From patchwork Fri Nov 5 09:30:22 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Baokun Li X-Patchwork-Id: 1551274 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Authentication-Results: bilbo.ozlabs.org; dkim=pass (2048-bit key; secure) header.d=lists.infradead.org header.i=@lists.infradead.org header.a=rsa-sha256 header.s=bombadil.20210309 header.b=QDfTXDlM; dkim-atps=neutral Authentication-Results: ozlabs.org; spf=none (no SPF record) smtp.mailfrom=lists.infradead.org (client-ip=2607:7c80:54:e::133; helo=bombadil.infradead.org; envelope-from=linux-mtd-bounces+incoming=patchwork.ozlabs.org@lists.infradead.org; receiver=) Received: from bombadil.infradead.org (bombadil.infradead.org [IPv6:2607:7c80:54:e::133]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) by bilbo.ozlabs.org (Postfix) with ESMTPS id 4Hlw1F17GCz9sXS for ; Fri, 5 Nov 2021 20:18:57 +1100 (AEDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:MIME-Version:Message-ID:Date:Subject:CC :To:From:Reply-To:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:In-Reply-To:References: List-Owner; bh=S/kFbT3wH6CYOtQdkae+yYbnclTNKHaRhr6w0Gc15jE=; b=QDfTXDlMeiwpEH HfQxoH86uN25Y/tFctEixJ9xM3Cglqb61uCD/uetSn8yjckZOb76Q5ip4ib5DMdcdW1QT5WgDfUF/ KUAj9jv9vPPGI+7qJupswoyqbeQOUS2A9VveJpqcUeO/kjyqYba9FFJQ8Ro57EwO01hBRZMfVYUfG gOvn6MG76QKqT1ZV2C5IHGRH0Pyx+jXuEW3Pw7NhVIsg2grmMx+5jlNTkRW4fUPkA7EI1rodpFISG ELYkgYWjGSMj94YgJbTanlHPDSSW2Oxy7GjLq9Ewq7vkoWCYkIBIMfzsWT4P6QQCEg3mbGett8DAC YD6K2nZqA3R/bnpnUMTw==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1mivMC-00Aw8G-Nq; Fri, 05 Nov 2021 09:17:56 +0000 Received: from szxga02-in.huawei.com ([45.249.212.188]) by bombadil.infradead.org with esmtps (Exim 4.94.2 #2 (Red Hat Linux)) id 1mivM8-00Aw5P-Rx for linux-mtd@lists.infradead.org; Fri, 05 Nov 2021 09:17:55 +0000 Received: from dggemv703-chm.china.huawei.com (unknown [172.30.72.54]) by szxga02-in.huawei.com (SkyGuard) with ESMTP id 4Hlvzb2fTPz90QY; Fri, 5 Nov 2021 17:17:31 +0800 (CST) Received: from dggpeml500020.china.huawei.com (7.185.36.88) by dggemv703-chm.china.huawei.com (10.3.19.46) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2308.15; Fri, 5 Nov 2021 17:17:42 +0800 Received: from huawei.com (10.175.127.227) by dggpeml500020.china.huawei.com (7.185.36.88) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2308.15; Fri, 5 Nov 2021 17:17:41 +0800 From: Baokun Li To: , , , , CC: , , Hulk Robot Subject: [PATCH -next V3] ubi: fix race condition between ctrl_cdev_ioctl and ubi_cdev_ioctl Date: Fri, 5 Nov 2021 17:30:22 +0800 Message-ID: <20211105093022.1360601-1-libaokun1@huawei.com> X-Mailer: git-send-email 2.31.1 MIME-Version: 1.0 X-Originating-IP: [10.175.127.227] X-ClientProxiedBy: dggems704-chm.china.huawei.com (10.3.19.181) To dggpeml500020.china.huawei.com (7.185.36.88) X-CFilter-Loop: Reflected X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20211105_021753_568016_7CB26CF2 X-CRM114-Status: GOOD ( 11.64 ) X-Spam-Score: -1.3 (-) X-Spam-Report: Spam detection software, running on the system "bombadil.infradead.org", has NOT identified this incoming email as spam. 