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 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 3A684C433FE for ; Wed, 29 Sep 2021 11:20:39 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 22ACB613D0 for ; Wed, 29 Sep 2021 11:20:39 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S245698AbhI2LWS (ORCPT ); Wed, 29 Sep 2021 07:22:18 -0400 Received: from mx0a-001b2d01.pphosted.com ([148.163.156.1]:17600 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231261AbhI2LWF (ORCPT ); Wed, 29 Sep 2021 07:22:05 -0400 Received: from pps.filterd (m0098409.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.1.2/8.16.1.2) with SMTP id 18T9BfTU004513; Wed, 29 Sep 2021 07:19:55 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ibm.com; h=from : to : cc : subject : date : message-id : in-reply-to : references : mime-version : content-transfer-encoding; s=pp1; bh=+g8wp0I/DHpzgUrFDoHUxVuRI/eutiJXiCB45G6x38I=; b=r1aB7vwOZYybRexjIDEUwEv/8TAYbYNwtIxrKA8b3JpEX8Not6xFrdCvgGk6ewXL1SxD 6Nn3m5OLSYRFJUQ8vES3reoNrC90jYbsb0hFvMdiITZOk9oYt4JKO0lINN6SydnJ/Yp1 S1JudFd+CaNLTe0UCY16eRHVztnBSUIvfkbtZTtj9fAjb/IaCCe6t5sfiKp0r1IYZN8Z fpY47Ja0Sjm+UNdolUC4r2264kbTVefmNq3EPy10tsWF1ooCbSrbMTsONMAlkm3VcJWA 66bO8Y9WpfAOyJy7Wt+44Jy1HVZ3GXne/KoAkZAWb2uWDjz6nSLUmzzSZQzyb57Rw4DH lQ== Received: from pps.reinject (localhost [127.0.0.1]) by mx0a-001b2d01.pphosted.com with ESMTP id 3bcn9y2n6x-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Wed, 29 Sep 2021 07:19:54 -0400 Received: from m0098409.ppops.net (m0098409.ppops.net [127.0.0.1]) by pps.reinject (8.16.0.43/8.16.0.43) with SMTP id 18TAR9Bc018533; Wed, 29 Sep 2021 07:19:54 -0400 Received: from ppma06fra.de.ibm.com (48.49.7a9f.ip4.static.sl-reverse.com [159.122.73.72]) by mx0a-001b2d01.pphosted.com with ESMTP id 3bcn9y2n69-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Wed, 29 Sep 2021 07:19:54 -0400 Received: from pps.filterd (ppma06fra.de.ibm.com [127.0.0.1]) by ppma06fra.de.ibm.com (8.16.1.2/8.16.1.2) with SMTP id 18TBDLcu021974; Wed, 29 Sep 2021 11:19:51 GMT Received: from b06cxnps3074.portsmouth.uk.ibm.com (d06relay09.portsmouth.uk.ibm.com [9.149.109.194]) by ppma06fra.de.ibm.com with ESMTP id 3b9u1k58e7-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Wed, 29 Sep 2021 11:19:51 +0000 Received: from d06av24.portsmouth.uk.ibm.com (mk.ibm.com [9.149.105.60]) by b06cxnps3074.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id 18TBJlrH46006534 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Wed, 29 Sep 2021 11:19:47 GMT Received: from d06av24.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 6617842059; Wed, 29 Sep 2021 11:19:47 +0000 (GMT) Received: from d06av24.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id BAD8242074; Wed, 29 Sep 2021 11:19:42 +0000 (GMT) Received: from hbathini-workstation.ibm.com.com (unknown [9.43.83.199]) by d06av24.portsmouth.uk.ibm.com (Postfix) with ESMTP; Wed, 29 Sep 2021 11:19:42 +0000 (GMT) From: Hari Bathini To: naveen.n.rao@linux.ibm.com, christophe.leroy@csgroup.eu, mpe@ellerman.id.au, ast@kernel.org, daniel@iogearbox.net Cc: paulus@samba.org, andrii@kernel.org, kafai@fb.com, songliubraving@fb.com, yhs@fb.com, john.fastabend@gmail.com, kpsingh@kernel.org, netdev@vger.kernel.org, bpf@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, Hari Bathini Subject: [PATCH v4 8/8] bpf ppc32: Access only if addr is kernel address Date: Wed, 29 Sep 2021 16:48:55 +0530 Message-Id: <20210929111855.50254-9-hbathini@linux.ibm.com> X-Mailer: git-send-email 2.31.1 In-Reply-To: <20210929111855.50254-1-hbathini@linux.ibm.com> References: <20210929111855.50254-1-hbathini@linux.ibm.