From nobody Sat May 18 04:30:16 2024 Delivered-To: importer@patchew.org Authentication-Results: mx.zohomail.com; spf=pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) smtp.mailfrom=qemu-devel-bounces+importer=patchew.org@nongnu.org ARC-Seal: i=1; a=rsa-sha256; t=1620713089; cv=none; d=zohomail.com; s=zohoarc; b=Y3SxiJJAHDT/xij3WaXORomgvd9kr72drWbmHNODpi7q3LztUYQXybC+HVrb872WlNf3kOnE437nDquyzHZVHNx5BAdIj9AaQ+stXWAjWtQVRO3ekOEHgtQoKbwKyGYeztkZJzBWm51+cm+tuN9BBb7MH8JQ4DiGFWEWa6/lnW8= ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=zohomail.com; s=zohoarc; t=1620713089; h=Content-Type:Content-Transfer-Encoding:Cc:Date:From:List-Subscribe:List-Post:List-Id:List-Archive:List-Help:List-Unsubscribe:MIME-Version:Message-ID:Sender:Subject:To; bh=N7p4EIKjgk1OVxHuCy+NCZX5uXTxKitTczbaiClcKwk=; b=Ci5C5+zl+0hQw3ttlzh714n3SMHqv5Pbf55dGoTcurr49ldd2G4mALI/g8JeNq1JxPdPffnFLenO5xX+fdNJREGqxkvwTSLn5Reujc+keB05EkOsAtdCxX8NV+hUp9Ezj19R1FbpykSOeJgdrseZDIBwk/YPhTUPNXSjsa1RkEk= ARC-Authentication-Results: i=1; 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11 May 2021 13:55:50 +0800 Received: from G08CNEXMBPEKD04.g08.fujitsu.local (unknown [10.167.33.201]) by cn.fujitsu.com (Postfix) with ESMTP id 5E4734D0BA7A; Tue, 11 May 2021 13:55:49 +0800 (CST) Received: from G08CNEXCHPEKD08.g08.fujitsu.local (10.167.33.83) by G08CNEXMBPEKD04.g08.fujitsu.local (10.167.33.201) with Microsoft SMTP Server (TLS) id 15.0.1497.2; Tue, 11 May 2021 13:55:43 +0800 Received: from FNSTPC.g08.fujitsu.local (10.167.226.45) by G08CNEXCHPEKD08.g08.fujitsu.local (10.167.33.209) with Microsoft SMTP Server id 15.0.1497.2 via Frontend Transport; Tue, 11 May 2021 13:55:45 +0800 IronPort-HdrOrdr: =?us-ascii?q?A9a23=3ASMU+PK5N1yHmB7nhQQPXwPTXdLJyesId70hD?= =?us-ascii?q?6qkRc20wTiX8ra2TdZsguyMc9wx6ZJhNo7G90cq7MBbhHPxOkOos1N6ZNWGIhI?= =?us-ascii?q?LCFvAB0WKN+V3dMhy73utc+IMlSKJmFeD3ZGIQse/KpCW+DPYsqePqzJyV?= X-IronPort-AV: E=Sophos;i="5.82,290,1613404800"; d="scan'208";a="108115337" From: Li Zhijian To: , , , Subject: [PATCH v2] block: Improve backing file validation Date: Tue, 11 May 2021 13:55:18 +0800 Message-ID: <20210511055518.31876-1-lizhijian@cn.fujitsu.com> X-Mailer: git-send-email 2.30.2 MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable X-yoursite-MailScanner-ID: 5E4734D0BA7A.AE945 X-yoursite-MailScanner: Found to be clean X-yoursite-MailScanner-From: lizhijian@fujitsu.com Received-SPF: pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) client-ip=209.51.188.17; envelope-from=qemu-devel-bounces+importer=patchew.org@nongnu.org; helo=lists.gnu.org; Received-SPF: neutral client-ip=183.91.158.132; envelope-from=lizhijian@fujitsu.com; helo=heian.cn.fujitsu.com X-Spam_score_int: -33 X-Spam_score: -3.4 X-Spam_bar: --- X-Spam_report: (-3.4 / 5.0 requ) BAYES_00=-1.9, RCVD_IN_DNSWL_MED=-2.3, SPF_HELO_NONE=0.001, SPF_NEUTRAL=0.779 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: qemu-devel@nongnu.org, Li Zhijian Errors-To: qemu-devel-bounces+importer=patchew.org@nongnu.org Sender: "Qemu-devel" Image below user