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=-6.8 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT autolearn=unavailable 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 AF8CEC4CED1 for ; Thu, 3 Oct 2019 17:28:26 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 87AD020830 for ; Thu, 3 Oct 2019 17:28:26 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1570123706; bh=tX/U8aujwjTxyRxka83R53J89nL+5YHZAjZBtNZPeIA=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=yVkSljot3Ma0z9R0M3tvnGavXP6iNnz2BZEEgIiPDcP6bTQlsOGtYyg6pUgxHVhtK H7FKd54rN6cfZzsOR3i2hBWWgfzwe8apEpWNva8hkjRprnMr1i18nsoFR0fzhW8Ykd mXzwTo7yvZmE/znYdo0wbF91gDFvLifU7UXa92sA= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2388428AbfJCQNt (ORCPT ); Thu, 3 Oct 2019 12:13:49 -0400 Received: from mail.kernel.org ([198.145.29.99]:36736 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1732701AbfJCQNt (ORCPT ); Thu, 3 Oct 2019 12:13:49 -0400 Received: from localhost (83-86-89-107.cable.dynamic.v4.ziggo.nl [83.86.89.107]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id A0FA420865; Thu, 3 Oct 2019 16:13:47 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1570119228; bh=tX/U8aujwjTxyRxka83R53J89nL+5YHZAjZBtNZPeIA=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=gIiuUvFwYP5FysDvbFus3RlqccsmidMdKnypAV3P215QjfimtZGcVbYPnQVBqhGyp nIBRe7lXAu7Lh7XUt5MBiexhN3+T+u64RP0ndQKjMWu2oyyWQjfBDCkaHmaQDEYTAI q23KezIlG2sBK1j4dUNJARD4TzZLiJg0lwpd9A0I= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Tetsuo Handa , syzbot Subject: [PATCH 4.14 174/185] /dev/mem: Bail out upon SIGKILL. Date: Thu, 3 Oct 2019 17:54:12 +0200 Message-Id: <20191003154520.113837237@linuxfoundation.org> X-Mailer: git-send-email 2.23.0 In-Reply-To: <20191003154437.541662648@linuxfoundation.org> References: <20191003154437.541662648@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: stable-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Tetsuo Handa commit 8619e5bdeee8b2c685d686281f2d2a6017c4bc15 upstream. syzbot found that a thread can stall for minutes inside read_mem() or write_mem() after that thread was killed by SIGKILL [1]. Reading from iomem areas of /dev/mem can be slow, depending on the hardware. While reading 2GB at one read() is legal, delaying termination of killed thread for minutes is bad. Thus, allow reading/writing /dev/mem and /dev/kmem to be preemptible and killable. [ 1335.912419][T20577] read_mem: sz=4096 count=2134565632 [ 1335.943194][T20577] read_mem: sz=4096 count=2134561536 [ 1335.978280][T20577] read_mem: sz=4096 count=2134557440 [ 1336.011147][T20577] read_mem: sz=4096 count=2134553344 [ 1336.041897][T20577] read_mem: sz=4096 count=2134549248 Theoretically, reading/writing /dev/mem and /dev/kmem can become "interruptible". But this patch chose "killable". Future patch will make them "interruptible" so that we can revert to "killable" if some program regressed. [1] https://syzkaller.appspot.com/bug?id=a0e3436829698d5824231251fad9d8e998f94f5e Signed-off-by: Tetsuo Handa Cc: stable Reported-by: syzbot Link: https://lore.kernel.org/r/1566825205-10703-1-git-send-email-penguin-kernel@I-love.SAKURA.ne.jp Signed-off-by: Greg Kroah-Hartman Signed-off-by: Greg Kroah-Hartman --- drivers/char/mem.c | 21 +++++++++++++++++++++ 1 file changed, 21 insertions(+) --- a/drivers/char/mem.c +++ b/drivers/char/mem.c @@ -97,6 +97,13 @@ void __weak unxlate_dev_mem_ptr(phys_add } #endif +static inline bool should_stop_iteration(void) +{ + if (need_resched()) + cond_resched(); + return fatal_signal_pending(current); +} + /* * This funcion reads the *physical* memory. The f_pos points directly to the * memory location. @@ -175,6 +182,8 @@ static ssize_t read_mem(struct file *fil p += sz; count -= sz; read += sz; + if (should_stop_iteration()) + break; } kfree(bounce); @@ -251,6 +260,8 @@ static ssize_t write_mem(struct file *fi p += sz; count -= sz; written += sz; + if (should_stop_iteration()) + break; } *ppos += written; @@ -464,6 +475,10 @@ static ssize_t read_kmem(struct file *fi read += sz; low_count -= sz; count -= sz; + if (should_stop_iteration()) { + count = 0; + break; + } } } @@ -488,6 +503,8 @@ static ssize_t read_kmem(struct file *fi buf += sz; read += sz; p += sz; + if (should_stop_iteration()) + break; } free_page((unsigned long)kbuf); } @@ -540,6 +557,8 @@ static ssize_t do_write_kmem(unsigned lo p += sz; count -= sz; written += sz; + if (should_stop_iteration()) + break; } *ppos += written; @@ -591,6 +610,8 @@ static ssize_t write_kmem(struct file *f buf += sz; virtr += sz; p += sz; + if (should_stop_iteration()) + break; } free_page((unsigned long)kbuf); }