Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756418AbdLVOe1 (ORCPT ); Fri, 22 Dec 2017 09:34:27 -0500 Received: from mail-wm0-f66.google.com ([74.125.82.66]:33009 "EHLO mail-wm0-f66.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756048AbdLVObX (ORCPT ); Fri, 22 Dec 2017 09:31:23 -0500 X-Google-Smtp-Source: ACJfBovFLr59SYUTmfr2tIhA2FOh1dK6QVOmPBBE4lxausRebxvYNUX8rbI9iEZb6yoesdRvB+QlDA== From: Dongsu Park To: linux-kernel@vger.kernel.org Cc: containers@lists.linux-foundation.org, Alban Crequy , "Eric W . Biederman" , Miklos Szeredi , Seth Forshee , Sargun Dhillon , Dongsu Park , linux-mtd@lists.infradead.org Subject: [PATCH 02/11] mtd: Check permissions towards mtd block device inode when mounting Date: Fri, 22 Dec 2017 15:32:26 +0100 Message-Id: <945d325a2239efcd55273abb2bac41cfc7264fea.1512041070.git.dongsu@kinvolk.io> X-Mailer: git-send-email 2.13.6 In-Reply-To: References: Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1538 Lines: 45 From: Seth Forshee Unprivileged users should not be able to mount mtd block devices when they lack sufficient privileges towards the block device inode. Update mount_mtd() to validate that the user has the required access to the inode at the specified path. The check will be skipped for CAP_SYS_ADMIN, so privileged mounts will continue working as before. Patch v3 is available: https://patchwork.kernel.org/patch/7640011/ Cc: linux-mtd@lists.infradead.org Cc: linux-kernel@vger.kernel.org Signed-off-by: Seth Forshee Signed-off-by: Dongsu Park --- drivers/mtd/mtdsuper.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) diff --git a/drivers/mtd/mtdsuper.c b/drivers/mtd/mtdsuper.c index 4a4d40c0..3c8734f3 100644 --- a/drivers/mtd/mtdsuper.c +++ b/drivers/mtd/mtdsuper.c @@ -129,6 +129,7 @@ struct dentry *mount_mtd(struct file_system_type *fs_type, int flags, #ifdef CONFIG_BLOCK struct block_device *bdev; int ret, major; + int perm; #endif int mtdnr; @@ -180,7 +181,10 @@ struct dentry *mount_mtd(struct file_system_type *fs_type, int flags, /* try the old way - the hack where we allowed users to mount * /dev/mtdblock$(n) but didn't actually _use_ the blockdev */ - bdev = lookup_bdev(dev_name, 0); + perm = MAY_READ; + if (!(flags & MS_RDONLY)) + perm |= MAY_WRITE; + bdev = lookup_bdev(dev_name, perm); if (IS_ERR(bdev)) { ret = PTR_ERR(bdev); pr_debug("MTDSB: lookup_bdev() returned %d\n", ret); -- 2.13.6