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Content preview: Hulk Robot reported a KASAN report about use-after-free: ================================================================== BUG: KASAN: use-after-free in __list_del_entry_valid+0x13d/0x160 Read of siz [...] Content analysis details: (-1.3 points, 5.0 required) pts rule name description ---- ---------------------- -------------------------------------------------- -2.3 RCVD_IN_DNSWL_MED RBL: Sender listed at https://www.dnswl.org/, medium trust [45.249.212.188 listed in list.dnswl.org] -0.0 RCVD_IN_MSPIKE_H2 RBL: Average reputation (+2) [45.249.212.188 listed in wl.mailspike.net] -0.0 SPF_PASS SPF: sender matches SPF record 0.0 SPF_HELO_NONE SPF: HELO does not publish an SPF Record 1.0 HEXHASH_WORD Multiple instances of word + hexadecimal hash X-BeenThere: linux-mtd@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: Linux MTD discussion mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-mtd" Errors-To: linux-mtd-bounces+incoming=patchwork.ozlabs.org@lists.infradead.org Hulk Robot reported a KASAN report about use-after-free: ================================================================== BUG: KASAN: use-after-free in __list_del_entry_valid+0x13d/0x160 Read of size 8 at addr ffff888035e37d98 by task ubiattach/1385 [...] Call Trace: klist_dec_and_del+0xa7/0x4a0 klist_put+0xc7/0x1a0 device_del+0x4d4/0xed0 cdev_device_del+0x1a/0x80 ubi_attach_mtd_dev+0x2951/0x34b0 [ubi] ctrl_cdev_ioctl+0x286/0x2f0 [ubi] Allocated by task 1414: device_add+0x60a/0x18b0 cdev_device_add+0x103/0x170 ubi_create_volume+0x1118/0x1a10 [ubi] ubi_cdev_ioctl+0xb7f/0x1ba0 [ubi] Freed by task 1385: cdev_device_del+0x1a/0x80 ubi_remove_volume+0x438/0x6c0 [ubi] ubi_cdev_ioctl+0xbf4/0x1ba0 [ubi] [...] ================================================================== The lock held by ctrl_cdev_ioctl is ubi_devices_mutex, but the lock held by ubi_cdev_ioctl is ubi->device_mutex. Therefore, the two locks can be concurrent. ctrl_cdev_ioctl contains two operations: ubi_attach and ubi_detach. ubi_detach is bug-free because it uses reference counting to prevent concurrency. However, uif_init and uif_close in ubi_attach may race with ubi_cdev_ioctl. uif_init will race with ubi_cdev_ioctl as in the following stack. cpu1 cpu2 cpu3 _______________________|________________________|______________________ ctrl_cdev_ioctl ubi_attach_mtd_dev uif_init ubi_cdev_ioctl ubi_create_volume cdev_device_add ubi_add_volume // sysfs exist kill_volumes ubi_cdev_ioctl ubi_remove_volume cdev_device_del // first free ubi_free_volume cdev_del // double free cdev_device_del And uif_close will race with ubi_cdev_ioctl as in the following stack. cpu1 cpu2 cpu3 _______________________|________________________|______________________ ctrl_cdev_ioctl ubi_attach_mtd_dev uif_init ubi_cdev_ioctl ubi_create_volume cdev_device_add ubi_debugfs_init_dev //error goto out_uif; uif_close kill_volumes ubi_cdev_ioctl ubi_remove_volume cdev_device_del // first free ubi_free_volume // double free The cause of this problem is that commit 714fb87e8bc0 make device "available" before it becomes accessible via sysfs. Therefore, we