From mboxrd@z Thu Jan 1 00:00:00 1970 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 66AD0200D8 for ; Thu, 9 Nov 2023 15:21:02 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="UXIQCzk6" Received: from mail-ej1-x629.google.com (mail-ej1-x629.google.com [IPv6:2a00:1450:4864:20::629]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C238C30E5 for ; Thu, 9 Nov 2023 07:21:01 -0800 (PST) Received: by mail-ej1-x629.google.com with SMTP id a640c23a62f3a-9dbb3d12aefso171964466b.0 for ; Thu, 09 Nov 2023 07:21:01 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20230601; t=1699543260; x=1700148060; 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=+x/PX+iK/7RFvN4QfswAeTVec4PLOOY/3WxBtPhxzy4=; b=UXIQCzk6a/J8S73E1wex+NI94m3+qf8LPdaHU7WcPntieO97s15Omdm1C3MmMFroxP 73ZkTH1W4tXhtTUFpko92e9Zz6nPY9cpoltglQoHUhrZCQH8GlOjW04bchGHrYVprOoo 3yIjUGiWfNDrdxGis4REm5EMkAb2SDiyZ5g8RinqtK9JpPGtWFnka3o9P/GXcOFUxUvp 8IjF3QTwxmG3SQrVqzrLNAqurW/HpG76JLeUOyaOBla+O3TpztpNlNURAvf/CFZQpOO8 jwwGPVFQY7GkCOeeiS4c1RaMgq4OgE7fAiSayl5l+/p7TEs88DI7LI88lOlZtQdXgWRC uMVw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1699543260; x=1700148060; 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=+x/PX+iK/7RFvN4QfswAeTVec4PLOOY/3WxBtPhxzy4=; b=nc5zMS3SLVwjeXqGUsVN8u5zflA2kCFlZJD0kNunPBGWnud/WDVdBWMm8scZHUX7z0 QR/wtA1FImnA9UuSlO+bJBj3rqBPwMaB21glQNUO2qmVa53JAoqAU0hBO/b+bzgCiDOX 0Rm9MWUqV/cF8k25/TJEnkcoi8/KJkIKAz8vKlEAK0azMmu/FD2T5KqSJYf1fybDHcbY D97xBh5BdJQ76A4RjJPxBIVmMw74+D0L9E8KNGDvR4nRQH/ygsBa18l9l6DY55QiVJQt x6vjAK17mOXLNDVKQfPxRACouP22YG4V/McARWqTO4y6XuGbQKxlbK1ho4Yw42boMZFT FhZQ== X-Gm-Message-State: AOJu0YxGcwJfcwZ/zkJQBxcm+JomNJ1dqlKvRJxh1rGLUPM8AFXVx+X1 kGBLZP6FBTNmUqfgQM/XMuM= X-Google-Smtp-Source: AGHT+IHhRrM2P6cVV0mYcaiqRaILF6woorSipg3wZLmC6xJWyne6NUmEojVr5qrx73gB7vs/NLZWbg== X-Received: by 2002:a17:907:26c4:b0:9dd:bd42:4ec7 with SMTP id bp4-20020a17090726c400b009ddbd424ec7mr4016627ejc.38.1699543260243; Thu, 09 Nov 2023 07:21:00 -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 f13-20020a170906c08d00b009b928eb8dd3sm2641447ejz.163.2023.11.09.07.20.59 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 09 Nov 2023 07:20:59 -0800 (PST) Message-ID: <891df9e42aee4ce7c46010cd93744e2b90819502.camel@gmail.com> Subject: Re: [PATCH bpf-next 6/7] bpf: preserve constant zero when doing partial register restore From: Eduard Zingerman To: Andrii Nakryiko , bpf@vger.kernel.org, ast@kernel.org, daniel@iogearbox.net, martin.lau@kernel.org Cc: kernel-team@meta.com Date: Thu, 09 Nov 2023 17:20:58 +0200 In-Reply-To: <20231031050324.1107444-7-andrii@kernel.org> References: <20231031050324.1107444-1-andrii@kernel.org> <20231031050324.1107444-7-andrii@kernel.org> Autocrypt: addr=eddyz87@gmail.com; prefer-encrypt=mutual; keydata=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 nYzhLWGcczc6J71q1Dje0l5vIPaSFOgwmWD4DA+WvuxM/shH4rtWeodbv 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 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 3.50.0 Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 On Mon, 2023-10-30 at 22:03 -0700, Andrii Nakryiko wrote: > Similar to special handling of STACK_ZERO, when reading 1/2/4 bytes from > stack from slot that has register spilled into it and that register has > a constant value zero, preserve that zero and mark spilled register as > precise for that. This makes spilled const zero register and STACK_ZERO > cases equivalent in their behavior. >=20 > Signed-off-by: Andrii Nakryiko Could you please add a test case? [...] > --- > kernel/bpf/verifier.c | 25 +++++++++++++++++++++---- > 1 file changed, 21 insertions(+), 4 deletions(-) >=20 > diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c > index 0eecc6b3109c..8cfe060e4938 100644 > --- a/kernel/bpf/verifier.c > +++ b/kernel/bpf/verifier.c > @@ -4958,22 +4958,39 @@ static int check_stack_read_fixed_off(struct bpf_= verifier_env *env, > copy_register_state(&state->regs[dst_regno], reg); > state->regs[dst_regno].subreg_def =3D subreg_def; > } else { [...] > + > + if (spill_cnt =3D=3D size && > + tnum_is_const(reg->var_off) && reg->var_off.value =3D=3D 0) { > + __mark_reg_const_zero(&state->regs[dst_regno]); > + /* this IS register fill, so keep insn_flags */ > + } else if (zero_cnt =3D=3D size) { > + /* similarly to mark_reg_stack_read(), preserve zeroes */ > + __mark_reg_const_zero(&state->regs[dst_regno]); > + insn_flags =3D 0; /* not restoring original register state */ > + } else { > + mark_reg_unknown(env, state->regs, dst_regno); > + insn_flags =3D 0; /* not restoring original register state */ > + } Condition for this branch is (off % BPF_REG_SIZE !=3D 0) || size !=3D spill= _size, is it necessary to check for some unusual offsets, e.g. off % BPF_REG_SIZE = =3D=3D 7 or something like that? [...]