From nobody Mon Feb 9 15:10:35 2026 Received: from mx0a-0064b401.pphosted.com (mx0a-0064b401.pphosted.com [205.220.166.238]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id BCFA310F9; Sat, 26 Apr 2025 02:11:14 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=205.220.166.238 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1745633476; cv=none; b=VrinoPohedvQmi7k4AikrqgNoFMcKRCP35m5LUfsKzOKkkVkANAXFwgg7Sfl0zJmShTiaf1i6i607zz7/hZQmbbwSTnfGaiAn58O7MIcDgiB+2OYkwcmEEZ65joq5Inr+hC0vmi5/DqGJTpKBkCTfRhhAwTtjN/lVzAkSXzbYxU= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1745633476; c=relaxed/simple; bh=Jw7F1D6YkLAty219ZY+jebJe6PoKEARc/QsYTfjiD00=; h=From:To:CC:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=ttEk57CLxwf7TII+PcAEnWUKgko4lEAZq/gRikCpItu0EAsXgNX6jXLGo4gJ5fMF1CZKvDZaHANoVTcCN/UBXX8NwILOctkNB+7eW90PLdpaUkGHzaDpLuXEfxHodj1QMGmR5oRBGhlEdi30b+y9k1/tpnS7XfupzWfIuo37SG4= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=windriver.com; spf=pass smtp.mailfrom=windriver.com; arc=none smtp.client-ip=205.220.166.238 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=windriver.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=windriver.com Received: from pps.filterd (m0250810.ppops.net [127.0.0.1]) by mx0a-0064b401.pphosted.com (8.18.1.2/8.18.1.2) with ESMTP id 53Q2AT5i029409; Fri, 25 Apr 2025 19:11:00 -0700 Received: from ala-exchng02.corp.ad.wrs.com (ala-exchng02.wrs.com [147.11.82.254]) by mx0a-0064b401.pphosted.com (PPS) with ESMTPS id 466jhd4c3q-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128 verify=NOT); Fri, 25 Apr 2025 19:10:59 -0700 (PDT) Received: from ALA-EXCHNG02.corp.ad.wrs.com (147.11.82.254) by ALA-EXCHNG02.corp.ad.wrs.com (147.11.82.254) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2507.43; Fri, 25 Apr 2025 19:10:58 -0700 Received: from pek-lpd-ccm6.wrs.com (147.11.136.210) by ALA-EXCHNG02.corp.ad.wrs.com (147.11.82.254) with Microsoft SMTP Server id 15.1.2507.43 via Frontend Transport; Fri, 25 Apr 2025 19:10:56 -0700 From: Lizhi Xu To: CC: , , , , , , Subject: [PATCH V3] loop: Add sanity check for read/write_iter Date: Sat, 26 Apr 2025 10:10:55 +0800 Message-ID: <20250426021055.312912-1-lizhi.xu@windriver.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: References: Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Authority-Analysis: v=2.4 cv=ZNDXmW7b c=1 sm=1 tr=0 ts=680c40b3 cx=c_pps a=K4BcnWQioVPsTJd46EJO2w==:117 a=K4BcnWQioVPsTJd46EJO2w==:17 a=XR8D0OoHHMoA:10 a=edf1wS77AAAA:8 a=hSkVLCK3AAAA:8 a=t7CeM3EgAAAA:8 a=LV0KdC98gc1ixML1xO8A:9 a=DcSpbTIhAlouE1Uv7lRv:22 a=cQPPKAXgyycSBL8etih5:22 a=FdTzh2GWekK77mhwV6Dw:22 X-Proofpoint-ORIG-GUID: Z6NCK6Faewv0NcLTu7p9XuCbvFHNivMq X-Proofpoint-GUID: Z6NCK6Faewv0NcLTu7p9XuCbvFHNivMq X-Proofpoint-Spam-Details-Enc: AW1haW4tMjUwNDI2MDAxNCBTYWx0ZWRfX36t69HVb4iNb 9OGoam/8PVy0YAbU9RbN5ikQFtWiv9eMuDcBpD3Wqrw+NUiMr+97FfLXK+MJtju9the5iAiY1xF