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=-0.6 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,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 B3D91C83008 for ; Wed, 29 Apr 2020 11:27:03 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 7697620775 for ; Wed, 29 Apr 2020 11:27:03 +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="kg+m6tJ4" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 7697620775 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 E54CB8E0005; Wed, 29 Apr 2020 07:27:02 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id E051A8E0001; Wed, 29 Apr 2020 07:27:02 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id D41E48E0005; Wed, 29 Apr 2020 07:27:02 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0022.hostedemail.com [216.40.44.22]) by kanga.kvack.org (Postfix) with ESMTP id B8E648E0001 for ; Wed, 29 Apr 2020 07:27:02 -0400 (EDT) Received: from smtpin05.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay03.hostedemail.com (Postfix) with ESMTP id 57B678248047 for ; Wed, 29 Apr 2020 11:27:02 +0000 (UTC) X-FDA: 76760665884.05.seat99_5a84f455df947 X-HE-Tag: seat99_5a84f455df947 X-Filterd-Recvd-Size: 4058 Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) by imf05.hostedemail.com (Postfix) with ESMTP for ; Wed, 29 Apr 2020 11:27:01 +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=oMyZzcwYB9QX35xXWfMxn1LcoCBA2vSTd5XHHBAVDLs=; b=kg+m6tJ4HaLGqGi7L7gstSvKMs YDgkaZ/cGPu6ODEqaVw232Je5GEWjRRYEjHK9uOFWaUO4atRWg2BXWiI1LPIHTLBDFplziRU5H4ox iqBXcF7fqWs/xGGbdZMrsFfQNXONb0PeNewAdFs8D8C7gGh8Qd93dcCHhCOj9xSG9KhFSX9vBGFd7 2E0DlHpiVavu8Rp/hnJ+XjDqt7X64gadEpHZlb6llzDdzmw+boxgIp0pztPc8PbaNz1L9uC+SFjin DBqBBaU1br6h3UiT90ARqme+gdqd+rGPrBLkH0pIRMpRSLouPI9xpjg+OoOopTse/EsY+/3NFwI+E Mi8PEgcw==; Received: from hch by bombadil.infradead.org with local (Exim 4.92.3 #3 (Red Hat Linux)) id 1jTkrN-0008GQ-VZ; Wed, 29 Apr 2020 11:26:37 +0000 Date: Wed, 29 Apr 2020 04:26:37 -0700 From: Christoph Hellwig To: Luis Chamberlain Cc: axboe@kernel.dk, viro@zeniv.linux.org.uk, bvanassche@acm.org, gregkh@linuxfoundation.org, rostedt@goodmis.org, mingo@redhat.com, jack@suse.cz, ming.lei@redhat.com, nstange@suse.de, akpm@linux-foundation.org, mhocko@suse.com, yukuai3@huawei.com, linux-block@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Omar Sandoval , Hannes Reinecke , Michal Hocko , syzbot+603294af2d01acfdd6da@syzkaller.appspotmail.com Subject: Re: [PATCH v3 4/6] blktrace: fix debugfs use after free Message-ID: <20200429112637.GD21892@infradead.org> References: <20200429074627.5955-1-mcgrof@kernel.org> <20200429074627.5955-5-mcgrof@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200429074627.5955-5-mcgrof@kernel.org> X-SRS-Rewrite: SMTP reverse-path rewritten from by bombadil.infradead.org. See http://www.infradead.org/rpr.html 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: I can't say I'm a fan of all these long backtraces in commit logs.. > +static struct dentry *blk_debugfs_dir_register(const char *name) > +{ > + return debugfs_create_dir(name, blk_debugfs_root); > +} I don't think we really need this helper. > +void blk_part_debugfs_unregister(struct hd_struct *p) > +{ > + debugfs_remove_recursive(p->debugfs_dir); > + p->debugfs_dir = NULL; > +} Why do we need to clear the pointer here? > +#ifdef CONFIG_DEBUG_FS > + /* Currently only used by kernel/trace/blktrace.c */ > + struct dentry *debugfs_dir; > +#endif Does that comment really add value? > +static struct dentry *blk_trace_debugfs_dir(struct block_device *bdev, > + struct request_queue *q) > { > + struct hd_struct *p = NULL; > > + * Some drivers like scsi-generic use a NULL block device. For > + * other drivers when bdev != bdev->bd_contain we are doing a blktrace > + * on a parition, otherwise we know we are working on the whole > + * disk, and for that the request_queue already has its own debugfs_dir. > + * which we have been using for other things other than blktrace. > + */ > + if (bdev && bdev != bdev->bd_contains) > + p = bdev->bd_part; > > + if (p) > + return p->debugfs_dir; > + > + return q->debugfs_dir; This could be simplified down to: if (bdev && bdev != bdev->bd_contains) return bdev->bd_part->debugfs_dir; return q->debugfs_dir; Given that bd_part is in __blkdev_get very near bd_contains. Also given that this patch completely rewrites blk_trace_debugfs_dir is there any point in the previous patch? > @@ -491,6 +500,7 @@ static int do_blk_trace_setup(struct request_queue *q, char *name, dev_t dev, > struct dentry *dir = NULL; > int ret; > > + > if (!buts->buf_size || !buts->buf_nr) > return -EINVAL; > Spurious whitespace change.