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=-19.4 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_GIT 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 785EEC43460 for ; Wed, 5 May 2021 12:12:38 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 449846121F for ; Wed, 5 May 2021 12:12:38 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232605AbhEEMNd (ORCPT ); Wed, 5 May 2021 08:13:33 -0400 Received: from mail.kernel.org ([198.145.29.99]:50558 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233763AbhEEMJ3 (ORCPT ); Wed, 5 May 2021 08:09:29 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id A1240613FB; Wed, 5 May 2021 12:08:12 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1620216493; bh=w+ksNPRAa0KVoiUtvaDFov4RY9DMF4suTFHZxsLavNA=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=zseHCLYpl3vfN73Ve7mHMq7HVEAE5JgK083pzPEiX/JjShSmM38mfQdFkueRbJmPH lmUVNHo+LE2aNhnOGPjimRxsBFuE6HVDb4qKL4jtfIyjiFQWtLgs1xjSz3xNLN1U/9 dX8taAwD3Wyp/pcPJ6yzj1a+TND8T6bYzdGmB74k= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Daniel Borkmann , Piotr Krysiuk , John Fastabend , Alexei Starovoitov Subject: [PATCH 5.12 05/17] bpf: Fix masking negation logic upon negative dst register Date: Wed, 5 May 2021 14:06:00 +0200 Message-Id: <20210505112325.126024016@linuxfoundation.org> X-Mailer: git-send-email 2.31.1 In-Reply-To: <20210505112324.956720416@linuxfoundation.org> References: <20210505112324.956720416@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Daniel Borkmann commit b9b34ddbe2076ade359cd5ce7537d5ed019e9807 upstream. The negation logic for the case where the off_reg is sitting in the dst register is not correct given then we cannot just invert the add to a sub or vice versa. As a fix, perform the final bitwise and-op unconditionally into AX from the off_reg, then move the pointer from the src to dst and finally use AX as the source for the original pointer arithmetic operation such that the inversion yields a correct result. The single non-AX mov in between is possible given constant blinding is retaining it as it's not an immediate based operation. Fixes: 979d63d50c0c ("bpf: prevent out of bounds speculation on pointer arithmetic") Signed-off-by: Daniel Borkmann Tested-by: Piotr Krysiuk Reviewed-by: Piotr Krysiuk Reviewed-by: John Fastabend Acked-by: Alexei Starovoitov Signed-off-by: Greg Kroah-Hartman --- kernel/bpf/verifier.c | 12 ++++-------- 1 file changed, 4 insertions(+), 8 deletions(-) --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -11760,14 +11760,10 @@ static int fixup_bpf_calls(struct bpf_ve *patch++ = BPF_ALU64_REG(BPF_OR, BPF_REG_AX, off_reg); *patch++ = BPF_ALU64_IMM(BPF_NEG, BPF_REG_AX, 0); *patch++ = BPF_ALU64_IMM(BPF_ARSH, BPF_REG_AX, 63); - if (issrc) { - *patch++ = BPF_ALU64_REG(BPF_AND, BPF_REG_AX, - off_reg); - insn->src_reg = BPF_REG_AX; - } else { - *patch++ = BPF_ALU64_REG(BPF_AND, off_reg, - BPF_REG_AX); - } + *patch++ = BPF_ALU64_REG(BPF_AND, BPF_REG_AX, off_reg); + if (!issrc) + *patch++ = BPF_MOV64_REG(insn->dst_reg, insn->src_reg); + insn->src_reg = BPF_REG_AX; if (isneg) insn->code = insn->code == code_add ? code_sub : code_add;