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=-6.8 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=unavailable 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 605CDC3A59E for ; Wed, 21 Aug 2019 10:56:01 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 34F6422CF4 for ; Wed, 21 Aug 2019 10:56:01 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=netronome-com.20150623.gappssmtp.com header.i=@netronome-com.20150623.gappssmtp.com header.b="fHvjr7M6" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727168AbfHUK4A (ORCPT ); Wed, 21 Aug 2019 06:56:00 -0400 Received: from mail-wr1-f68.google.com ([209.85.221.68]:41256 "EHLO mail-wr1-f68.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727042AbfHUKz6 (ORCPT ); Wed, 21 Aug 2019 06:55:58 -0400 Received: by mail-wr1-f68.google.com with SMTP id j16so1579125wrr.8 for ; Wed, 21 Aug 2019 03:55:57 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=netronome-com.20150623.gappssmtp.com; s=20150623; h=references:user-agent:from:to:cc:subject:in-reply-to:date :message-id:mime-version; bh=WyMHZAA0Qc/+TYCGuweI620Z3fpFzwfapMrIB9ufTsg=; b=fHvjr7M6oaWkGoWvcj9pBZmawdN6AT/H7iPBdFn+TdXoKTZpAm6k6X457tR1nd17hx BWXvWHcu3QIwb6BXuuWalLFaUIArTyJ/Wn+8XazKdstH2/5ddO077ZNzX95OvfA/bLkF grtXXwefsLdQVmzT0uzIJAPKXWJ/t4NXvmjWvWSgzVv1hDNX2ywpxx7yX3l/98tgcLzX 3lfytGhqxQ4oJ2dCFhWF0gEoJ0E0cM4eROXmE6JK65SiDDRpJDp2ozvFrpDr/p+BpU1t bBIIuSD5SOjKDo7wg3besn6J0FWR+5wIvVjk/pprMgLOyEWk7wEaD0fuivujlrsHcBrP Tfjw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:references:user-agent:from:to:cc:subject :in-reply-to:date:message-id:mime-version; bh=WyMHZAA0Qc/+TYCGuweI620Z3fpFzwfapMrIB9ufTsg=; b=Q3UIrcmUYLCSVSF2w4miN83K626iFMVpW5hk+P9Jj37rQXU3rfNfso9xdoTnMP9p23 DxCAAU60GZg0JhBs5WQLocndLxlRSg1/ueKcUIu9l57zl1lmq/Sy5MDtNN8hu/tfqn07 m8NAAmcaDYJ6vZdZYKWAc09XeRjwtegpjJ5yqH5DCzOripSLIyWcC8E7IM3r4huR9F6D rzjnk3zjM8A2Rihze1KNHsKcZOcvBr9YysmLtWoc0/peeEdrlZThrtrz0w7VgFKXUiof lNyGQv7F57RntHZfAduLwBg5GKbv0w4vkz0ySblP5sTbLMRS/dkOdZdE59UDSMPUOCVU LeXw== X-Gm-Message-State: APjAAAWJPqw3q0GwGOESHbNdVZm6EV5I7KIzGMP927SrRQ4NucE7qOOF ufYQWKq/EVHWxRvioOGVjzvXcQiLVNc= X-Google-Smtp-Source: APXvYqxy71UJYE8nNVPrM78f/UonRomhIlrziR5U+ykFKDa0TRBkO8syiWp8ZwkpMnF9OvVCGS9LGg== X-Received: by 2002:a5d:4950:: with SMTP id r16mr39205612wrs.347.1566384956439; Wed, 21 Aug 2019 03:55:56 -0700 (PDT) Received: from LAPTOP-V3S7NLPL ([217.38.71.146]) by smtp.gmail.com with ESMTPSA id g65sm7099972wma.21.2019.08.21.03.55.55 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Wed, 21 Aug 2019 03:55:55 -0700 (PDT) References: <20190813171018.28221-1-naveen.n.rao@linux.vnet.ibm.com> <87d0gy6cj6.fsf@concordia.ellerman.id.au> User-agent: mu4e 0.9.18; emacs 25.2.2 From: Jiong Wang To: Michael Ellerman Cc: "Naveen N. Rao" , Alexei Starovoitov , Daniel Borkmann , Jiong Wang , bpf@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: Regression fix for bpf in v5.3 (was Re: [RFC PATCH] bpf: handle 32-bit zext during constant blinding) In-reply-to: <87d0gy6cj6.fsf@concordia.ellerman.id.au> Date: Wed, 21 Aug 2019 11:55:54 +0100 Message-ID: <87k1b6yeh1.fsf@netronome.com> MIME-Version: 1.0 Content-Type: text/plain Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Michael Ellerman writes: > "Naveen