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=-3.5 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS autolearn=no 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 0AB8BC2D0EF for ; Fri, 17 Apr 2020 18:17:30 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id C80AD206F9 for ; Fri, 17 Apr 2020 18:17:29 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="sWz2kV2w" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org C80AD206F9 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 3F0AF8E0041; Fri, 17 Apr 2020 14:17:29 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 3A1148E0023; Fri, 17 Apr 2020 14:17:29 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 2B7648E0041; Fri, 17 Apr 2020 14:17:29 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0034.hostedemail.com [216.40.44.34]) by kanga.kvack.org (Postfix) with ESMTP id 106E78E0023 for ; Fri, 17 Apr 2020 14:17:29 -0400 (EDT) Received: from smtpin15.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay01.hostedemail.com (Postfix) with ESMTP id C57C2180AE811 for ; Fri, 17 Apr 2020 18:17:28 +0000 (UTC) X-FDA: 76718154576.15.door31_414401932c752 X-HE-Tag: door31_414401932c752 X-Filterd-Recvd-Size: 4204 Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) by imf18.hostedemail.com (Postfix) with ESMTP for ; Fri, 17 Apr 2020 18:17:28 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20170209; h=In-Reply-To:Content-Type:MIME-Version :References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=vy45WYyAvnWC++4r2BeTmRg1PjZyiSd0b2OnG2cNJU4=; b=sWz2kV2wssYwweQnlTwBuJKzyR 7VUKhrbWXqHxSQj/1A0zpmh1Kqo3QLCka1o4544prwiy6c/4iHqUMzyGylYnt+McLHPs8lFc0/KpL hyIbBsAFXl6M0QCeXVxGYe5bPGGM8dg+ksbZyoZ+ydLz33z62TIdQqic2u3XvtzhXEJtO1cTsorjz sQPe/tkkyZEsFP757b455kygIg+AjxJSRfa+NbGYtL4e455Hu9kPaKsR4R9u5WmpmRav7TadG5cTF R1FweRHYUnu2ref+DlWyLZMyRGCveeIPeoUwv6K/TXltQHb6w67+NoaQ+dysV3SPmKrH2sx96sJgt tZbzUuXQ==; Received: from willy by bombadil.infradead.org with local (Exim 4.92.3 #3 (Red Hat Linux)) id 1jPVYE-0007Jp-SN; Fri, 17 Apr 2020 18:17:18 +0000 Date: Fri, 17 Apr 2020 11:17:18 -0700 From: Matthew Wilcox To: Christoph Hellwig Cc: Kees Cook , Iurii Zaikin , Luis Chamberlain , Greg Kroah-Hartman , "Rafael J. Wysocki" , Alexei Starovoitov , Daniel Borkmann , linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, netdev@vger.kernel.org, bpf@vger.kernel.org Subject: Re: [PATCH 6/6] sysctl: pass kernel pointers to ->proc_handler Message-ID: <20200417181718.GN5820@bombadil.infradead.org> References: <20200417064146.1086644-1-hch@lst.de> <20200417064146.1086644-7-hch@lst.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200417064146.1086644-7-hch@lst.de> 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 Fri, Apr 17, 2020 at 08:41:46AM +0200, Christoph Hellwig wrote: > diff --git a/fs/proc/proc_sysctl.c b/fs/proc/proc_sysctl.c > index b6f5d459b087..d5c9a9bf4e90 100644 > --- a/fs/proc/proc_sysctl.c > +++ b/fs/proc/proc_sysctl.c > @@ -539,13 +539,13 @@ static struct dentry *proc_sys_lookup(struct inode *dir, struct dentry *dentry, > return err; > } > > -static ssize_t proc_sys_call_handler(struct file *filp, void __user *buf, > +static ssize_t proc_sys_call_handler(struct file *filp, void __user *ubuf, > size_t count, loff_t *ppos, int write) > { > struct inode *inode = file_inode(filp); > struct ctl_table_header *head = grab_header(inode); > struct ctl_table *table = PROC_I(inode)->sysctl_entry; > - void *new_buf = NULL; > + void *kbuf; > ssize_t error; > > if (IS_ERR(head)) > @@ -564,27 +564,36 @@ static ssize_t proc_sys_call_handler(struct file *filp, void __user *buf, > if (!table->proc_handler) > goto out; > > - error = BPF_CGROUP_RUN_PROG_SYSCTL(head, table, write, buf, &count, > - ppos, &new_buf); > + if (write) { > + kbuf = memdup_user_nul(ubuf, count); > + if (IS_ERR(kbuf)) { > + error = PTR_ERR(kbuf); > + goto out; > + } > + } else { > + error = -ENOMEM; > + kbuf = kzalloc(count, GFP_KERNEL); > + if (!kbuf) > + goto out; > + } > + > + error = BPF_CGROUP_RUN_PROG_SYSCTL(head, table, write, &kbuf, &count, > + ppos); > if (error) > - goto out; > + goto out_free_buf; > > /* careful: calling conventions are nasty here */ I think this comment can go now ;-) > - if (new_buf) { > - mm_segment_t old_fs; > - > - old_fs = get_fs(); > - set_fs(KERNEL_DS); > - error = table->proc_handler(table, write, (void __user *)new_buf, > - &count, ppos); > - set_fs(old_fs); > - kfree(new_buf); > - } else { > - error = table->proc_handler(table, write, buf, &count, ppos); > - } > + error = table->proc_handler(table, write, kbuf, &count, ppos); > + if (error) > + goto out_free_buf; > + > + error = -EFAULT; > + if (copy_to_user(ubuf, kbuf, count)) > + goto out_free_buf; Can we skip this if !write? Indeed, don't we have to in case the user has passed a pointer to a read-only memory page?