From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-lf1-f52.google.com (mail-lf1-f52.google.com [209.85.167.52]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 9E45F28E09 for ; Thu, 4 Jan 2024 18:30:50 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gmail.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="iNSISFVJ" Received: by mail-lf1-f52.google.com with SMTP id 2adb3069b0e04-50e9e5c97e1so941226e87.0 for ; Thu, 04 Jan 2024 10:30:50 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20230601; t=1704393049; x=1704997849; darn=vger.kernel.org; h=mime-version:user-agent:content-transfer-encoding:autocrypt :references:in-reply-to:date:cc:to:from:subject:message-id:from:to :cc:subject:date:message-id:reply-to; bh=3NbtTDNz1OO1Xy0CTFBMxkfIzdL78neCxWNMZ/LSgAU=; b=iNSISFVJrHJdX8kNgGhvx5pDs8w+7Se/dh+r0SVL9AvVCRlnTnvY59L5O5KkPjvf1e +8tyT0SmqFx/CeegZKCDyQ2CYkk4clN6F+koqGxbbqFWOWy7T1p5CCiZ6cjZ8Mfi9j2D Bzrtb0OmDTwiQSe+QC+jiYWjOmopeTeIn9XCYsQn88EYZ+IRkOdpQbhDSUw8VHPXGa13 klQRRL4+Th9fScuB3NhefAXQheWNEwh8NcoRoZrum4UiMO6Pb/o2WKa28PbVrdWzynvj xo4Hf/63IPEyindQBNuLuNrbMBqlLxIq5dT2gIhVc/21D9Drh4hxCJnJ8HuS+lGq2Tiq /3hg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1704393049; x=1704997849; h=mime-version:user-agent:content-transfer-encoding:autocrypt :references:in-reply-to:date:cc:to:from:subject:message-id :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=3NbtTDNz1OO1Xy0CTFBMxkfIzdL78neCxWNMZ/LSgAU=; b=PlUH03ZmjnkroB4rWfX3iAnyR9s4CFZMWUWs4sq40qXEPIJYivcyGCxbU7yUDoM5OF ELWmlvDg4Wgac14uuyuE3bz+8xhGQ1w03Q+ylyHKgGRArqLBFjMjCQxsTii2k2GN/C1E JZb5DzDqmJJlPunw6MwKYmMA3wUaZiqu4wRkn5iBywtZNR3gDMT9TWNuTFFYzA1ZAjs3 IJCk1y239X4zKRwL23A5Ja9nfM4mMdv/WJjC6VZYnQn/OphJaIY1b2HqJTUN2Z6WrI7t unN5Xszz/G8So/zcHfWS7DbtqoQidsc10KyRCQLim5bPCs0eZgvBRtzpqYP5NVB840Im mo2A== X-Gm-Message-State: AOJu0YzzpLFo2t5DoE14AmgeTNocQ5BaXtHQJ+xJHIMuY0rPwrcpzWl5 Z1QuI6FiMbGZhNgvFwCs65U= X-Google-Smtp-Source: AGHT+IGrq6vFiTrMClh+VEdl3JSksrxaDZVWIf5yHJEIdWhp4PVw88XmF9C7ZWtb9B4C/NnUBg1HgA== X-Received: by 2002:a05:6512:951:b0:50e:76aa:77d6 with SMTP id u17-20020a056512095100b0050e76aa77d6mr518273lft.32.1704393048580; Thu, 04 Jan 2024 10:30:48 -0800 (PST) Received: from [192.168.1.95] (host-176-36-0-241.b024.la.net.ua. [176.36.0.241]) by smtp.gmail.com with ESMTPSA id n2-20020a170906164200b00a269e651abesm14354325ejd.176.2024.01.04.10.30.47 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 04 Jan 2024 10:30:48 -0800 (PST) Message-ID: Subject: Re: [PATCH bpf-next v2 1/2] bpf: Track aligned st store as imprecise spilled registers From: Eduard Zingerman To: Yonghong Song , bpf@vger.kernel.org Cc: Alexei Starovoitov , Andrii Nakryiko , Daniel Borkmann , kernel-team@fb.com, Martin KaFai Lau , Kuniyuki Iwashima , Martin KaFai Lau Date: Thu, 04 Jan 2024 20:30:47 +0200 In-Reply-To: <20240103232617.3770727-1-yonghong.song@linux.dev> References: <20240103232617.3770727-1-yonghong.song@linux.dev> Autocrypt: addr=eddyz87@gmail.com; prefer-encrypt=mutual; keydata=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 nYzhLWGcczc6J71q1Dje0l5vIPaSFOgwmWD4DA+WvuxM/shH4rtWeodbv