From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Google-Smtp-Source: AB8JxZret0yknupqd2tMDmCb/Ew0oEkm9M4+7lV6QYEaPxK59DjWYxpvxjWKnzf57Pa2olgv/yT8 ARC-Seal: i=1; a=rsa-sha256; t=1524837848; cv=none; d=google.com; s=arc-20160816; b=A6fq245+5tqBbSA+r354EW0Ere2YfJKNLzZZJEJi4vaC/ANHDFKZXVkZYDwEURu36i 6hhojaIuAInkj4kruJTVw/fT+qIQwptK+oQP/ruvLM1PGjozyYogX5u0RzQZ+TsI+98m RUBhfzrEuC+khKlgqSp1f6W69KZunwLdUQxYlX0Yge0NP1ctK1tQv0VksJZP7fSH6jFj sTZdEUjqnRRxEeiib5aQL/2UBJQRahjF+N3l6JNLIBU6wz4F33XfzZ4RoJlGbu+p/Ox2 KuDjrywtarvYlF7OiQpceEPbDNaymQyy5q9yQsn7owPtHMxXbWlgq4h7SI8tKzicc6p7 zYKg== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=mime-version:user-agent:references:in-reply-to:message-id:date :subject:cc:to:from:dmarc-filter:arc-authentication-results; bh=4iVmRO6Aq5mi3UYQJ43xmeeLBAdEDpgw1/dtQ45aXBQ=; b=UGeomLCYKBiHR0R2Lvstx+yghNxlEFDlwOb11dvar3nE3gW6p4GZ/emwrnkMwKlgnr BzhtzCaV5IvVtHeV1z1O6+QqxLLZJu0lL/l1qC7sKMPYsq5WLaol41DhkDlWL1bnBB/I q+viCxHXAPfjVgDP03FCpb9loSBeQPWifNa4CDzEVsbNEGTZt7Ctw63lEUzON0vWjMfM k71/PrNwi0zJ9yIv+H6fCOYA8H3Uw0RAgMi3v7mwbtLvN4BkrKWrVLOiV76tLwwyx4my sCn03yZtS6oAHmTBV8/dp306WOXBL92RTzkN7/SgPbW7uaqZwjjy2adQ6GwAueSXHFBX tacw== ARC-Authentication-Results: i=1; mx.google.com; spf=pass (google.com: best guess record for domain of srs0=4/0d=hq=linuxfoundation.org=gregkh@kernel.org designates 198.145.29.99 as permitted sender) smtp.mailfrom=SRS0=4/0d=HQ=linuxfoundation.org=gregkh@kernel.org Authentication-Results: mx.google.com; spf=pass (google.com: best guess record for domain of srs0=4/0d=hq=linuxfoundation.org=gregkh@kernel.org designates 198.145.29.99 as permitted sender) smtp.mailfrom=SRS0=4/0d=HQ=linuxfoundation.org=gregkh@kernel.org DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 8AE9F21890 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=linuxfoundation.org Authentication-Results: mail.kernel.org; spf=fail smtp.mailfrom=gregkh@linuxfoundation.org From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Martin Schwidefsky Subject: [PATCH 4.9 39/74] s390: do not bypass BPENTER for interrupt system calls Date: Fri, 27 Apr 2018 15:58:29 +0200 Message-Id: <20180427135711.547413426@linuxfoundation.org> X-Mailer: git-send-email 2.17.0 In-Reply-To: <20180427135709.899303463@linuxfoundation.org> References: <20180427135709.899303463@linuxfoundation.org> User-Agent: quilt/0.65 X-stable: review MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-LABELS: =?utf-8?b?IlxcU2VudCI=?= X-GMAIL-THRID: =?utf-8?q?1598908178667353015?= X-GMAIL-MSGID: =?utf-8?q?1598908371871061958?= X-Mailing-List: linux-kernel@vger.kernel.org List-ID: 4.9-stable review patch. If anyone has any objections, please let me know. ------------------ From: Martin Schwidefsky [ Upstream commit d5feec04fe578c8dbd9e2e1439afc2f0af761ed4 ] The system call path can be interrupted before the switch back to the standard branch prediction with BPENTER has been done. The critical section cleanup code skips forward to .Lsysc_do_svc and bypasses the BPENTER. In this case the kernel and all subsequent code will run with the limited branch prediction. Fixes: eacf67eb9b32 ("s390: run user space and KVM guests with modified branch prediction") Signed-off-by: Martin Schwidefsky Signed-off-by: Greg Kroah-Hartman --- arch/s390/kernel/entry.S | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) --- a/arch/s390/kernel/entry.S +++ b/arch/s390/kernel/entry.S @@ -1316,7 +1316,8 @@ cleanup_critical: srag %r9,%r9,23 jz 0f mvc __TI_last_break(8,%r12),16(%r11) -0: # set up saved register r11 +0: BPENTER __TI_flags(%r12),_TIF_ISOLATE_BP + # set up saved register r11 lg %r15,__LC_KERNEL_STACK la %r9,STACK_FRAME_OVERHEAD(%r15) stg %r9,24(%r11) # r11 pt_regs pointer