security/tomoyo/mount.c

0001 // SPDX-License-Identifier: GPL-2.0
0002 /*
0003  * security/tomoyo/mount.c
0004  *
0005  * Copyright (C) 2005-2011  NTT DATA CORPORATION
0006  */
0007
0008 #include <linux/slab.h>
0009 #include <uapi/linux/mount.h>
0010 #include "common.h"
0011
0012 /* String table for special mount operations. */
0013 static const char * const tomoyo_mounts[TOMOYO_MAX_SPECIAL_MOUNT] = {
0014     [TOMOYO_MOUNT_BIND]            = "--bind",
0015     [TOMOYO_MOUNT_MOVE]            = "--move",
0016     [TOMOYO_MOUNT_REMOUNT]         = "--remount",
0017     [TOMOYO_MOUNT_MAKE_UNBINDABLE] = "--make-unbindable",
0018     [TOMOYO_MOUNT_MAKE_PRIVATE]    = "--make-private",
0019     [TOMOYO_MOUNT_MAKE_SLAVE]      = "--make-slave",
0020     [TOMOYO_MOUNT_MAKE_SHARED]     = "--make-shared",
0021 };
0022
0023 /**
0024  * tomoyo_audit_mount_log - Audit mount log.
0025  *
0026  * @r: Pointer to "struct tomoyo_request_info".
0027  *
0028  * Returns 0 on success, negative value otherwise.
0029  */
0030 static int tomoyo_audit_mount_log(struct tomoyo_request_info *r)
0031 {
0032     return tomoyo_supervisor(r, "file mount %s %s %s 0x%lX\n",
0033                  r->param.mount.dev->name,
0034                  r->param.mount.dir->name,
0035                  r->param.mount.type->name,
0036                  r->param.mount.flags);
0037 }
0038
0039 /**
0040  * tomoyo_check_mount_acl - Check permission for path path path number operation.
0041  *
0042  * @r:   Pointer to "struct tomoyo_request_info".
0043  * @ptr: Pointer to "struct tomoyo_acl_info".
0044  *
0045  * Returns true if granted, false otherwise.
0046  */
0047 static bool tomoyo_check_mount_acl(struct tomoyo_request_info *r,
0048                    const struct tomoyo_acl_info *ptr)
0049 {
0050     const struct tomoyo_mount_acl *acl =
0051         container_of(ptr, typeof(*acl), head);
0052
0053     return tomoyo_compare_number_union(r->param.mount.flags,
0054                        &acl->flags) &&
0055         tomoyo_compare_name_union(r->param.mount.type,
0056                       &acl->fs_type) &&
0057         tomoyo_compare_name_union(r->param.mount.dir,
0058                       &acl->dir_name) &&
0059         (!r->param.mount.need_dev ||
0060          tomoyo_compare_name_union(r->param.mount.dev,
0061                        &acl->dev_name));
0062 }
0063
0064 /**
0065  * tomoyo_mount_acl - Check permission for mount() operation.
0066  *
0067  * @r:        Pointer to "struct tomoyo_request_info".
0068  * @dev_name: Name of device file. Maybe NULL.
0069  * @dir:      Pointer to "struct path".
0070  * @type:     Name of filesystem type.
0071  * @flags:    Mount options.
0072  *
0073  * Returns 0 on success, negative value otherwise.
0074  *
0075  * Caller holds tomoyo_read_lock().
0076  */
0077 static int tomoyo_mount_acl(struct tomoyo_request_info *r,
0078                 const char *dev_name,
0079                 const struct path *dir, const char *type,
0080                 unsigned long flags)
0081 {
0082     struct tomoyo_obj_info obj = { };
0083     struct path path;
0084     struct file_system_type *fstype = NULL;
0085     const char *requested_type = NULL;
0086     const char *requested_dir_name = NULL;
0087     const char *requested_dev_name = NULL;
0088     struct tomoyo_path_info rtype;
0089     struct tomoyo_path_info rdev;
0090     struct tomoyo_path_info rdir;
0091     int need_dev = 0;
0092     int error = -ENOMEM;
0093
0094     r->obj = &obj;
0095
0096     /* Get fstype. */
0097     requested_type = tomoyo_encode(type);
0098     if (!requested_type)
0099         goto out;
0100     rtype.name = requested_type;
0101     tomoyo_fill_path_info(&rtype);
0102
0103     /* Get mount point. */
0104     obj.path2 = *dir;
0105     requested_dir_name = tomoyo_realpath_from_path(dir);
0106     if (!requested_dir_name) {
0107         error = -ENOMEM;
0108         goto out;
0109     }
0110     rdir.name = requested_dir_name;
0111     tomoyo_fill_path_info(&rdir);
0112
0113     /* Compare fs name. */
0114     if (type == tomoyo_mounts[TOMOYO_MOUNT_REMOUNT]) {
0115         /* dev_name is ignored. */
0116     } else if (type == tomoyo_mounts[TOMOYO_MOUNT_MAKE_UNBINDABLE] ||
0117            type == tomoyo_mounts[TOMOYO_MOUNT_MAKE_PRIVATE] ||
0118            type == tomoyo_mounts[TOMOYO_MOUNT_MAKE_SLAVE] ||
0119            type == tomoyo_mounts[TOMOYO_MOUNT_MAKE_SHARED]) {
0120         /* dev_name is ignored. */
0121     } else if (type == tomoyo_mounts[TOMOYO_MOUNT_BIND] ||
