From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Google-Smtp-Source: AB8JxZpabbYSQgmUKImX6vVqc9ZTmhS7EJwynrK1DiC606i02+dome8roIC3A4WmiLVOBKhOxvJ2 ARC-Seal: i=1; a=rsa-sha256; t=1524837851; cv=none; d=google.com; s=arc-20160816; b=ErU7QhMMVyJTI9sESOFfF6xRXGcaZCOP/h1K9KK5GhYB87pi4vBA5TD9gtrrqZSzkv GctNb7+qSaRZroUOadrjsKDoWeRFMHnJdVu7XuUuwOM3EAHFZ87svEu7Xe30xJjuutB2 dmu153K06QZNfpaIexDKHSA+hE8Far242xY4n4Q1amtVoUOVz6Q4eT5ooWSWnlHdANtQ YP33iDSpZuSk20nYKiK2hkNqEp7DqTOmv0w6yut+YI1lY+Os9Nh1aim8rDWoJ40cBPNx 98t2GRNiLjcUoknXKgFhCXJuhweeWG2KOnyrpoJaFLSYUHhD5fWieb8xn+WUIEsO6/C1 ISOw== 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=4f42l7bBK+po4LLPHUrlWUxqOCAtpc0IdmICZUXDSJc=; b=Ll/q26oUKRAeqfDGjvqYy4QTwfk+vVt2QXZoGKgoo23aYGPlBfqUnk04+zx1Y4EAA7 hg5zNCrBzV6cPk+U9WgqDnleL3HT8pGP5Wg/fKUwAzAjGGjY/5paTRDiDGwzYwaE8xKM zLybVPgKrPcLAkAVQ+ri+Nli0MZnDxhqEnRo3gAPcat8ia/LyFxD9sRIEQalPYd/S1ME ZXZMoWJ0oBE/qv2oKMWiBwqZsBeWYP8RF2PE0kkc3+P/s3w4MvhQv4W+MDxHH2LkMaxG QqvmdliDgKrnMyQ9fTNPU8H4jwnlynOhG6jTMX0Vf/wMahUrym+gqZ7C8bWPz0bSBFej X4xg== 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 239D92189D 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 , Farhan Ali , Christian Borntraeger Subject: [PATCH 4.9 40/74] s390/entry.S: fix spurious zeroing of r0 Date: Fri, 27 Apr 2018 15:58:30 +0200 Message-Id: <20180427135711.583204394@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?1598908181616624933?= X-GMAIL-MSGID: =?utf-8?q?1598908374715256524?= 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 From: Christian Borntraeger [ Upstream commit d3f468963cd6fd6d2aa5e26aed8b24232096d0e1 ] when a system call is interrupted we might call the critical section cleanup handler that re-does some of the operations. When we are between .Lsysc_vtime and .Lsysc_do_svc we might also redo the saving of the problem state registers r0-r7: .Lcleanup_system_call: [...] 0: # update accounting time stamp mvc __LC_LAST_UPDATE_TIMER(8),__LC_SYNC_ENTER_TIMER # set up saved register r11 lg %r15,__LC_KERNEL_STACK la %r9,STACK_FRAME_OVERHEAD(%r15) stg %r9,24(%r11) # r11 pt_regs pointer # fill pt_regs mvc __PT_R8(64,%r9),__LC_SAVE_AREA_SYNC ---> stmg %r0,%r7,__PT_R0(%r9) The problem is now, that we might have already zeroed out r0. The fix is to move the zeroing of r0 after sysc_do_svc. Reported-by: Farhan Ali Fixes: 7041d28115e91 ("s390: scrub registers on kernel entry and KVM exit") Signed-off-by: Christian Borntraeger Signed-off-by: Martin Schwidefsky Signed-off-by: Martin Schwidefsky Signed-off-by: Martin Schwidefsky Signed-off-by: Martin Schwidefsky Signed-off-by: Martin Schwidefsky Signed-off-by: Greg Kroah-Hartman --- arch/s390/kernel/entry.S | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) --- a/arch/s390/kernel/entry.S +++ b/arch/s390/kernel/entry.S @@ -434,13 +434,13 @@ ENTRY(system_call) UPDATE_VTIME %r10,%r13,__LC_SYNC_ENTER_TIMER BPENTER __TI_flags(%r12),_TIF_ISOLATE_BP stmg %r0,%r7,__PT_R0(%r11) - # clear user controlled register to prevent speculative use - xgr %r0,%r0 mvc __PT_R8(64,%r11),__LC_SAVE_AREA_SYNC mvc __PT_PSW(16,%r11),__LC_SVC_OLD_PSW mvc __PT_INT_CODE(4,%r11),__LC_SVC_ILC stg %r14,__PT_FLAGS(%r11) .Lsysc_do_svc: + # clear user controlled register to prevent speculative use + xgr %r0,%r0 lg %r10,__TI_sysc_table(%r12) # address of system call table llgh %r8,__PT_INT_CODE+2(%r11) slag %r8,%r8,2 # shift and test for svc 0