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 7FDA5C433EF for ; Wed, 29 Sep 2021 11:45:12 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 611196140F for ; Wed, 29 Sep 2021 11:45:12 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S244449AbhI2Lqw (ORCPT ); Wed, 29 Sep 2021 07:46:52 -0400 Received: from pegase2.c-s.fr ([93.17.235.10]:36967 "EHLO pegase2.c-s.fr" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229469AbhI2Lqv (ORCPT ); Wed, 29 Sep 2021 07:46:51 -0400 Received: from localhost (mailhub3.si.c-s.fr [172.26.127.67]) by localhost (Postfix) with ESMTP id 4HKF12091Jz9sYm; Wed, 29 Sep 2021 13:45:10 +0200 (CEST) X-Virus-Scanned: amavisd-new at c-s.fr Received: from pegase2.c-s.fr ([172.26.127.65]) by localhost (pegase2.c-s.fr [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id FmB_RmTJ4tn0; Wed, 29 Sep 2021 13:45:09 +0200 (CEST) Received: from messagerie.si.c-s.fr (messagerie.si.c-s.fr [192.168.25.192]) by pegase2.c-s.fr (Postfix) with ESMTP id 4HKF116GnTz9sYh; Wed, 29 Sep 2021 13:45:09 +0200 (CEST) Received: from localhost (localhost [127.0.0.1]) by messagerie.si.c-s.fr (Postfix) with ESMTP id BEC978B770; Wed, 29 Sep 2021 13:45:09 +0200 (CEST) X-Virus-Scanned: amavisd-new at c-s.fr Received: from messagerie.si.c-s.fr ([127.0.0.1]) by localhost (messagerie.si.c-s.fr [127.0.0.1]) (amavisd-new, port 10023) with ESMTP id uD7TAtbe3Oi8; Wed, 29 Sep 2021 13:45:09 +0200 (CEST) Received: from PO20335.IDSI0.si.c-s.fr (unknown [172.25.230.103]) by messagerie.si.c-s.fr (Postfix) with ESMTP id 2327A8B763; Wed, 29 Sep 2021 13:45:09 +0200 (CEST) Subject: Re: [PATCH v4 8/8] bpf ppc32: Access only if addr is kernel address To: Hari Bathini , naveen.n.rao@linux.ibm.com, 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 References: <20210929111855.50254-1-hbathini@linux.ibm.com> <20210929111855.50254-9-hbathini@linux.ibm.com> From: Christophe Leroy Message-ID: Date: Wed, 29 Sep 2021 13:45:08 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.11.0 MIME-Version: 1.0 In-Reply-To: <20210929111855.50254-9-hbathini@linux.ibm.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: fr-FR Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org Le 29/09/2021 à 13:18, Hari Bathini a écrit : > 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 Reviewed-by: Christophe Leroy > --- > > 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)); > 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 91716C433EF for ; Wed, 29 Sep 2021 11:46:23 +0000 (UTC) Received: from lists.ozlabs.org (lists.ozlabs.org [112.213.38.117]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id A800661407 for ; Wed, 29 Sep 2021 11:46:22 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org A800661407 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=csgroup.eu Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=lists.ozlabs.org Received: from boromir.ozlabs.org (localhost [IPv6:::1]) by lists.ozlabs.org (Postfix) with ESMTP id 4HKF2P2cXGz3cP0 for ; Wed, 29 Sep 2021 21:46:21 +1000 (AEST) Authentication-Results: lists.ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=csgroup.eu (client-ip=93.17.235.10; helo=pegase2.c-s.fr; envelope-from=christophe.leroy@csgroup.eu; receiver=) Received: from pegase2.c-s.fr (pegase2.c-s.fr [93.17.235.10]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 4HKF155nMwz3bhs for ; Wed, 29 Sep 2021 21:45:13 +1000 (AEST) Received: from localhost (mailhub3.si.c-s.fr [172.26.127.67]) by localhost (Postfix) with ESMTP id 4HKF12091Jz9sYm; Wed, 29 Sep 2021 13:45:10 +0200 (CEST) X-Virus-Scanned: amavisd-new at c-s.fr Received: from pegase2.c-s.fr ([172.26.127.65]) by localhost (pegase2.c-s.fr [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id FmB_RmTJ4tn0; Wed, 29 Sep 2021 13:45:09 +0200 (CEST) Received: from messagerie.si.c-s.fr (messagerie.si.c-s.fr [192.168.25.192]) by pegase2.c-s.fr (Postfix) with ESMTP id 4HKF116GnTz9sYh; Wed, 29 Sep 2021 13:45:09 +0200 (CEST) Received: from localhost (localhost [127.0.0.1]) by messagerie.si.c-s.fr (Postfix) with ESMTP id BEC978B770; Wed, 29 Sep 2021 13:45:09 +0200 (CEST) X-Virus-Scanned: amavisd-new at c-s.fr Received: from messagerie.si.c-s.fr ([127.0.0.1]) by localhost (messagerie.si.c-s.fr [127.0.0.1]) (amavisd-new, port 10023) with ESMTP id uD7TAtbe3Oi8; Wed, 29 Sep 2021 13:45:09 +0200 (CEST) Received: from PO20335.IDSI0.si.c-s.fr (unknown [172.25.230.103]) by messagerie.si.c-s.fr (Postfix) with ESMTP id 2327A8B763; Wed, 29 Sep 2021 13:45:09 +0200 (CEST) Subject: Re: [PATCH v4 8/8] bpf ppc32: Access only if addr is kernel address To: Hari Bathini , naveen.n.rao@linux.ibm.com, mpe@ellerman.id.au, ast@kernel.org, daniel@iogearbox.net References: <20210929111855.50254-1-hbathini@linux.ibm.com> <20210929111855.50254-9-hbathini@linux.ibm.com> From: Christophe Leroy Message-ID: Date: Wed, 29 Sep 2021 13:45:08 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.11.0 MIME-Version: 1.0 In-Reply-To: <20210929111855.50254-9-hbathini@linux.ibm.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: fr-FR Content-Transfer-Encoding: 8bit X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: songliubraving@fb.com, netdev@vger.kernel.org, john.fastabend@gmail.com, andrii@kernel.org, kpsingh@kernel.org, paulus@samba.org, yhs@fb.com, bpf@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, kafai@fb.com Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" Le 29/09/2021 à 13:18, Hari Bathini a écrit : > 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 Reviewed-by: Christophe Leroy > --- > > 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)); >