Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753995AbdHKWQF (ORCPT ); Fri, 11 Aug 2017 18:16:05 -0400 Received: from mail.linuxfoundation.org ([140.211.169.12]:33202 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753909AbdHKWBu (ORCPT ); Fri, 11 Aug 2017 18:01:50 -0400 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Daniel Borkmann , Michael Holzheu , "David S. Miller" Subject: [PATCH 4.12 06/17] bpf, s390: fix jit branch offset related to ldimm64 Date: Fri, 11 Aug 2017 15:01:25 -0700 Message-Id: <20170811220035.910493034@linuxfoundation.org> X-Mailer: git-send-email 2.14.0 In-Reply-To: <20170811220035.638197338@linuxfoundation.org> References: <20170811220035.638197338@linuxfoundation.org> User-Agent: quilt/0.65 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3598 Lines: 82 4.12-stable review patch. If anyone has any objections, please let me know. ------------------ From: Daniel Borkmann [ Upstream commit b0a0c2566f28e71e5e32121992ac8060cec75510 ] While testing some other work that required JIT modifications, I run into test_bpf causing a hang when JIT enabled on s390. The problematic test case was the one from ddc665a4bb4b (bpf, arm64: fix jit branch offset related to ldimm64), and turns out that we do have a similar issue on s390 as well. In bpf_jit_prog() we update next instruction address after returning from bpf_jit_insn() with an insn_count. bpf_jit_insn() returns either -1 in case of error (e.g. unsupported insn), 1 or 2. The latter is only the case for ldimm64 due to spanning 2 insns, however, next address is only set to i + 1 not taking actual insn_count into account, thus fix is to use insn_count instead of 1. bpf_jit_enable in mode 2 provides also disasm on s390: Before fix: 000003ff800349b6: a7f40003 brc 15,3ff800349bc ; target 000003ff800349ba: 0000 unknown 000003ff800349bc: e3b0f0700024 stg %r11,112(%r15) 000003ff800349c2: e3e0f0880024 stg %r14,136(%r15) 000003ff800349c8: 0db0 basr %r11,%r0 000003ff800349ca: c0ef00000000 llilf %r14,0 000003ff800349d0: e320b0360004 lg %r2,54(%r11) 000003ff800349d6: e330b03e0004 lg %r3,62(%r11) 000003ff800349dc: ec23ffeda065 clgrj %r2,%r3,10,3ff800349b6 ; jmp 000003ff800349e2: e3e0b0460004 lg %r14,70(%r11) 000003ff800349e8: e3e0b04e0004 lg %r14,78(%r11) 000003ff800349ee: b904002e lgr %r2,%r14 000003ff800349f2: e3b0f0700004 lg %r11,112(%r15) 000003ff800349f8: e3e0f0880004 lg %r14,136(%r15) 000003ff800349fe: 07fe bcr 15,%r14 After fix: 000003ff80ef3db4: a7f40003 brc 15,3ff80ef3dba 000003ff80ef3db8: 0000 unknown 000003ff80ef3dba: e3b0f0700024 stg %r11,112(%r15) 000003ff80ef3dc0: e3e0f0880024 stg %r14,136(%r15) 000003ff80ef3dc6: 0db0 basr %r11,%r0 000003ff80ef3dc8: c0ef00000000 llilf %r14,0 000003ff80ef3dce: e320b0360004 lg %r2,54(%r11) 000003ff80ef3dd4: e330b03e0004 lg %r3,62(%r11) 000003ff80ef3dda: ec230006a065 clgrj %r2,%r3,10,3ff80ef3de6 ; jmp 000003ff80ef3de0: e3e0b0460004 lg %r14,70(%r11) 000003ff80ef3de6: e3e0b04e0004 lg %r14,78(%r11) ; target 000003ff80ef3dec: b904002e lgr %r2,%r14 000003ff80ef3df0: e3b0f0700004 lg %r11,112(%r15) 000003ff80ef3df6: e3e0f0880004 lg %r14,136(%r15) 000003ff80ef3dfc: 07fe bcr 15,%r14 test_bpf.ko suite runs fine after the fix. Fixes: 054623105728 ("s390/bpf: Add s390x eBPF JIT compiler backend") Signed-off-by: Daniel Borkmann Tested-by: Michael Holzheu Signed-off-by: David S. Miller Signed-off-by: Greg Kroah-Hartman --- arch/s390/net/bpf_jit_comp.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) --- a/arch/s390/net/bpf_jit_comp.c +++ b/arch/s390/net/bpf_jit_comp.c @@ -1253,7 +1253,8 @@ static int bpf_jit_prog(struct bpf_jit * insn_count = bpf_jit_insn(jit, fp, i); if (insn_count < 0) return -1; - jit->addrs[i + 1] = jit->prg; /* Next instruction address */ + /* Next instruction address */ + jit->addrs[i + insn_count] = jit->prg; } bpf_jit_epilogue(jit);