roll back the modification. We will fix the race condition between ubi device creation and udev by removing ubi_get_device in vol_attribute_show and dev_attribute_show.This avoids accessing uninitialized ubi_devices[ubi_num]. ubi_get_device is used to prevent devices from being deleted during sysfs execution. However, now kernfs ensures that devices will not be deleted before all reference counting are released. The key process is shown in the following stack. device_del device_remove_attrs device_remove_groups sysfs_remove_groups sysfs_remove_group remove_files kernfs_remove_by_name kernfs_remove_by_name_ns __kernfs_remove kernfs_drain Fixes: 714fb87e8bc0 ("ubi: Fix race condition between ubi device creation and udev") Reported-by: Hulk Robot Signed-off-by: Baokun Li --- V1->V2: Add race in uif_close V2->V3: Solution modified becase ubi_add_volume might sleepping in spin_lock. drivers/mtd/ubi/build.c | 9 +-------- drivers/mtd/ubi/vmt.c | 8 +------- 2 files changed, 2 insertions(+), 15 deletions(-) diff --git a/drivers/mtd/ubi/build.c b/drivers/mtd/ubi/build.c index a7e3eb9befb6..a32050fecabf 100644 --- a/drivers/mtd/ubi/build.c +++ b/drivers/mtd/ubi/build.c @@ -351,9 +351,6 @@ static ssize_t dev_attribute_show(struct device *dev, * we still can use 'ubi->ubi_num'. */ ubi = container_of(dev, struct ubi_device, dev); - ubi = ubi_get_device(ubi->ubi_num); - if (!ubi) - return -ENODEV; if (attr == &dev_eraseblock_size) ret = sprintf(buf, "%d\n", ubi->leb_size); @@ -382,7 +379,6 @@ static ssize_t dev_attribute_show(struct device *dev, else ret = -EINVAL; - ubi_put_device(ubi); return ret; } @@ -979,9 +975,6 @@ int ubi_attach_mtd_dev(struct mtd_info *mtd, int ubi_num, goto out_detach; } - /* Make device "available" before it becomes accessible via sysfs */ - ubi_devices[ubi_num] = ubi; - err = uif_init(ubi); if (err) goto out_detach; @@ -1026,6 +1019,7 @@ int ubi_attach_mtd_dev(struct mtd_info *mtd, int ubi_num, wake_up_process(ubi->bgt_thread); spin_unlock(&ubi->wl_lock); + ubi_devices[ubi_num] = ubi; ubi_notify_all(ubi, UBI_VOLUME_ADDED, NULL); return ubi_num; @@ -1034,7 +1028,6 @@ int ubi_attach_mtd_dev(struct mtd_info *mtd, int ubi_num, out_uif: uif_close(ubi); out_detach: - ubi_devices[ubi_num] = NULL; ubi_wl_close(ubi); ubi_free_all_volumes(ubi); vfree(ubi->vtbl); diff --git a/drivers/mtd/ubi/vmt.c b/drivers/mtd/ubi/vmt.c index 139ee132bfbc..1bc7b3a05604 100644 --- a/drivers/mtd/ubi/vmt.c +++ b/drivers/mtd/ubi/vmt.c @@ -56,16 +56,11 @@ static ssize_t vol_attribute_show(struct device *dev, { int ret; struct ubi_volume *vol = container_of(dev, struct ubi_volume, dev); - struct ubi_device *ubi; - - ubi = ubi_get_device(vol->ubi->ubi_num); - if (!ubi) - return -ENODEV; + struct ubi_device *ubi = vol->ubi; spin_lock(&ubi->volumes_lock); if (!ubi->volumes[vol->vol_id]) { spin_unlock(&ubi->volumes_lock); - ubi_put_device(ubi); return -ENODEV; } /* Take a reference to prevent volume removal */ @@ -103,7 +98,6 @@ static ssize_t vol_attribute_show(struct device *dev, vol->ref_count -= 1; ubi_assert(vol->ref_count >= 0); spin_unlock(&ubi->volumes_lock); - ubi_put_device(ubi); return ret; }