J9VcXPlL6UmehvZtK1Nz8jNCEswCofNvsKbRJ4a9XdX700PANxrJ5+LJfyM9kVWn1BgHLd1f8aC yGDQhLr3sa9oqcNqUfF9buapoWqLspHNqxR4Tz8g78BXH+urHI7Fkbgay2jMIQ6Ab0htQtKg0me gHlI8TtlKkkn9WKlBRq3tr/cRVR1J9LMJSh6zQrShc6y6RNwTt/yWWWtuLJx/orgDof0CwqVPFT ts6x7eHjeZ7xKwsDP2fTDAac89n391xoaWGNoB/7ZsbD6rHZ7GAZekyxURrdutVoVUtTtbDiCg2 Glg6lDbWUCucYRBmR7RLqlMWkmA9RqYaUkDyzq+90tECP3hwUEB/wF3Zibc3DrxplP0J2gij X-Sensitive_Customer_Information: Yes X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1099,Hydra:6.0.736,FMLib:17.12.80.40 definitions=2025-04-25_07,2025-04-24_02,2025-02-21_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 lowpriorityscore=0 priorityscore=1501 clxscore=1015 adultscore=0 spamscore=0 bulkscore=0 impostorscore=0 malwarescore=0 mlxlogscore=943 mlxscore=0 suspectscore=0 phishscore=0 classifier=spam authscore=0 authtc=n/a authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.21.0-2504070000 definitions=main-2504260014 Content-Type: text/plain; charset="utf-8" Some file systems do not support read_iter/write_iter, such as selinuxfs in this issue. So before calling them, first confirm that the interface is supported and then call it. Fixes: f2fed441c69b ("loop: stop using vfs_iter__{read,write} for buffered = I/O") Reported-by: syzbot+6af973a3b8dfd2faefdc@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=3D6af973a3b8dfd2faefdc Signed-off-by: Lizhi Xu --- V1 -> V2: move check to loop_configure and loop_change_fd V2 -> V3: using helper for this check drivers/block/loop.c | 22 ++++++++++++++++++++++ 1 file changed, 22 insertions(+) diff --git a/drivers/block/loop.c b/drivers/block/loop.c index 674527d770dc..7b78ddf7b819 100644 --- a/drivers/block/loop.c +++ b/drivers/block/loop.c @@ -582,6 +582,19 @@ static void loop_assign_backing_file(struct loop_devic= e *lo, struct file *file) lo->lo_min_dio_size =3D loop_query_min_dio_size(lo); } =20 +static int loop_check_backing_file(struct file *file, blk_mode_t mode, boo= l change) +{ + if (!file->f_op->read_iter) + return -EINVAL; + + if (((file->f_mode & FMODE_WRITE) || + (!change && (mode & BLK_OPEN_WRITE))) && + (!file->f_op->write_iter)) + return -EINVAL; + + return 0; +} + /* * loop_change_fd switched the backing store of a loopback device to * a new file. This is useful for operating system installers to free up @@ -603,6 +616,10 @@ static int loop_change_fd(struct loop_device *lo, stru= ct block_device *bdev, if (!file) return -EBADF; =20 + error =3D loop_check_backing_file(file, 0, true); + if (error) + return error; + /* suppress uevents while reconfiguring the device */ dev_set_uevent_suppress(disk_to_dev(lo->lo_disk), 1); =20 @@ -1039,6 +1056,11 @@ static int loop_configure(struct loop_device *lo, bl= k_mode_t mode, =20 if (!file) return -EBADF; + + error =3D loop_check_backing_file(file, mode, false); + if (error) + return error; + is_loop =3D is_loop_device(file); =20 /* This is safe, since we have a reference from open(). */ --=20 2.43.0