From patchwork Fri Aug 19 21:42:22 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Alexei Starovoitov X-Patchwork-Id: 12949271 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id B429BC32771 for ; Fri, 19 Aug 2022 21:42:55 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 4DAE36B007B; Fri, 19 Aug 2022 17:42:55 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 463916B007D; Fri, 19 Aug 2022 17:42:55 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 2DEBF6B007E; Fri, 19 Aug 2022 17:42:55 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0013.hostedemail.com [216.40.44.13]) by kanga.kvack.org (Postfix) with ESMTP id 1D1E66B007B for ; Fri, 19 Aug 2022 17:42:55 -0400 (EDT) Received: from smtpin28.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay01.hostedemail.com (Postfix) with ESMTP id E9DD51C7678 for ; Fri, 19 Aug 2022 21:42:54 +0000 (UTC) X-FDA: 79817667468.28.AA7A67C Received: from mail-pl1-f174.google.com (mail-pl1-f174.google.com [209.85.214.174]) by imf30.hostedemail.com (Postfix) with ESMTP id 9C9A280006 for ; Fri, 19 Aug 2022 21:42:54 +0000 (UTC) Received: by mail-pl1-f174.google.com with SMTP id w14so5143296plp.9 for ; Fri, 19 Aug 2022 14:42:54 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc; bh=KAWNhWE/WD3wFZacJ2ko17zYo7gsMhvffUTmRG8how0=; b=IJU+tAgIT6VuO5vXWYEJYSrs+tbTdFc9scQFNl6/qxCoimGAqFqVKFLtfP3ORfpHRc pMymoiUer9FBhgdQ10onvBH5bPowq+J6JG09mUonw6k8A2ayOcFgskAwekWPRUCYgmss oztKP6p+IMe2wJNJifLQ68ZaYz7G53sojy2B5ky2v65akg2hOaUTmghTabkRHWQZvZna rGSAxzIyfaskEWfhv23ry3UX8LpgnOvXseZtfV+mehCvPNP2HJj144ese0DFSPJ3SrNy 8xi+X6X9qUJEsq2kzUFxG5rysq8yLSOa4aIB+30GlKaNeGCMmvFIG9+8RQRgRCS4ypyd K2QA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-message-state:from:to:cc; bh=KAWNhWE/WD3wFZacJ2ko17zYo7gsMhvffUTmRG8how0=; b=oUHByCRNmt1SQw0ZBXTa7WuwhTuzNEzzLgHPNlaErVf2UufSPtl7OUm3rqYKZpqc6/ YLiYs1OUvqKhYjxHHLivS/7xYadBFhtOhakI9msiiXQKbf7vFIaTEdCLWN2Ue6DFfcwT UTQRlRdsRnGKsBzxFy0frvYvlOS559rT1so/RM8dPUey5AxlNvvuXsTJ7NdBXNpXVNs3 HLPEymWGGtyKXgf95BPt7WSFoOIC42J+vR9ybDwmBxdPxWIaDdVYbEOgXgmxNx6oXkYy fFyTeZ0Kha/fYxsH+bfRet5+m+SFNAaXne0vPbeoXFfiwISGM0OXSNWz9iXBoBOHsJyD J+KQ== X-Gm-Message-State: ACgBeo0WNv0V0isBAelUrSlZZMXUajxnDHM7F/i2aZMfid3BPQ71hKjf fmUdD1ZC0AY8y26zX0OVbZQ= X-Google-Smtp-Source: AA6agR5imW3PqoQL8w/K4SjG7gOYKgOg1fCub6mJHTYaUIK+t9YYvXW+AavS+6d/c4j5U1tijiMk3A== X-Received: by 2002:a17:902:cf11:b0:172:6437:412e with SMTP id i17-20020a170902cf1100b001726437412emr9009830plg.77.1660945373647; Fri, 19 Aug 2022 14:42:53 -0700 (PDT) Received: from localhost.localdomain ([2620:10d:c090:500::1:c4b1]) by smtp.gmail.com with ESMTPSA id c5-20020a637245000000b0041a919ed63dsm3341084pgn.3.2022.08.19.14.42.52 (version=TLS1_3 cipher=TLS_CHACHA20_POLY1305_SHA256 bits=256/256); Fri, 19 Aug 2022 14:42:53 -0700 (PDT) From: Alexei Starovoitov To: davem@davemloft.net Cc: daniel@iogearbox.net, andrii@kernel.org, tj@kernel.org, memxor@gmail.com, delyank@fb.com, linux-mm@kvack.org, bpf@vger.kernel.org, kernel-team@fb.com Subject: [PATCH v3 bpf-next 05/15] bpf: Relax the requirement to use preallocated hash maps in tracing progs. Date: Fri, 19 Aug 2022 14:42:22 -0700 Message-Id: <20220819214232.18784-6-alexei.starovoitov@gmail.com> X-Mailer: git-send-email 2.36.1 In-Reply-To: <20220819214232.18784-1-alexei.starovoitov@gmail.com> References: <20220819214232.18784-1-alexei.starovoitov@gmail.com> MIME-Version: 1.0 ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1660945374; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=KAWNhWE/WD3wFZacJ2ko17zYo7gsMhvffUTmRG8how0=; b=b7/DDLTNqR3M37yqoW5SANGOSgrBZ92AspkXv0kgtwgcCO5lMNDziTCstO4DG4OjCMPqij R+Af7fVnrwwEgF7rj2CDAVSFEtS5e51SPRDMYfVCzLSYfjjEmipZsfVq+nzZ3FxXtafL23 jSHyzSPeEnB4VRWeaOWFhS0TPmw0vlA= ARC-Authentication-Results: i=1; imf30.hostedemail.com; dkim=pass header.d=gmail.com header.s=20210112 header.b=IJU+tAgI; spf=pass (imf30.hostedemail.com: domain of alexei.starovoitov@gmail.com designates 209.85.214.174 as permitted sender) smtp.mailfrom=alexei.starovoitov@gmail.com; dmarc=pass (policy=none) header.from=gmail.