N. Rao" writes: >> Since BPF constant blinding is performed after the verifier pass, there >> are certain ALU32 instructions inserted which don't have a corresponding >> zext instruction inserted after. This is causing a kernel oops on >> powerpc and can be reproduced by running 'test_cgroup_storage' with >> bpf_jit_harden=2. >> >> Fix this by emitting BPF_ZEXT during constant blinding if >> prog->aux->verifier_zext is set. >> >> Fixes: a4b1d3c1ddf6cb ("bpf: verifier: insert zero extension according to analysis result") >> Reported-by: Michael Ellerman >> Signed-off-by: Naveen N. Rao >> --- >> This approach (the location where zext is being introduced below, in >> particular) works for powerpc, but I am not entirely sure if this is >> sufficient for other architectures as well. This is broken on v5.3-rc4. > > Any comment on this? Have commented on https://marc.info/?l=linux-netdev&m=156637836024743&w=2 The fix looks correct to me on "BPF_LD | BPF_IMM | BPF_DW", but looks unnecessary on two other places. It would be great if you or Naveen could confirm it. Thanks. Regards, Jiong > This is a regression in v5.3, which results in a kernel crash, it would > be nice to get it fixed before the release please? > > cheers > >> diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c >> index 8191a7db2777..d84146e6fd9e 100644 >> --- a/kernel/bpf/core.c >> +++ b/kernel/bpf/core.c >> @@ -890,7 +890,8 @@ int bpf_jit_get_func_addr(const struct bpf_prog *prog, >> >> static int bpf_jit_blind_insn(const struct bpf_insn *from, >> const struct bpf_insn *aux, >> - struct bpf_insn *to_buff) >> + struct bpf_insn *to_buff, >> + bool emit_zext) >> { >> struct bpf_insn *to = to_buff; >> u32 imm_rnd = get_random_int(); >> @@ -939,6 +940,8 @@ static int bpf_jit_blind_insn(const struct bpf_insn *from, >> *to++ = BPF_ALU32_IMM(BPF_MOV, BPF_REG_AX, imm_rnd ^ from->imm); >> *to++ = BPF_ALU32_IMM(BPF_XOR, BPF_REG_AX, imm_rnd); >> *to++ = BPF_ALU32_REG(from->code, from->dst_reg, BPF_REG_AX); >> + if (emit_zext) >> + *to++ = BPF_ZEXT_REG(from->dst_reg); >> break; >> >> case BPF_ALU64 | BPF_ADD | BPF_K: >> @@ -992,6 +995,10 @@ static int bpf_jit_blind_insn(const struct bpf_insn *from, >> off -= 2; >> *to++ = BPF_ALU32_IMM(BPF_MOV, BPF_REG_AX, imm_rnd ^ from->imm); >> *to++ = BPF_ALU32_IMM(BPF_XOR, BPF_REG_AX, imm_rnd); >> + if (emit_zext) { >> + *to++ = BPF_ZEXT_REG(BPF_REG_AX); >> + off--; >> + } >> *to++ = BPF_JMP32_REG(from->code, from->dst_reg, BPF_REG_AX, >> off); >> break; >> @@ -1005,6 +1012,8 @@ static int bpf_jit_blind_insn(const struct bpf_insn *from, >> case 0: /* Part 2 of BPF_LD | BPF_IMM | BPF_DW. */ >> *to++ = BPF_ALU32_IMM(BPF_MOV, BPF_REG_AX, imm_rnd ^ aux[0].imm); >> *to++ = BPF_ALU32_IMM(BPF_XOR, BPF_REG_AX, imm_rnd); >> + if (emit_zext) >> + *to++ = BPF_ZEXT_REG(BPF_REG_AX); >> *to++ = BPF_ALU64_REG(BPF_OR, aux[0].dst_reg, BPF_REG_AX); >> break; >> >> @@ -1088,7 +1097,8 @@ struct bpf_prog *bpf_jit_blind_constants(struct bpf_prog *prog) >> insn[1].code == 0) >> memcpy(aux, insn, sizeof(aux)); >> >> - rewritten = bpf_jit_blind_insn(insn, aux, insn_buff); >> + rewritten = bpf_jit_blind_insn(insn, aux, insn_buff, >> + clone->aux->verifier_zext); >> if (!rewritten) >> continue; >> >> -- >> 2.22.0