From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-0.8 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 8C527C2D0E8 for ; Thu, 26 Mar 2020 15:18:21 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 663B02073E for ; Thu, 26 Mar 2020 15:18:21 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="Zi3XtTrJ" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727967AbgCZPSV (ORCPT ); Thu, 26 Mar 2020 11:18:21 -0400 Received: from mail-pg1-f195.google.com ([209.85.215.195]:35607 "EHLO mail-pg1-f195.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727831AbgCZPSU (ORCPT ); Thu, 26 Mar 2020 11:18:20 -0400 Received: by mail-pg1-f195.google.com with SMTP id k5so813330pga.2; Thu, 26 Mar 2020 08:18:19 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=date:from:to:cc:message-id:in-reply-to:references:subject :mime-version:content-transfer-encoding; bh=SEZC5U5HCQ5IlqX3yXiHzE6xtayGr1pigC/qA5cGrz4=; b=Zi3XtTrJW4XTcmZk9BwyqxrlRqpkhuAmqXGlYq6YiVBjRH1rAxwr3d4427Pw/G81UP +0nvTFsoQjbkYW4DnmACQFyjaXt8b3YVNVHCXsVDJPUiFKo0u0bYSXu4s5qaQKWLK2nc 90Q+ERjNxwXscqwkaXn/eBxVY9bZDV5Iv7LBhYC0toVY/qDc6c96vL12hHeSsMfNN9AX dW02IVncXhypzEJUB4PLSoN2TcX8kEoQ6qvduqFK3T6CmwKoo1riq1WBsmkDKlAmVi2k cbZs8g1/RrTmZHtga2RSmtsNUYMssnM6b7/KYb6Y6DwsWqughIilAndET9YZ4OwfEbOs M6UA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:message-id:in-reply-to :references:subject:mime-version:content-transfer-encoding; bh=SEZC5U5HCQ5IlqX3yXiHzE6xtayGr1pigC/qA5cGrz4=; b=XFy1uxPLn2SfMfSlPK868L+mA61MQM5J8LBLuH5GPmRhZdFwFM1Yg3u360BeEjn1QO LVO7rAO5qyDyM+rgJYnVgq6is6EtcMNP/AbRnJhuEydIF/URy76K+cqeYFplH85NK1wz FYjegTOHqK1qudarxFOrDsLmfYwY4/riqnwLO7G1IllLaf2aSvYD6dD1wfUAniYLCdIw 2zEvEOIbNdD+0+9euimvRCYeT9OVk//W5FFNPhvq4dKZUkdro2AzMm1ggmDwMgInoOMG Mov/ZLoWWI6pLNVZ9vC3E9HrqLnon3LDI+Fw/iNNtKNtHpRKtNlt8DBLNx54rRUQKW4F 6M5A== X-Gm-Message-State: ANhLgQ1dHL5c30wMTqyFMfAjrdfL7zJ3dNqDdslBLq505heKWNOOfNw3 Ra8UGu1UT11sOUSbZVpzfXc= X-Google-Smtp-Source: ADFU+vsGMzB74d9mC7lMP9fOJflkiV1YjB5mUHEiruJPCDJIkj5abfouqcJAfz3kJIYkohTQoAR69Q== X-Received: by 2002:a65:5b49:: with SMTP id y9mr8839684pgr.153.1585235899316; Thu, 26 Mar 2020 08:18:19 -0700 (PDT) Received: from localhost ([184.63.162.180]) by smtp.gmail.com with ESMTPSA id c15sm1925026pfo.139.2020.03.26.08.18.16 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 26 Mar 2020 08:18:18 -0700 (PDT) Date: Thu, 26 Mar 2020 08:18:09 -0700 From: John Fastabend To: Alexei Starovoitov , John Fastabend Cc: ecree@solarflare.com, yhs@fb.com, daniel@iogearbox.net, netdev@vger.kernel.org, bpf@vger.kernel.org Message-ID: <5e7cc7b15c012_65132acbbe7fc5c4e9@john-XPS-13-9370.notmuch> In-Reply-To: <20200326062001.3j6yqyu7jne4gtfl@ast-mbp> References: <158507130343.15666.8018068546764556975.stgit@john-Precision-5820-Tower> <158507153582.15666.3091405867682349273.stgit@john-Precision-5820-Tower> <20200326062001.3j6yqyu7jne4gtfl@ast-mbp> Subject: Re: [bpf-next PATCH 04/10] bpf: verifier, do explicit ALU32 bounds tracking Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org Alexei Starovoitov wrote: > On Tue, Mar 24, 2020 at 10:38:56AM -0700, John Fastabend wrote: > > -static void __reg_bound_offset32(struct bpf_reg_state *reg) > > +static void __reg_combine_32_into_64(struct bpf_reg_state *reg) > > { > > - u64 mask = 0xffffFFFF; > > - struct tnum range = tnum_range(reg->umin_value & mask, > > - reg->umax_value & mask); > > - struct tnum lo32 = tnum_cast(reg->var_off, 4); > > - struct tnum hi32 = tnum_lshift(tnum_rshift(reg->var_off, 32), 32); > > + /* special case when 64-bit register has upper 32-bit register > > + * zeroed. Typically happens after zext or <<32, >>32 sequence > > + * allowing us to use 32-bit bounds directly, > > + */ > > + if (tnum_equals_const(tnum_clear_subreg(reg->var_off), 0)) { > > + reg->umin_value = reg->u32_min_value; > > + reg->umax_value = reg->u32_max_value; > > + reg->smin_value = reg->s32_min_value; > > + reg->smax_value = reg->s32_max_value; > > Looks like above will not be correct for negative s32_min/max. > When upper 32-bit are cleared and we're processing jmp32 > we cannot set smax_value to s32_max_value. > Consider if (w0 s< -5) > s32_max_value == -5 > which is 0xfffffffb > but upper 32 are zeros so smax_value should be (u64)0xfffffffb > and not (s64)-5 Right, good catch. I'll use below logic here as well. > > We can be fancy and precise with this logic, but I would just use similar > approach from zext_32_to_64() where the following: > + if (reg->s32_min_value > 0) > + reg->smin_value = reg->s32_min_value; > + else > + reg->smin_value = 0; > + if (reg->s32_max_value > 0) > + reg->smax_value = reg->s32_max_value; > + else > + reg->smax_value = U32_MAX; > should work for this case too ? > > > + if (BPF_SRC(insn->code) == BPF_K) { > > + pred = is_branch_taken(dst_reg, insn->imm, opcode, is_jmp32); > > + } else if (src_reg->type == SCALAR_VALUE && is_jmp32 && tnum_is_const(tnum_subreg(src_reg->var_off))) { > > + pred = is_branch_taken(dst_reg, tnum_subreg(src_reg->var_off).value, opcode, is_jmp32); > > + } else if (src_reg->type == SCALAR_VALUE && !is_jmp32 && tnum_is_const(src_reg->var_off)) { > > + pred = is_branch_taken(dst_reg, src_reg->var_off.value, opcode, is_jmp32); > > + } > > pls wrap these lines. Way above normal. +1 > > The rest is awesome. Thanks.