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 1F794C2D0E8 for ; Thu, 26 Mar 2020 06:20:07 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id EB43220719 for ; Thu, 26 Mar 2020 06:20:06 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="FWSCX9Ro" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726346AbgCZGUG (ORCPT ); Thu, 26 Mar 2020 02:20:06 -0400 Received: from mail-pl1-f193.google.com ([209.85.214.193]:33824 "EHLO mail-pl1-f193.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725819AbgCZGUG (ORCPT ); Thu, 26 Mar 2020 02:20:06 -0400 Received: by mail-pl1-f193.google.com with SMTP id a23so1764715plm.1; Wed, 25 Mar 2020 23:20:05 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=+ZCGtSDMsBtgLK1oFmDORsD6pY1gZ74q25ptizguQB8=; b=FWSCX9RoaQ5jq6EpMd3LoviH6SdOAHmcEA6PYzCpBwgffZFdIeB6hXOSIs5S3nRHDi JfqyiSr7hdY4WNT4oUI8cbZhkTfI2YCmZM5N0OOxmQlHF5WB79ZDw8fH3YEHP4jdxhgy wtfiXRapmWdPRXd6Nl85MsTfvvNQhed+ysMCJCPgpIHM+gk0DmP+xEQKDPtnlcAAYJtk tquYu0kH+zA+p/xLP7sMYbFsmumvAMse+iiVzkDUA+r2bPkg0fegm+AuwcIqvI70kzPz nA3ob+UM3lCkJ/uAGz2FisDQukuqRCHQdyqoIat4+j2QgLr7gmibzX4E1ZKUE97Cf3I4 jjGg== 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:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=+ZCGtSDMsBtgLK1oFmDORsD6pY1gZ74q25ptizguQB8=; b=WY+yV8smVAm7Tbm0yE0tZYVwLyd8VtamApkJA4ogeU0BneyF9ZhhFWKmq7AeyU2xsm ZeB/Ii8UWwdfR4EfD1Z/owCg/PU0wwsh2Az8QhgzQFM+JYh1r00YmpnSkTL8CDRl/KA1 +Rz66N+W7FS/QiL6VY8c3ZNinatJCfTGi9pXnZidgmzGHGphkOFVfDgMu4UjSl/f+wzX Uu4TB2Sq6yy/7cDFgzkohKvNR7Z1tD3HX+TOO+FJ2L/A3/0QotCbpy1Opvmo821Zg34e QVg1VA5Oy/fzIpmwwO2L1KGRAKuXL/QxHeJARn5mwinmGJg0D++J4JWgxQ2kJyDAqpYs A6bQ== X-Gm-Message-State: ANhLgQ1He76+/WPwTr3SB3ecrSZw6iHFzx2BUceq5MBBt3Tj2JZ1eNpz rkonTkfSXLxhV3G54B7FPNL2rDqR X-Google-Smtp-Source: ADFU+vs1UdS9a2vD4zOQ3PRbjSa5yFDnEIJ1E+cfQP39JTYVv2glbQUBdvBfQLIMKdtF7+Hl0OiSVA== X-Received: by 2002:a17:902:ee4b:: with SMTP id 11mr6711091plo.19.1585203604879; Wed, 25 Mar 2020 23:20:04 -0700 (PDT) Received: from ast-mbp ([2620:10d:c090:400::5:5929]) by smtp.gmail.com with ESMTPSA id f15sm785397pfd.215.2020.03.25.23.20.03 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 25 Mar 2020 23:20:04 -0700 (PDT) Date: Wed, 25 Mar 2020 23:20:01 -0700 From: Alexei Starovoitov To: John Fastabend Cc: ecree@solarflare.com, yhs@fb.com, daniel@iogearbox.net, netdev@vger.kernel.org, bpf@vger.kernel.org Subject: Re: [bpf-next PATCH 04/10] bpf: verifier, do explicit ALU32 bounds tracking Message-ID: <20200326062001.3j6yqyu7jne4gtfl@ast-mbp> References: <158507130343.15666.8018068546764556975.stgit@john-Precision-5820-Tower> <158507153582.15666.3091405867682349273.stgit@john-Precision-5820-Tower> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <158507153582.15666.3091405867682349273.stgit@john-Precision-5820-Tower> Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org 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 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. The rest is awesome.