From mboxrd@z Thu Jan 1 00:00:00 1970 Received: with ECARTIS (v1.0.0; list linux-mips); Mon, 19 Mar 2018 19:14:45 +0100 (CET) Received: from mail.linuxfoundation.org ([140.211.169.12]:58972 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by eddie.linux-mips.org with ESMTP id S23992312AbeCSSOh5u82x (ORCPT ); Mon, 19 Mar 2018 19:14:37 +0100 Received: from localhost (LFbn-1-12247-202.w90-92.abo.wanadoo.fr [90.92.61.202]) by mail.linuxfoundation.org (Postfix) with ESMTPSA id 371E8F02; Mon, 19 Mar 2018 18:14:31 +0000 (UTC) From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, David Daney , James Hogan , Alexei Starovoitov , "Steven J. Hill" , linux-mips@linux-mips.org, netdev@vger.kernel.org, Ralf Baechle , Sasha Levin Subject: [PATCH 4.4 062/134] MIPS: BPF: Quit clobbering callee saved registers in JIT code. Date: Mon, 19 Mar 2018 19:05:45 +0100 Message-Id: <20180319171858.257403615@linuxfoundation.org> X-Mailer: git-send-email 2.16.2 In-Reply-To: <20180319171849.024066323@linuxfoundation.org> References: <20180319171849.024066323@linuxfoundation.org> User-Agent: quilt/0.65 X-stable: review MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Return-Path: X-Envelope-To: <"|/home/ecartis/ecartis -s linux-mips"> (uid 0) X-Orcpt: rfc822;linux-mips@linux-mips.org Original-Recipient: rfc822;linux-mips@linux-mips.org X-archive-position: 63056 X-ecartis-version: Ecartis v1.0.0 Sender: linux-mips-bounce@linux-mips.org Errors-to: linux-mips-bounce@linux-mips.org X-original-sender: gregkh@linuxfoundation.org Precedence: bulk List-help: List-unsubscribe: List-software: Ecartis version 1.0.0 List-Id: linux-mips X-List-ID: linux-mips List-subscribe: List-owner: List-post: List-archive: X-list: linux-mips 4.4-stable review patch. If anyone has any objections, please let me know. ------------------ From: David Daney [ Upstream commit 1ef0910cfd681f0bd0b81f8809935b2006e9cfb9 ] If bpf_needs_clear_a() returns true, only actually clear it if it is ever used. If it is not used, we don't save and restore it, so the clearing has the nasty side effect of clobbering caller state. Also, don't emit stack pointer adjustment instructions if the adjustment amount is zero. Signed-off-by: David Daney Cc: James Hogan Cc: Alexei Starovoitov Cc: Steven J. Hill Cc: linux-mips@linux-mips.org Cc: netdev@vger.kernel.org Cc: linux-kernel@vger.kernel.org Patchwork: https://patchwork.linux-mips.org/patch/15745/ Signed-off-by: Ralf Baechle Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman --- arch/mips/net/bpf_jit.c | 16 ++++++++++++---- 1 file changed, 12 insertions(+), 4 deletions(-) --- a/arch/mips/net/bpf_jit.c +++ b/arch/mips/net/bpf_jit.c @@ -527,7 +527,8 @@ static void save_bpf_jit_regs(struct jit u32 sflags, tmp_flags; /* Adjust the stack pointer */ - emit_stack_offset(-align_sp(offset), ctx); + if (offset) + emit_stack_offset(-align_sp(offset), ctx); tmp_flags = sflags = ctx->flags >> SEEN_SREG_SFT; /* sflags is essentially a bitmap */ @@ -579,7 +580,8 @@ static void restore_bpf_jit_regs(struct emit_load_stack_reg(r_ra, r_sp, real_off, ctx); /* Restore the sp and discard the scrach memory */ - emit_stack_offset(align_sp(offset), ctx); + if (offset) + emit_stack_offset(align_sp(offset), ctx); } static unsigned int get_stack_depth(struct jit_ctx *ctx) @@ -626,8 +628,14 @@ static void build_prologue(struct jit_ct if (ctx->flags & SEEN_X) emit_jit_reg_move(r_X, r_zero, ctx); - /* Do not leak kernel data to userspace */ - if (bpf_needs_clear_a(&ctx->skf->insns[0])) + /* + * Do not leak kernel data to userspace, we only need to clear + * r_A if it is ever used. In fact if it is never used, we + * will not save/restore it, so clearing it in this case would + * corrupt the state of the caller. + */ + if (bpf_needs_clear_a(&ctx->skf->insns[0]) && + (ctx->flags & SEEN_A)) emit_jit_reg_move(r_A, r_zero, ctx); }