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-TM-AS-GCONF: 00 X-Proofpoint-GUID: 0r5rBPmu5aLXQxKkUK8bV1NpmjCe6INr X-Proofpoint-ORIG-GUID: pGdPj2uMhdqx_HZhWITf2bGg7EIsb0PY X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.182.1,Aquarius:18.0.790,Hydra:6.0.391,FMLib:17.0.607.475 definitions=2021-09-29_04,2021-09-29_01,2020-04-07_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 suspectscore=0 mlxscore=0 malwarescore=0 mlxlogscore=999 lowpriorityscore=0 spamscore=0 adultscore=0 bulkscore=0 clxscore=1015 impostorscore=0 phishscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2109230001 definitions=main-2109290068 Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org With KUAP enabled, any kernel code which wants to access userspace needs to be surrounded by disable-enable KUAP. But that is not happening for BPF_PROBE_MEM load instruction. Though PPC32 does not support read protection, considering the fact that PTR_TO_BTF_ID (which uses BPF_PROBE_MEM mode) could either be a valid kernel pointer or NULL but should never be a pointer to userspace address, execute BPF_PROBE_MEM load only if addr is kernel address, otherwise set dst_reg=0 and move on. This will catch NULL, valid or invalid userspace pointers. Only bad kernel pointer will be handled by BPF exception table. [Alexei suggested for x86] Suggested-by: Alexei Starovoitov Signed-off-by: Hari Bathini --- Changes in v4: * Adjusted the emit code to avoid using temporary reg. arch/powerpc/net/bpf_jit_comp32.c | 34 +++++++++++++++++++++++++++++++ 1 file changed, 34 insertions(+) diff --git a/arch/powerpc/net/bpf_jit_comp32.c b/arch/powerpc/net/bpf_jit_comp32.c index 6ee13a09c70d..2ac81563c78d 100644 --- a/arch/powerpc/net/bpf_jit_comp32.c +++ b/arch/powerpc/net/bpf_jit_comp32.c @@ -818,6 +818,40 @@ int bpf_jit_build_body(struct bpf_prog *fp, u32 *image, struct codegen_context * case BPF_LDX | BPF_PROBE_MEM | BPF_W: case BPF_LDX | BPF_MEM | BPF_DW: /* dst = *(u64 *)(ul) (src + off) */ case BPF_LDX | BPF_PROBE_MEM | BPF_DW: + /* + * As PTR_TO_BTF_ID that uses BPF_PROBE_MEM mode could either be a valid + * kernel pointer or NULL but not a userspace address, execute BPF_PROBE_MEM + * load only if addr is kernel address (see is_kernel_addr()), otherwise + * set dst_reg=0 and move on. + */ + if (BPF_MODE(code) == BPF_PROBE_MEM) { + PPC_LI32(_R0, TASK_SIZE - off); + EMIT(PPC_RAW_CMPLW(src_reg, _R0)); + PPC_BCC(COND_GT, (ctx->idx + 5) * 4); + EMIT(PPC_RAW_LI(dst_reg, 0)); + /* + * For BPF_DW case, "li reg_h,0" would be needed when + * !fp->aux->verifier_zext. Emit NOP otherwise. + * + * Note that "li reg_h,0" is emitted for BPF_B/H/W case, + * if necessary. So, jump there insted of emitting an + * additional "li reg_h,0" instruction. + */ + if (size == BPF_DW && !fp->aux->verifier_zext) + EMIT(PPC_RAW_LI(dst_reg_h, 0)); + else + EMIT(PPC_RAW_NOP()); + /* + * Need to jump two instructions instead of one for BPF_DW case + * as there are two load instructions for dst_reg_h & dst_reg + * respectively. + */ + if (size == BPF_DW) + PPC_JMP((ctx->idx + 3) * 4); + else + PPC_JMP((ctx->idx + 2) * 4); + } + switch (size) { case BPF_B: EMIT(PPC_RAW_LBZ(dst_reg, src_reg, off)); -- 2.31.1