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1660945374; a=rsa-sha256; cv=none; b=WjaL040ceR93m37r3g/ZFattpRnOAT9gEgCqsyg6pLBfko91sDEdW6O9C1q6Eosk7zSC8y 5cZtshb6Y+hJKaV67AJOpRpGersUsTrD2Yj1+wx3F48QUphaYNP6z/eWP4sKMT+/HFqVFC feOQ0Vy4x035AwvfVrW82wJYLFXSuko= Authentication-Results: imf30.hostedemail.com; dkim=pass header.d=gmail.com header.s=20210112 header.b=IJU+tAgI; spf=pass (imf30.hostedemail.com: domain of alexei.starovoitov@gmail.com designates 209.85.214.174 as permitted sender) smtp.mailfrom=alexei.starovoitov@gmail.com; dmarc=pass (policy=none) header.from=gmail.com X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: 9C9A280006 X-Stat-Signature: fmobs159ytbysqo86pojgcaaky35btcj X-Rspam-User: X-HE-Tag: 1660945374-176749 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: From: Alexei Starovoitov Since bpf hash map was converted to use bpf_mem_alloc it is safe to use from tracing programs and in RT kernels. But per-cpu hash map is still using dynamic allocation for per-cpu map values, hence keep the warning for this map type. In the future alloc_percpu_gfp can be front-end-ed with bpf_mem_cache and this restriction will be completely lifted. perf_event (NMI) bpf programs have to use preallocated hash maps, because free_htab_elem() is using call_rcu which might crash if re-entered. Sleepable bpf programs have to use preallocated hash maps, because life time of the map elements is not protected by rcu_read_lock/unlock. This restriction can be lifted in the future as well. Signed-off-by: Alexei Starovoitov --- kernel/bpf/verifier.c | 31 ++++++++++++++++++++++--------- 1 file changed, 22 insertions(+), 9 deletions(-) diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index 2c1f8069f7b7..d785f29047d7 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -12605,10 +12605,12 @@ static int check_map_prog_compatibility(struct bpf_verifier_env *env, * For programs attached to PERF events this is mandatory as the * perf NMI can hit any arbitrary code sequence. * - * All other trace types using preallocated hash maps are unsafe as - * well because tracepoint or kprobes can be inside locked regions - * of the memory allocator or at a place where a recursion into the - * memory allocator would see inconsistent state. + * All other trace types using non-preallocated per-cpu hash maps are + * unsafe as well because tracepoint or kprobes can be inside locked + * regions of the per-cpu memory allocator or at a place where a + * recursion into the per-cpu memory allocator would see inconsistent + * state. Non per-cpu hash maps are using bpf_mem_alloc-tor which is + * safe to use from kprobe/fentry and in RT. * * On RT enabled kernels run-time allocation of all trace type * programs is strictly prohibited due to lock type constraints. On @@ -12618,15 +12620,26 @@ static int check_map_prog_compatibility(struct bpf_verifier_env *env, */ if (is_tracing_prog_type(prog_type) && !is_preallocated_map(map)) { if (prog_type == BPF_PROG_TYPE_PERF_EVENT) { + /* perf_event bpf progs have to use preallocated hash maps + * because non-prealloc is still relying on call_rcu to free + * elements. + */ verbose(env, "perf_event programs can only use preallocated hash map\n"); return -EINVAL; } - if (IS_ENABLED(CONFIG_PREEMPT_RT)) { - verbose(env, "trace type programs can only use preallocated hash map\n"); - return -EINVAL; + if (map->map_type == BPF_MAP_TYPE_PERCPU_HASH || + (map->inner_map_meta && + map->inner_map_meta->map_type == BPF_MAP_TYPE_PERCPU_HASH)) { + if (IS_ENABLED(CONFIG_PREEMPT_RT)) { + verbose(env, + "trace type programs can only use preallocated per-cpu hash map\n"); + return -EINVAL; + } + WARN_ONCE(1, "trace type BPF program uses run-time allocation\n"); + verbose(env, + "trace type programs with run-time allocated per-cpu hash maps are unsafe." + " Switch to preallocated hash maps.\n"); } - WARN_ONCE(1, "trace type BPF program uses run-time allocation\n"); - verbose(env, "trace type programs with run-time allocated hash maps are unsafe. Switch to preallocated hash maps.\n"); } if (map_value_has_spin_lock(map)) {