cases: case 1: ``` $ qemu-img create -f raw source.raw 1G $ qemu-img create -f qcow2 -F raw -b source.raw ./source.raw qemu-img info source.raw image: source.raw file format: qcow2 virtual size: 193K (197120 bytes) disk size: 196K cluster_size: 65536 backing file: source.raw <<<<<< backing file format: raw Format specific information: compat: 1.1 lazy refcounts: false refcount bits: 16 corrupt: false ``` case 2: ``` $ qemu-img create -f raw source.raw 1G $ ln -sf source.raw destination.qcow2 $ qemu-img create -f qcow2 -F raw -b source.raw ./destination.qcow2 qemu-img info source.raw image: source.raw file format: qcow2 <<<<<< virtual size: 2.0G (2147483648 bytes) disk size: 196K cluster_size: 65536 backing file: source.raw backing file format: raw Format specific information: compat: 1.1 lazy refcounts: false refcount bits: 16 corrupt: false ``` Generally, we don't expect to corrupte the source.raw anyway, while actually it does. Here we check their inode number instead of file name. Suggested-by: Daniel P. Berrang=C3=A9 Signed-off-by: Li Zhijian --- v2: utilize stat() instead of realpath() (Daniel) Signed-off-by: Li Zhijian --- block.c | 39 ++++++++++++++++++++++++++++++++------- 1 file changed, 32 insertions(+), 7 deletions(-) diff --git a/block.c b/block.c index 9ad725d205..db4ae57959 100644 --- a/block.c +++ b/block.c @@ -6431,6 +6431,37 @@ bool bdrv_op_blocker_is_empty(BlockDriverState *bs) return true; } =20 +static bool validate_backing_file(const char *filename, + const char *backing_file, Error **errp) +{ + struct stat filename_stat, backing_stat; + + if (backing_file[0] =3D=3D '\0') { + error_setg(errp, "Expected backing file name, got empty string"); + goto out; + } + + /* check whether filename and backing_file are refering to the same fi= le */ + if (stat(backing_file, &backing_stat) =3D=3D -1) { + error_setg(errp, "Cannot stat backing file %s", backing_file); + goto out; + } + if (stat(filename, &filename_stat) =3D=3D -1) { + /* Simply consider filename doesn't exist, no need to further chec= k */ + return true; + } + if ((filename_stat.st_dev =3D=3D backing_stat.st_dev) && + (filename_stat.st_ino =3D=3D backing_stat.st_ino)) { + error_setg(errp, "Error: Trying to create an image with the " + "same filename as the backing file"); + goto out; + } + + return true; +out: + return false; +} + void bdrv_img_create(const char *filename, const char *fmt, const char *base_filename, const char *base_fmt, char *options, uint64_t img_size, int flags, bool qui= et, @@ -6507,13 +6538,7 @@ void bdrv_img_create(const char *filename, const cha= r *fmt, =20 backing_file =3D qemu_opt_get(opts, BLOCK_OPT_BACKING_FILE); if (backing_file) { - if (!strcmp(filename, backing_file)) { - error_setg(errp, "Error: Trying to create an image with the " - "same filename as the backing file"); - goto out; - } - if (backing_file[0] =3D=3D '\0') { - error_setg(errp, "Expected backing file name, got empty string= "); + if (!validate_backing_file(filename, backing_file, errp)) { goto out; } } --=20 2.30.2