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Violators will be prosecuted; (version=TLSv1/SSLv3 cipher=AES256-GCM-SHA384 bits=256/256) Sun, 28 Apr 2019 06:45:09 +0100 Received: from d06av26.portsmouth.uk.ibm.com (d06av26.portsmouth.uk.ibm.com [9.149.105.62]) by b06cxnps4074.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id x3S5j8gi45023464 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Sun, 28 Apr 2019 05:45:08 GMT Received: from d06av26.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id A9A88AE055; Sun, 28 Apr 2019 05:45:08 +0000 (GMT) Received: from d06av26.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 7F4C9AE056; Sun, 28 Apr 2019 05:45:07 +0000 (GMT) Received: from rapoport-lnx (unknown [9.148.8.112]) by d06av26.portsmouth.uk.ibm.com (Postfix) with ESMTPS; Sun, 28 Apr 2019 05:45:07 +0000 (GMT) Date: Sun, 28 Apr 2019 08:45:05 +0300 From: Mike Rapoport To: Peter Zijlstra Cc: linux-kernel@vger.kernel.org, Alexandre Chartre , Andy Lutomirski , Borislav Petkov , Dave Hansen , "H. Peter Anvin" , Ingo Molnar , James Bottomley , Jonathan Adams , Kees Cook , Paul Turner , Thomas Gleixner , linux-mm@kvack.org, linux-security-module@vger.kernel.org, x86@kernel.org Subject: Re: [RFC PATCH 2/7] x86/sci: add core implementation for system call isolation References: <1556228754-12996-1-git-send-email-rppt@linux.ibm.com> <1556228754-12996-3-git-send-email-rppt@linux.ibm.com> <20190426074956.GZ4038@hirez.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190426074956.GZ4038@hirez.programming.kicks-ass.net> User-Agent: Mutt/1.5.24 (2015-08-30) X-TM-AS-GCONF: 00 x-cbid: 19042805-0016-0000-0000-00000276086A X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 19042805-0017-0000-0000-000032D28A42 Message-Id: <20190428054505.GC14896@rapoport-lnx> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:,, definitions=2019-04-28_04:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 malwarescore=0 suspectscore=0 phishscore=0 bulkscore=0 spamscore=0 clxscore=1015 lowpriorityscore=0 mlxscore=0 impostorscore=0 mlxlogscore=475 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1810050000 definitions=main-1904280040 Sender: owner-linux-security-module@vger.kernel.org Precedence: bulk List-ID: On Fri, Apr 26, 2019 at 09:49:56AM +0200, Peter Zijlstra wrote: > On Fri, Apr 26, 2019 at 12:45:49AM +0300, Mike Rapoport wrote: > > The initial SCI implementation allows access to any kernel data, but it > > limits access to the code in the following way: > > * calls and jumps to known code symbols without offset are allowed > > * calls and jumps into a known symbol with offset are allowed only if that > > symbol was already accessed and the offset is in the next page > > * all other code access are blocked > > So if you have a large function and an in-function jump skips a page > you're toast. Right :( > Why not employ the instruction decoder we have and unconditionally allow > all direct JMP/CALL but verify indirect JMP/CALL and RET ? Apparently I didn't dig deep enough to find the instruction decoder :) Surely I can use it. > Anyway, I'm fearing the overhead of this one, this cannot be fast. Well, I think that the verification itself is not what will slow things down the most. IMHO, the major overhead is coming from cr3 switch. -- Sincerely yours, Mike.