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 X-Spam-Level: X-Spam-Status: No, score=-16.8 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 6AD1BC4320A for ; Mon, 26 Jul 2021 14:11:53 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id F1CD460F5A for ; Mon, 26 Jul 2021 14:11:52 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org F1CD460F5A Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=kvack.org Received: by kanga.kvack.org (Postfix) id 94FBA8D0003; Mon, 26 Jul 2021 10:11:52 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 8D7238D0002; Mon, 26 Jul 2021 10:11:52 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 7EBE38D0003; Mon, 26 Jul 2021 10:11:52 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0139.hostedemail.com [216.40.44.139]) by kanga.kvack.org (Postfix) with ESMTP id 635CD8D0002 for ; Mon, 26 Jul 2021 10:11:52 -0400 (EDT) Received: from smtpin10.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay04.hostedemail.com (Postfix) with ESMTP id 177D522883 for ; Mon, 26 Jul 2021 14:11:52 +0000 (UTC) X-FDA: 78404927664.10.04E951B Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by imf04.hostedemail.com (Postfix) with ESMTP id 96A9050000BB for ; Mon, 26 Jul 2021 14:11:51 +0000 (UTC) Received: by mail.kernel.org (Postfix) with ESMTPSA id 3FD1A60F55; Mon, 26 Jul 2021 14:11:49 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1627308711; bh=en+PAmlM0caG8kJ2VCv1dbeWPj0LXJV1wbRzu3p7AmQ=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=JC54lRSurzWqC72r0vaMWfndqofRq/mZ/p1HUHrNHldVfSI7yepI+BOFTrQgDVxWs i5G1nmc4x2hCZz7ufzcSHUzWZTuj9M6b2I5eyQHTByVNe9AYawmlafA/hJyGi7+RRk Sq7R/07wWvPCeakSLBAiNh8/+Iqmqg9w03wdDqBzogYHg0wbwxSZG6ZJFUS/b1ve6o JHtNN19vPYzbxyr02SfNNDJ9f6ZIRzpSTiVIph+tuo6qMpURr1DNf6pMmORnJhf4VM PaRpsbWoo/+zTeXIByNRzjTHTwu5IjZJ3bG3OH637j9sgfBIeWCqZa5vakwdDToR+J ZEa0dJ+ki/IrQ== From: Arnd Bergmann To: Russell King Cc: Arnd Bergmann , linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-arch@vger.kernel.org, linux-mm@kvack.org, Alexander Viro , Linus Walleij , Christoph Hellwig Subject: [PATCH v5 02/10] ARM: traps: use get_kernel_nofault instead of set_fs() Date: Mon, 26 Jul 2021 16:11:33 +0200 Message-Id: <20210726141141.2839385-3-arnd@kernel.org> X-Mailer: git-send-email 2.29.2 In-Reply-To: <20210726141141.2839385-1-arnd@kernel.org> References: <20210726141141.2839385-1-arnd@kernel.org> MIME-Version: 1.0 X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: 96A9050000BB Authentication-Results: imf04.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=JC54lRSu; dmarc=pass (policy=none) header.from=kernel.org; spf=pass (imf04.hostedemail.com: domain of arnd@kernel.org designates 198.145.29.99 as permitted sender) smtp.mailfrom=arnd@kernel.org X-Stat-Signature: 117ofdrkyyncizhundtuyknybx4xap3h X-HE-Tag: 1627308711-160664 Content-Transfer-Encoding: quoted-printable 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)=3D=3Dtrue is when the regs themselves are unreliable as a result of the condition that caused the trap. Reviewed-by: Christoph Hellwig Reviewed-by: Linus Walleij Signed-off-by: Arnd Bergmann --- 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 64308e3a5d0c..10dd3ef1f398 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 *st= r, unsigned long bottom, unsigned long top) { unsigned long first; - mm_segment_t fs; int i; =20 - /* - * 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 =3D get_fs(); - set_fs(KERNEL_DS); - printk("%s%s(0x%08lx to 0x%08lx)\n", lvl, str, bottom, top); =20 for (first =3D bottom & ~31; first < top; first +=3D 32) { @@ -145,7 +136,7 @@ static void dump_mem(const char *lvl, const char *str= , unsigned long bottom, for (p =3D first, i =3D 0; i < 8 && p < top; i++, p +=3D 4) { if (p >=3D bottom && p < top) { unsigned long val; - if (__get_user(val, (unsigned long *)p) =3D=3D 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 *st= r, unsigned long bottom, } printk("%s%04lx:%s\n", lvl, first & 0xffff, str); } - - set_fs(fs); } =20 -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 =3D instruction_pointer(regs); const int thumb =3D thumb_mode(regs); @@ -173,10 +162,20 @@ static void __dump_instr(const char *lvl, struct pt= _regs *regs) for (i =3D -4; i < 1 + !!thumb; i++) { unsigned int val, bad; =20 - if (thumb) - bad =3D get_user(val, &((u16 *)addr)[i]); - else - bad =3D get_user(val, &((u32 *)addr)[i]); + if (!user_mode(regs)) { + if (thumb) { + u16 val16; + bad =3D get_kernel_nofault(val16, &((u16 *)addr)[i]); + val =3D val16; + } else { + bad =3D get_kernel_nofault(val, &((u32 *)addr)[i]); + } + } else { + if (thumb) + bad =3D get_user(val, &((u16 *)addr)[i]); + else + bad =3D get_user(val, &((u32 *)addr)[i]); + } =20 if (!bad) p +=3D sprintf(p, i =3D=3D 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); } =20 -static void dump_instr(const char *lvl, struct pt_regs *regs) -{ - mm_segment_t fs; - - if (!user_mode(regs)) { - fs =3D 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_stru= ct *tsk, const char *loglvl) --=20 2.29.2