From patchwork Mon Feb 11 05:25:01 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Tyler Hicks X-Patchwork-Id: 1039614 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Authentication-Results: ozlabs.org; spf=none (mailfrom) smtp.mailfrom=lists.ubuntu.com (client-ip=91.189.94.19; helo=huckleberry.canonical.com; envelope-from=kernel-team-bounces@lists.ubuntu.com; receiver=) Authentication-Results: ozlabs.org; dmarc=fail (p=none dis=none) header.from=canonical.com Received: from huckleberry.canonical.com (huckleberry.canonical.com [91.189.94.19]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ozlabs.org (Postfix) with ESMTPS id 43yZ4j2PyMz9sN6; Mon, 11 Feb 2019 16:25:40 +1100 (AEDT) Received: from localhost ([127.0.0.1] helo=huckleberry.canonical.com) by huckleberry.canonical.com with esmtp (Exim 4.86_2) (envelope-from ) id 1gt461-0003Y5-5q; Mon, 11 Feb 2019 05:25:33 +0000 Received: from youngberry.canonical.com ([91.189.89.112]) by huckleberry.canonical.com with esmtps (TLS1.0:DHE_RSA_AES_128_CBC_SHA1:128) (Exim 4.86_2) (envelope-from ) id 1gt45y-0003WJ-C1 for kernel-team@lists.ubuntu.com; Mon, 11 Feb 2019 05:25:30 +0000 Received: from 2.general.tyhicks.us.vpn ([10.172.64.53] helo=sec.ubuntu-ci) by youngberry.canonical.com with esmtpsa (TLS1.0:RSA_AES_128_CBC_SHA1:16) (Exim 4.76) (envelope-from ) id 1gt45x-0004w8-Lw; Mon, 11 Feb 2019 05:25:29 +0000 From: Tyler Hicks To: kernel-team@lists.ubuntu.com Subject: [PATCH 04/13] bpf: move tmp variable into ax register in interpreter Date: Mon, 11 Feb 2019 05:25:01 +0000 Message-Id: <1549862710-24224-5-git-send-email-tyhicks@canonical.com> X-Mailer: git-send-email 2.7.4 In-Reply-To: <1549862710-24224-1-git-send-email-tyhicks@canonical.com> References: <1549862710-24224-1-git-send-email-tyhicks@canonical.com> X-BeenThere: kernel-team@lists.ubuntu.com X-Mailman-Version: 2.1.20 Precedence: list List-Id: Kernel team discussions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , MIME-Version: 1.0 Errors-To: kernel-team-bounces@lists.ubuntu.com Sender: "kernel-team" From: Daniel Borkmann This change moves the on-stack 64 bit tmp variable in ___bpf_prog_run() into the hidden ax register. The latter is currently only used in JITs for constant blinding as a temporary scratch register, meaning the BPF interpreter will never see the use of ax. Therefore it is safe to use it for the cases where tmp has been used earlier. This is needed to later on allow restricted hidden use of ax in both interpreter and JITs. Signed-off-by: Daniel Borkmann Acked-by: Alexei Starovoitov Signed-off-by: Alexei Starovoitov CVE-2019-7308 (backported from commit 144cd91c4c2bced6eb8a7e25e590f6618a11e854) [tyhicks: Backport around context changes and missing commit 1ea47e01ad6e] Signed-off-by: Tyler Hicks --- include/linux/filter.h | 3 ++- kernel/bpf/core.c | 32 ++++++++++++++++---------------- 2 files changed, 18 insertions(+), 17 deletions(-) diff --git a/include/linux/filter.h b/include/linux/filter.h index e85292a16467..ec944f15f1a4 100644 --- a/include/linux/filter.h +++ b/include/linux/filter.h @@ -53,7 +53,8 @@ struct bpf_prog_aux; * constants. See JIT pre-step in bpf_jit_blind_constants(). */ #define BPF_REG_AX MAX_BPF_REG -#define MAX_BPF_JIT_REG (MAX_BPF_REG + 1) +#define MAX_BPF_EXT_REG (MAX_BPF_REG + 1) +#define MAX_BPF_JIT_REG MAX_BPF_EXT_REG /* unused opcode to mark special call to bpf_tail_call() helper */ #define BPF_TAIL_CALL 0xf0 diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c index 7949e8b8f94e..c8b57f2afbd6 100644 --- a/kernel/bpf/core.c +++ b/kernel/bpf/core.c @@ -51,6 +51,7 @@ #define DST regs[insn->dst_reg] #define SRC regs[insn->src_reg] #define FP regs[BPF_REG_FP] +#define AX regs[BPF_REG_AX] #define ARG1 regs[BPF_REG_ARG1] #define CTX regs[BPF_REG_CTX] #define IMM insn->imm @@ -778,7 +779,6 @@ EXPORT_SYMBOL_GPL(__bpf_call_base); static unsigned int ___bpf_prog_run(u64 *regs, const struct bpf_insn *insn, u64 *stack) { - u64 tmp; static const void *jumptable[256] = { [0 ... 255] = &&default_label, /* Now overwrite non-defaults ... */ @@ -952,22 +952,22 @@ static unsigned int ___bpf_prog_run(u64 *regs, const struct bpf_insn *insn, ALU64_MOD_X: if (unlikely(SRC == 0)) return 0; - div64_u64_rem(DST, SRC, &tmp); - DST = tmp; + div64_u64_rem(DST, SRC, &AX); + DST = AX; CONT; ALU_MOD_X: if (unlikely((u32)SRC == 0)) return 0; - tmp = (u32) DST; - DST = do_div(tmp, (u32) SRC); + AX = (u32) DST; + DST = do_div(AX, (u32) SRC); CONT; ALU64_MOD_K: - div64_u64_rem(DST, IMM, &tmp); - DST = tmp; + div64_u64_rem(DST, IMM, &AX); + DST = AX; CONT; ALU_MOD_K: - tmp = (u32) DST; - DST = do_div(tmp, (u32) IMM); + AX = (u32) DST; + DST = do_div(AX, (u32) IMM); CONT; ALU64_DIV_X: if (unlikely(SRC == 0)) @@ -977,17 +977,17 @@ static unsigned int ___bpf_prog_run(u64 *regs, const struct bpf_insn *insn, ALU_DIV_X: if (unlikely((u32)SRC == 0)) return 0; - tmp = (u32) DST; - do_div(tmp, (u32) SRC); - DST = (u32) tmp; + AX = (u32) DST; + do_div(AX, (u32) SRC); + DST = (u32) AX; CONT; ALU64_DIV_K: DST = div64_u64(DST, IMM); CONT; ALU_DIV_K: - tmp = (u32) DST; - do_div(tmp, (u32) IMM); - DST = (u32) tmp; + AX = (u32) DST; + do_div(AX, (u32) IMM); + DST = (u32) AX; CONT; ALU_END_TO_BE: switch (IMM) { @@ -1291,7 +1291,7 @@ STACK_FRAME_NON_STANDARD(___bpf_prog_run); /* jump table */ static unsigned int PROG_NAME(stack_size)(const void *ctx, const struct bpf_insn *insn) \ { \ u64 stack[stack_size / sizeof(u64)]; \ - u64 regs[MAX_BPF_REG]; \ + u64 regs[MAX_BPF_EXT_REG]; \ \ FP = (u64) (unsigned long) &stack[ARRAY_SIZE(stack)]; \ ARG1 = (u64) (unsigned long) ctx; \