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 93389C433EF for ; Wed, 29 Sep 2021 11:20:33 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 7442B613CE for ; Wed, 29 Sep 2021 11:20:33 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S245610AbhI2LWL (ORCPT ); Wed, 29 Sep 2021 07:22:11 -0400 Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:56992 "EHLO mx0b-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S245699AbhI2LVw (ORCPT ); Wed, 29 Sep 2021 07:21:52 -0400 Received: from pps.filterd (m0098417.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.1.2/8.16.1.2) with SMTP id 18T9HOmm023048; Wed, 29 Sep 2021 07:19:43 -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=8uRYQgjx7hrdLFyt5Ht2DsP4CWx0pYcf5wH3eQKSHdE=; b=bEfD+TfrNy+wIcCyPgkLt5125wrf7ZJM1TS6fxUyRRzpbdiKEpFXVEFLKSQlx7Wi8rEd M2qEpycRebzZTgjWqRXcaNWI+klUst2uVectHbC2Bt2st3KkBYAbj2mBQMAyuNE9jPdQ GP+Rv+argjEQ3jmtq/iwYxTEraqegJXXo7NIDrgKpsQIzeYaNzbGGWJdtATAVBZDEuWQ wxolwkaGAjIzR1CQXuRVY3ERrKu2hJ0dBkCHn/L83q6s1HNmeDxI6d/CGm1t8O+oN27X tzQ94bnMoJiqEMWhiJt9qtbryeaIlDMKdgqLeyGSQuYOHtG19NFRDm3CfJozzTErbiZf +w== Received: from pps.reinject (localhost [127.0.0.1]) by mx0a-001b2d01.pphosted.com with ESMTP id 3bcmusk6um-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Wed, 29 Sep 2021 07:19:43 -0400 Received: from m0098417.ppops.net (m0098417.ppops.net [127.0.0.1]) by pps.reinject (8.16.0.43/8.16.0.43) with SMTP id 18TAcDsY005255; Wed, 29 Sep 2021 07:19:42 -0400 Received: from ppma02fra.de.ibm.com (47.49.7a9f.ip4.static.sl-reverse.com [159.122.73.71]) by mx0a-001b2d01.pphosted.com with ESMTP id 3bcmusk6tv-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Wed, 29 Sep 2021 07:19:42 -0400 Received: from pps.filterd (ppma02fra.de.ibm.com [127.0.0.1]) by ppma02fra.de.ibm.com (8.16.1.2/8.16.1.2) with SMTP id 18TBBw0g019748; Wed, 29 Sep 2021 11:19:40 GMT Received: from b06cxnps4076.portsmouth.uk.ibm.com (d06relay13.portsmouth.uk.ibm.com [9.149.109.198]) by ppma02fra.de.ibm.com with ESMTP id 3b9ud9n64m-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Wed, 29 Sep 2021 11:19:40 +0000 Received: from d06av24.portsmouth.uk.ibm.com (mk.ibm.com [9.149.105.60]) by b06cxnps4076.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id 18TBJbwv2687494 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Wed, 29 Sep 2021 11:19:37 GMT Received: from d06av24.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 3995342072; Wed, 29 Sep 2021 11:19:37 +0000 (GMT) Received: from d06av24.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 8022F4206C; Wed, 29 Sep 2021 11:19:32 +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 11:19:32 +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, Ravi Bangoria , Hari Bathini Subject: [PATCH v4 6/8] bpf ppc64: Access only if addr is kernel address Date: Wed, 29 Sep 2021 16:48:53 +0530 Message-Id: <20210929111855.50254-7-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: HMcK7K3ZJpocAL3f7AH4G8rchbuyyfnm X-Proofpoint-ORIG-GUID: 09EXvebg1u7dnPAWNDECri4yg36calLy 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 clxscore=1015 adultscore=0 spamscore=0 lowpriorityscore=0 phishscore=0 bulkscore=0 mlxscore=0 impostorscore=0 priorityscore=1501 mlxlogscore=999 suspectscore=0 malwarescore=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 From: Ravi Bangoria On PPC64 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. So, when BPF program tries to access invalid userspace address, page-fault handler considers it as bad KUAP fault: Kernel attempted to read user page (d0000000) - exploit attempt? (uid: 0) 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: Ravi Bangoria Signed-off-by: Hari Bathini --- Changes in v4: * Used IS_ENABLED() instead of #ifdef. * Dropped the else case that is not applicable for PPC64. arch/powerpc/net/bpf_jit_comp64.c | 26 ++++++++++++++++++++++++++ 1 file changed, 26 insertions(+) diff --git a/arch/powerpc/net/bpf_jit_comp64.c b/arch/powerpc/net/bpf_jit_comp64.c index 4170999371ee..e1ea64081ae1 100644 --- a/arch/powerpc/net/bpf_jit_comp64.c +++ b/arch/powerpc/net/bpf_jit_comp64.c @@ -727,6 +727,32 @@ int bpf_jit_build_body(struct bpf_prog *fp, u32 *image, struct codegen_context * /* dst = *(u64 *)(ul) (src + off) */ case BPF_LDX | BPF_MEM | BPF_DW: 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) { + EMIT(PPC_RAW_ADDI(b2p[TMP_REG_1], src_reg, off)); + if (IS_ENABLED(CONFIG_PPC_BOOK3E_64)) + PPC_LI64(b2p[TMP_REG_2], 0x8000000000000000ul); + else /* BOOK3S_64 */ + PPC_LI64(b2p[TMP_REG_2], PAGE_OFFSET); + EMIT(PPC_RAW_CMPLD(b2p[TMP_REG_1], b2p[TMP_REG_2])); + PPC_BCC(COND_GT, (ctx->idx + 4) * 4); + EMIT(PPC_RAW_LI(dst_reg, 0)); + /* + * Check if 'off' is word aligned because PPC_BPF_LL() + * (BPF_DW case) generates two instructions if 'off' is not + * word-aligned and one instruction otherwise. + */ + if (BPF_SIZE(code) == BPF_DW && (off & 3)) + 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