wed, 25 Oct 2023 15:59:12 +0800 Message-Id: <20231025075914.30979-2-zhouchuyi@bytedance.com> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20231025075914.30979-1-zhouchuyi@bytedance.com> References: <20231025075914.30979-1-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 Acked-by: Yonghong Song --- kernel/bpf/verifier.c | 16 ++++++++++++---- .../selftests/bpf/progs/iters_task_failure.c | 4 ++-- 2 files changed, 14 insertions(+), 6 deletions(-) diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index e9bc5d4a25a1..9243b6ca4854 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -11088,6 +11088,12 @@ 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); @@ -11095,10 +11101,12 @@ static bool check_css_task_iter_allowlist(struct bpf_verifier_env *env) switch (prog_type) { case BPF_PROG_TYPE_LSM: return true; - case BPF_TRACE_ITER: - return env->prog->aux->sleepable; + case BPF_PROG_TYPE_TRACING: + if (env->prog->expected_attach_type == BPF_TRACE_ITER) + return true; + fallthrough; default: - return false; + return env->prog->aux->sleepable; } } @@ -11357,7 +11365,7 @@ 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();