iCTce6yYIygHgUAtJcHozAlgRrL0jz44cggBTcoeXp/atckXK546OugZPnl00J3qmm5uWAznU6T5YDv2vCvAMEbz69ib+kHtnOSBvR0Jb86UZZqSb4ATfwMOWe9htGTjKMb0QQOLK0mTcrk/TtymaG+T4Fsos0kgrxqjgfrxxEhYcVNW8v8HISmFGFbqsJmFbVtgk68BcU0wgF8oFxo7u+XYQDdKbI1uQGNBGKNNQEBDADbQIdo8L3sdSWGQtu+LnFqCZoAbYurZCmUjLV3df1b+sg+GJZvVTmMZnzDP/ADufcbjopBBjGTRAY4L76T2niu2EpjclMMM3mtrOc738Kr3+RvPjUupdkZ1ZEZaWpf4cZm+4wH5GUfyu5pmD5WXX2i1r9XaUjeVtebvbuXWmWI1ZDTfOkiz/6Z0GDSeQeEqx2PXYBcepU7S9UNWttDtiZ0+IH4DZcvyKPUcK3tOj4u8GvO3RnOrglERzNCM/WhVdG1+vgU9fXO83TB/PcfAsvxYSie7u792s/I+yA4XKKh82PSTvTzg2/4vEDGpI9yubkfXRkQN28w+HKF5qoRB8/L1ZW/brlXkNzA6SveJhCnH7aOF0Yezl6TfX27w1CW5Xmvfi7X33V/SPvo0tY1THrO1c+bOjt5F+2/K3tvejmXMS/I6URwa8n1e767y5ErFKyXAYRweE9zarEgpNZTuSIGNNAqK+SiLLXt51G7P30TVavIeB6s2lCt1QKt62ccLqUAEQEAAYkBvAQYAQoAJhYhBMfui64wKUMqp1wmBC4MZXpJYEQJBQJijTUBAhsMBQkDwmcAAAoJEC4MZXpJYEQJkRAMAKNvWVwtXm/WxWoiLnXyF2WGXKoDe5+itTLvBmKcV/b1OKZF1s90V7WfSBz712eFAynEzyeezPbwU8QBiTpZcHXwQni3IYKvsh7s t1iq+gsfnXbPz5AnS598ScZI1oP7OrPSFJkt/z4acEbOQDQs8aUqrd46PV jsdqGvKnXZxzylux29UTNby4jTlz9pNJM+wPrDRmGfchLDUmf6CffaUYCbu4FiId+9+dcTCDvxbABRy1C3OJ8QY7cxfJ+pEZW18fRJ0XCl/fiV/ecAOfB3HsqgTzAn555h0rkFgay0hAvMU/mAW/CFNSIxV397zm749ZNLA0L2dMy1AKuOqH+/B+/ImBfJMDjmdyJQ8WU/OFRuGLdqOd2oZrA1iuPIa+yUYyZkaZfz/emQwpIL1+Q4p1R/OplA4yc301AqruXXUcVDbEB+joHW3hy5FwK5t5OwTKatrSJBkydSF9zdXy98fYzGniRyRA65P0Ix/8J3BYB4edY2/w0Ip/mdYsYQljBY0A== Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable User-Agent: Evolution 3.50.2 Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 On Wed, 2024-01-03 at 15:26 -0800, Yonghong Song wrote: I missed one thing while looking at this patch, please see below. [...] > diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c > index d4e31f61de0e..cfe7a68d90a5 100644 > --- a/kernel/bpf/verifier.c > +++ b/kernel/bpf/verifier.c > @@ -4491,7 +4491,7 @@ static int check_stack_write_fixed_off(struct bpf_v= erifier_env *env, > if (fls64(reg->umax_value) > BITS_PER_BYTE * size) > state->stack[spi].spilled_ptr.id =3D 0; > } else if (!reg && !(off % BPF_REG_SIZE) && is_bpf_st_mem(insn) && > - insn->imm !=3D 0 && env->bpf_capable) { > + env->bpf_capable) { > struct bpf_reg_state fake_reg =3D {}; > =20 > __mark_reg_known(&fake_reg, insn->imm); > @@ -4613,11 +4613,28 @@ static int check_stack_write_var_off(struct bpf_v= erifier_env *env, > =20 > /* Variable offset writes destroy any spilled pointers in range. */ > for (i =3D min_off; i < max_off; i++) { > + struct bpf_reg_state *spill_reg; > u8 new_type, *stype; > - int slot, spi; > + int slot, spi, j; > =20 > slot =3D -i - 1; > spi =3D slot / BPF_REG_SIZE; > + > + /* If writing_zero and the the spi slot contains a spill of value 0, > + * maintain the spill type. > + */ > + if (writing_zero && !(i % BPF_REG_SIZE) && is_spilled_scalar_reg(&stat= e->stack[spi])) { Talked to Andrii today, and he noted that spilled reg should be marked precise at this point. > + spill_reg =3D &state->stack[spi].spilled_ptr; > + if (tnum_is_const(spill_reg->var_off) && spill_reg->var_off.value =3D= =3D 0) { > + for (j =3D BPF_REG_SIZE; j > 0; j--) { > + if (state->stack[spi].slot_type[j - 1] !=3D STACK_SPILL) > + break; > + } > + i +=3D BPF_REG_SIZE - j - 1; > + continue; > + } > + } > + > stype =3D &state->stack[spi].slot_type[slot % BPF_REG_SIZE]; > mark_stack_slot_scratched(env, spi);