From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 12629C433EF for ; Mon, 21 Feb 2022 15:23:15 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 5C1ED8D0002; Mon, 21 Feb 2022 10:23:15 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 571128D0001; Mon, 21 Feb 2022 10:23:15 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 3EA0B8D0002; Mon, 21 Feb 2022 10:23:15 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0175.hostedemail.com [216.40.44.175]) by kanga.kvack.org (Postfix) with ESMTP id 2C2658D0001 for ; Mon, 21 Feb 2022 10:23:15 -0500 (EST) Received: from smtpin20.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay05.hostedemail.com (Postfix) with ESMTP id B5CA7181FA8C5 for ; Mon, 21 Feb 2022 15:23:14 +0000 (UTC) X-FDA: 79167155508.20.CFCE9F1 Received: from elvis.franken.de (elvis.franken.de [193.175.24.41]) by imf29.hostedemail.com (Postfix) with ESMTP id DF4B112000B for ; Mon, 21 Feb 2022 15:23:13 +0000 (UTC) Received: from uucp (helo=alpha) by elvis.franken.de with local-bsmtp (Exim 3.36 #1) id 1nMAWk-00025w-00; Mon, 21 Feb 2022 16:23:02 +0100 Received: by alpha.franken.de (Postfix, from userid 1000) id 22D4EC25F8; Mon, 21 Feb 2022 16:21:30 +0100 (CET) Date: Mon, 21 Feb 2022 16:21:30 +0100 From: Thomas Bogendoerfer To: Arnd Bergmann Cc: Linus Torvalds , Christoph Hellwig , linux-arch , Linux-MM , Linux API , Arnd Bergmann , Linux Kernel Mailing List , Al Viro , Russell King - ARM Linux , Will Deacon , Guo Ren , Brian Cain , Geert Uytterhoeven , Michal Simek , Nick Hu , Greentime Hu , Dinh Nguyen , Stafford Horne , Helge Deller , Michael Ellerman , Peter Zijlstra , Ingo Molnar , Mark Rutland , Heiko Carstens , Rich Felker , David Miller , Richard Weinberger , the arch/x86 maintainers , Max Filippov , "Eric W . Biederman" , Andrew Morton , Ard Biesheuvel , alpha , "open list:SYNOPSYS ARC ARCHITECTURE" , linux-csky@vger.kernel.org, "open list:QUALCOMM HEXAGON..." , linux-ia64@vger.kernel.org, linux-m68k , "open list:BROADCOM NVRAM DRIVER" , Openrisc , Parisc List , linuxppc-dev , linux-riscv , linux-s390 , Linux-sh list , sparclinux , linux-um , "open list:TENSILICA XTENSA PORT (xtensa)" Subject: Re: [PATCH v2 09/18] mips: use simpler access_ok() Message-ID: <20220221152130.GA17373@alpha.franken.de> References: <20220216131332.1489939-1-arnd@kernel.org> <20220216131332.1489939-10-arnd@kernel.org> <20220221132456.GA7139@alpha.franken.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) Authentication-Results: imf29.hostedemail.com; dkim=none; spf=none (imf29.hostedemail.com: domain of tsbogend@alpha.franken.de has no SPF policy when checking 193.175.24.41) smtp.mailfrom=tsbogend@alpha.franken.de; dmarc=none X-Rspam-User: X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: DF4B112000B X-Stat-Signature: sx4xxez35c5wta8gw86gp86aoqinmnte X-HE-Tag: 1645456993-945699 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Mon, Feb 21, 2022 at 03:31:23PM +0100, Arnd Bergmann wrote: > On Mon, Feb 21, 2022 at 2:24 PM Thomas Bogendoerfer > wrote: > > On Wed, Feb 16, 2022 at 02:13:23PM +0100, Arnd Bergmann wrote: > > > > > > diff --git a/arch/mips/include/asm/uaccess.h b/arch/mips/include/asm/uaccess.h > > > index db9a8e002b62..d7c89dc3426c 100644 > > > > this doesn't work. For every access above maximum implemented virtual address > > space of the CPU an address error will be issued, but not a TLB miss. > > And address error isn't able to handle this situation. > > Ah, so the __ex_table entry only catches TLB misses? no, but there is no __ex_table handling in address error hanlder (yet). > Does this mean it also traps for kernel memory accesses, or do those > work again? it will trap for every access. > If the addresses on mips64 are separate like on > sparc64 or s390, the entire access_ok() step could be replaced > by a fixup code in the exception handler. I suppose this depends on > CONFIG_EVA and you still need a limit check at least when EVA is > disabled. only EVA has seperate address spaces for kernel/user. > > Is there a reason to not also #define TASK_SIZE_MAX __UA_LIMIT like > > for the 32bit case ? > > > > For 32-bit, the __UA_LIMIT is a compile-time constant, so the check > ends up being trivial. On all other architectures, the same thing can > be done after the set_fs removal, so I was hoping it would work here > as well. ic > I suspect doing the generic (size <= limit) && (addr <= (limit - size)) > check on mips64 with the runtime limit ends up slightly slower > than the current code that checks a bit mask instead. If you like, > I'll update it this way, otherwise I'd need help in form of a patch > that changes the exception handling so __get_user/__put_user > also return -EFAULT for an address error. that's what the patch does. For aligned accesses the patch should do the right thing, but it breaks unaligned get_user/put_user. Checking if the trapping vaddr is between end of CPU VM space and TASK_MAX_SIZE before exception handling should do the trick. I'll send a patch, if this works. Thomas. -- Crap can work. Given enough thrust pigs will fly, but it's not necessarily a good idea. [ RFC1925, 2.3 ]