0122            type == tomoyo_mounts[TOMOYO_MOUNT_MOVE]) {
0123         need_dev = -1; /* dev_name is a directory */
0124     } else {
0125         fstype = get_fs_type(type);
0126         if (!fstype) {
0127             error = -ENODEV;
0128             goto out;
0129         }
0130         if (fstype->fs_flags & FS_REQUIRES_DEV)
0131             /* dev_name is a block device file. */
0132             need_dev = 1;
0133     }
0134     if (need_dev) {
0135         /* Get mount point or device file. */
0136         if (!dev_name || kern_path(dev_name, LOOKUP_FOLLOW, &path)) {
0137             error = -ENOENT;
0138             goto out;
0139         }
0140         obj.path1 = path;
0141         requested_dev_name = tomoyo_realpath_from_path(&path);
0142         if (!requested_dev_name) {
0143             error = -ENOENT;
0144             goto out;
0145         }
0146     } else {
0147         /* Map dev_name to "<NULL>" if no dev_name given. */
0148         if (!dev_name)
0149             dev_name = "<NULL>";
0150         requested_dev_name = tomoyo_encode(dev_name);
0151         if (!requested_dev_name) {
0152             error = -ENOMEM;
0153             goto out;
0154         }
0155     }
0156     rdev.name = requested_dev_name;
0157     tomoyo_fill_path_info(&rdev);
0158     r->param_type = TOMOYO_TYPE_MOUNT_ACL;
0159     r->param.mount.need_dev = need_dev;
0160     r->param.mount.dev = &rdev;
0161     r->param.mount.dir = &rdir;
0162     r->param.mount.type = &rtype;
0163     r->param.mount.flags = flags;
0164     do {
0165         tomoyo_check_acl(r, tomoyo_check_mount_acl);
0166         error = tomoyo_audit_mount_log(r);
0167     } while (error == TOMOYO_RETRY_REQUEST);
0168  out:
0169     kfree(requested_dev_name);
0170     kfree(requested_dir_name);
0171     if (fstype)
0172         put_filesystem(fstype);
0173     kfree(requested_type);
0174     /* Drop refcount obtained by kern_path(). */
0175     if (obj.path1.dentry)
0176         path_put(&obj.path1);
0177     return error;
0178 }
0179
0180 /**
0181  * tomoyo_mount_permission - Check permission for mount() operation.
0182  *
0183  * @dev_name:  Name of device file. Maybe NULL.
0184  * @path:      Pointer to "struct path".
0185  * @type:      Name of filesystem type. Maybe NULL.
0186  * @flags:     Mount options.
0187  * @data_page: Optional data. Maybe NULL.
0188  *
0189  * Returns 0 on success, negative value otherwise.
0190  */
0191 int tomoyo_mount_permission(const char *dev_name, const struct path *path,
0192                 const char *type, unsigned long flags,
0193                 void *data_page)
0194 {
0195     struct tomoyo_request_info r;
0196     int error;
0197     int idx;
0198
0199     if (tomoyo_init_request_info(&r, NULL, TOMOYO_MAC_FILE_MOUNT)
0200         == TOMOYO_CONFIG_DISABLED)
0201         return 0;
0202     if ((flags & MS_MGC_MSK) == MS_MGC_VAL)
0203         flags &= ~MS_MGC_MSK;
0204     if (flags & MS_REMOUNT) {
0205         type = tomoyo_mounts[TOMOYO_MOUNT_REMOUNT];
0206         flags &= ~MS_REMOUNT;
0207     } else if (flags & MS_BIND) {
0208         type = tomoyo_mounts[TOMOYO_MOUNT_BIND];
0209         flags &= ~MS_BIND;
0210     } else if (flags & MS_SHARED) {
0211         if (flags & (MS_PRIVATE | MS_SLAVE | MS_UNBINDABLE))
0212             return -EINVAL;
0213         type = tomoyo_mounts[TOMOYO_MOUNT_MAKE_SHARED];
0214         flags &= ~MS_SHARED;
0215     } else if (flags & MS_PRIVATE) {
0216         if (flags & (MS_SHARED | MS_SLAVE | MS_UNBINDABLE))
0217             return -EINVAL;
0218         type = tomoyo_mounts[TOMOYO_MOUNT_MAKE_PRIVATE];
0219         flags &= ~MS_PRIVATE;
0220     } else if (flags & MS_SLAVE) {
0221         if (flags & (MS_SHARED | MS_PRIVATE | MS_UNBINDABLE))
0222             return -EINVAL;
0223         type = tomoyo_mounts[TOMOYO_MOUNT_MAKE_SLAVE];
0224         flags &= ~MS_SLAVE;
0225     } else if (flags & MS_UNBINDABLE) {
0226         if (flags & (MS_SHARED | MS_PRIVATE | MS_SLAVE))
0227             return -EINVAL;
0228         type = tomoyo_mounts[TOMOYO_MOUNT_MAKE_UNBINDABLE];
0229         flags &= ~MS_UNBINDABLE;
0230     } else if (flags & MS_MOVE) {
0231         type = tomoyo_mounts[TOMOYO_MOUNT_MOVE];
0232         flags &= ~MS_MOVE;
0233     }
0234     if (!type)
0235         type = "<NULL>";
0236     idx = tomoyo_read_lock();
0237     error = tomoyo_mount_acl(&r, dev_name, path, type, flags);
0238     tomoyo_read_unlock(idx);
0239     return error;
0240 }