From patchwork Fri Oct 30 15:49:12 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Arnd Bergmann X-Patchwork-Id: 11870143 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 9CBD5139F for ; Fri, 30 Oct 2020 15:49:36 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 3E66B22242 for ; Fri, 30 Oct 2020 15:49:36 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="TWyfwhH4" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 3E66B22242 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 465876B0074; Fri, 30 Oct 2020 11:49:35 -0400 (EDT) Delivered-To: linux-mm-outgoing@kvack.org Received: by kanga.kvack.org (Postfix, from userid 40) id 3ED9D6B0075; Fri, 30 Oct 2020 11:49:35 -0400 (EDT) X-Original-To: int-list-linux-mm@kvack.org X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 2B7186B0078; Fri, 30 Oct 2020 11:49:35 -0400 (EDT) X-Original-To: linux-mm@kvack.org X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0182.hostedemail.com [216.40.44.182]) by kanga.kvack.org (Postfix) with ESMTP id E52C66B0074 for ; Fri, 30 Oct 2020 11:49:34 -0400 (EDT) Received: from smtpin05.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay04.hostedemail.com (Postfix) with ESMTP id 8CC2D247F for ; Fri, 30 Oct 2020 15:49:34 +0000 (UTC) X-FDA: 77429026668.05.egg26_530151d27297 Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin05.hostedemail.com (Postfix) with ESMTP id 6DD69180199C6 for ; Fri, 30 Oct 2020 15:49:34 +0000 (UTC) X-Spam-Summary: 40,2.5,0,735379a34434e11b,d41d8cd98f00b204,arnd@kernel.org,,RULES_HIT:41:69:355:379:541:800:960:988:989:1260:1311:1314:1345:1359:1431:1437:1515:1535:1543:1711:1730:1747:1777:1792:2194:2199:2393:2559:2562:2693:2901:3138:3139:3140:3141:3142:3355:3865:3866:3867:3868:3870:3871:3872:3874:4321:5007:6119:6261:6653:7576:7904:9389:9592:10011:11026:11473:11658:11914:12043:12296:12297:12517:12519:12555:12679:12683:12895:13894:14181:14394:14721:21080:21433:21451:21627:21795:30012:30051:30054,0,RBL:198.145.29.99:@kernel.org:.lbl8.mailshell.net-62.2.0.100 64.100.201.201;04yfpfzuiypign6djcfbnd45u49oyoch5sy7ggadbf5sad4b8sqkguwijmaksma.879kkoju7t5bxjimk3ztqfb37q9buf9e3yqafoskobdc9d411hu45635gjf8gnk.c-lbl8.mailshell.net-223.238.255.100,CacheIP:none,Bayesian:0.5,0.5,0.5,Netcheck:none,DomainCache:0,MSF:not bulk,SPF:fp,MSBL:0,DNSBL:neutral,Custom_rules:0:1:0,LFtime:667,LUA_SUMMARY:none X-HE-Tag: egg26_530151d27297 X-Filterd-Recvd-Size: 5222 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by imf07.hostedemail.com (Postfix) with ESMTP for ; Fri, 30 Oct 2020 15:49:33 +0000 (UTC) Received: from localhost.localdomain (HSI-KBW-46-223-126-90.hsi.kabel-badenwuerttemberg.de [46.223.126.90]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 45B6C2151B; Fri, 30 Oct 2020 15:49:30 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1604072972; bh=ZWVfnKETIZSkSXx6wtt9uwQPqWB73y+8PUTcomvoy2w=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=TWyfwhH4qhKP35A1ntbbH2uTPQAKolFdHFHrtSWwJy5Sq5MvZ555anM/3vysGQt3y VQVFD3UKiR9sA0ZvC/Z2NGFLAwjkgRWm6gMwYLIrEkgPnGIiqou5iSFnPMElVNJU08 Q5LxJVIxJgvA6T5x1TmH6oh+G31HTu67VEszV24o= From: Arnd Bergmann To: Russell King , Christoph Hellwig Cc: linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-arch@vger.kernel.org, linux-mm@kvack.org, viro@zeniv.linux.org.uk, linus.walleij@linaro.org, arnd@arndb.de Subject: [PATCH 2/9] ARM: traps: use get_kernel_nofault instead of set_fs() Date: Fri, 30 Oct 2020 16:49:12 +0100 Message-Id: <20201030154919.1246645-2-arnd@kernel.org> X-Mailer: git-send-email 2.27.0 In-Reply-To: <20201030154919.1246645-1-arnd@kernel.org> References: <20201030154519.1245983-1-arnd@kernel.org> <20201030154919.1246645-1-arnd@kernel.org> MIME-Version: 1.0 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: From: Arnd Bergmann ARM uses set_fs() and __get_user() to allow the stack dumping code to access possibly invalid pointers carefully. These can be changed to the simpler get_kernel_nofault(), and allow the eventual removal of set_fs(). dump_instr() will print either kernel or user space pointers, depending on how it was called. For dump_mem(), I assume we are only interested in kernel pointers, and the only time that this is called with user_mode(regs)==true is when the regs themselves are unreliable as a result of the condition that caused the trap. Reviewed-by: Christoph Hellwig Signed-off-by: Arnd Bergmann Reviewed-by: Linus Walleij --- arch/arm/kernel/traps.c | 47 ++++++++++++++--------------------------- 1 file changed, 16 insertions(+), 31 deletions(-) diff --git a/arch/arm/kernel/traps.c b/arch/arm/kernel/traps.c index 17d5a785df28..c3964a283b63 100644 --- a/arch/arm/kernel/traps.c +++ b/arch/arm/kernel/traps.c @@ -122,17 +122,8 @@ static void dump_mem(const char *lvl, const char *str, unsigned long bottom, unsigned long top) { unsigned long first; - mm_segment_t fs; int i; - /* - * We need to switch to kernel mode so that we can use __get_user - * to safely read from kernel space. Note that we now dump the - * code first, just in case the backtrace kills us. - */ - fs = get_fs(); - set_fs(KERNEL_DS); - printk("%s%s(0x%08lx to 0x%08lx)\n", lvl, str, bottom, top); for (first = bottom & ~31; first < top; first += 32) { @@ -145,7 +136,7 @@ static void dump_mem(const char *lvl, const char *str, unsigned long bottom, for (p = first, i = 0; i < 8 && p < top; i++, p += 4) { if (p >= bottom && p < top) { unsigned long val; - if (__get_user(val, (unsigned long *)p) == 0) + if (get_kernel_nofault(val, (unsigned long *)p)) sprintf(str + i * 9, " %08lx", val); else sprintf(str + i * 9, " ????????"); @@ -153,11 +144,9 @@ static void dump_mem(const char *lvl, const char *str, unsigned long bottom, } printk("%s%04lx:%s\n", lvl, first & 0xffff, str); } - - set_fs(fs); } -static void __dump_instr(const char *lvl, struct pt_regs *regs) +static void dump_instr(const char *lvl, struct pt_regs *regs) { unsigned long addr = instruction_pointer(regs); const int thumb = thumb_mode(regs); @@ -173,10 +162,20 @@ static void __dump_instr(const char *lvl, struct pt_regs *regs) for (i = -4; i < 1 + !!thumb; i++) { unsigned int val, bad; - if (thumb) - bad = get_user(val, &((u16 *)addr)[i]); - else - bad = get_user(val, &((u32 *)addr)[i]); + if (!user_mode(regs)) { + if (thumb) { + u16 val16; + bad = get_kernel_nofault(val16, &((u16 *)addr)[i]); + val = val16; + } else { + bad = get_kernel_nofault(val, &((u32 *)addr)[i]); + } + } else { + if (thumb) + bad = get_user(val, &((u16 *)addr)[i]); + else + bad = get_user(val, &((u32 *)addr)[i]); + } if (!bad) p += sprintf(p, i == 0 ? "(%0*x) " : "%0*x ", @@ -189,20 +188,6 @@ static void __dump_instr(const char *lvl, struct pt_regs *regs) printk("%sCode: %s\n", lvl, str); } -static void dump_instr(const char *lvl, struct pt_regs *regs) -{ - mm_segment_t fs; - - if (!user_mode(regs)) { - fs = get_fs(); - set_fs(KERNEL_DS); - __dump_instr(lvl, regs); - set_fs(fs); - } else { - __dump_instr(lvl, regs); - } -} - #ifdef CONFIG_ARM_UNWIND static inline void dump_backtrace(struct pt_regs *regs, struct task_struct *tsk, const char *loglvl)