From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753766AbdK1Kax (ORCPT ); Tue, 28 Nov 2017 05:30:53 -0500 Received: from mail.linuxfoundation.org ([140.211.169.12]:58370 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753167AbdK1Kau (ORCPT ); Tue, 28 Nov 2017 05:30:50 -0500 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, John David Anglin , Helge Deller Subject: [PATCH 4.4 59/96] parisc: Fix validity check of pointer size argument in new CAS implementation Date: Tue, 28 Nov 2017 11:23:08 +0100 Message-Id: <20171128100506.690726719@linuxfoundation.org> X-Mailer: git-send-email 2.15.0 In-Reply-To: <20171128100503.067621614@linuxfoundation.org> References: <20171128100503.067621614@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 4.4-stable review patch. If anyone has any objections, please let me know. ------------------ From: John David Anglin commit 05f016d2ca7a4fab99d5d5472168506ddf95e74f upstream. As noted by Christoph Biedl, passing a pointer size of 4 in the new CAS implementation causes a kernel crash. The attached patch corrects the off by one error in the argument validity check. In reviewing the code, I noticed that we only perform word operations with the pointer size argument. The subi instruction intentionally uses a word condition on 64-bit kernels. Nullification was used instead of a cmpib instruction as the branch should never be taken. The shlw pseudo-operation generates a depw,z instruction and it clears the target before doing a shift left word deposit. Thus, we don't need to clip the upper 32 bits of this argument on 64-bit kernels. Tested with a gcc testsuite run with a 64-bit kernel. The gcc atomic code in libgcc is the only direct user of the new CAS implementation that I am aware of. Signed-off-by: John David Anglin Signed-off-by: Helge Deller Signed-off-by: Greg Kroah-Hartman --- arch/parisc/kernel/syscall.S | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) --- a/arch/parisc/kernel/syscall.S +++ b/arch/parisc/kernel/syscall.S @@ -688,15 +688,15 @@ cas_action: /* ELF32 Process entry path */ lws_compare_and_swap_2: #ifdef CONFIG_64BIT - /* Clip the input registers */ + /* Clip the input registers. We don't need to clip %r23 as we + only use it for word operations */ depdi 0, 31, 32, %r26 depdi 0, 31, 32, %r25 depdi 0, 31, 32, %r24 - depdi 0, 31, 32, %r23 #endif /* Check the validity of the size pointer */ - subi,>>= 4, %r23, %r0 + subi,>>= 3, %r23, %r0 b,n lws_exit_nosys /* Jump to the functions which will load the old and new values into