/* * CDDL HEADER START * * The contents of this file are subject to the terms of the * Common Development and Distribution License (the "License"). * You may not use this file except in compliance with the License. * * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE * or http://www.opensolaris.org/os/licensing. * See the License for the specific language governing permissions * and limitations under the License. * * When distributing Covered Code, include this CDDL HEADER in each * file and include the License file at usr/src/OPENSOLARIS.LICENSE. * If applicable, add the following below this CDDL HEADER, with the * fields enclosed by brackets "[]" replaced with your own identifying * information: Portions Copyright [yyyy] [name of copyright owner] * * CDDL HEADER END */ /* * Copyright 2010 Sun Microsystems, Inc. All rights reserved. * Use is subject to license terms. */ /* Copyright (c) 1983, 1984, 1985, 1986, 1987, 1988, 1989 AT&T */ /* All Rights Reserved */ /* * Portions of this source code were derived from Berkeley 4.3 BSD * under license from the Regents of the University of California. */ #include <sys/types.h> #include <sys/t_lock.h> #include <sys/param.h> #include <sys/errno.h> #include <sys/fstyp.h> #include <sys/kmem.h> #include <sys/systm.h> #include <sys/mount.h> #include <sys/vfs.h> #include <sys/cred.h> #include <sys/vnode.h> #include <sys/cmn_err.h> #include <sys/debug.h> #include <sys/pathname.h> #include <sys/policy.h> #include <sys/zone.h> #define UMOUNT2_SET_ERRNO(e, is_syscall) ((is_syscall) ? set_errno((e)) : (e)) /* * The heart of the umount2 call - it is pulled out to allow kernel * level particpation when the only reference is the vfs pointer. * * Note that some of the callers may not be in the context of a * syscall (created by zthread_create() for example) and as such * may not have an associated curthread->t_lwp. This is handled * by is_syscall. */ int umount2_engine(vfs_t *vfsp, int flag, cred_t *cr, int is_syscall) { int error; /* * Protect the call to vn_vfswlock() with the vfs reflock. This * ensures vfs_vnodecovered will either be NULL (because someone * beat us to the umount) or valid (because vfs_lock() prevents * another umount from getting through here until we've called * vn_vfswlock() on the covered vnode). * * At one point, we did the non-blocking version (vfs_lock()), * and if it failed, bailed out with EBUSY. However, dounmount() * calls vfs_lock_wait() and we drop the vfs lock before calling * dounmount(), so there's no difference between waiting here * for the lock or waiting there because grabbed it as soon as * we drop it below. No returning with EBUSY at this point * reduces the number of spurious unmount failures that happen * as a side-effect of fsflush() and other mount and unmount * operations that might be going on simultaneously. */ vfs_lock_wait(vfsp); /* * Call vn_vfswlock() on the covered vnode so that dounmount() * can do its thing. It will call the corresponding vn_vfsunlock(). * Note that vfsp->vfs_vnodecovered can be NULL here, either because * someone did umount on "/" or because someone beat us to the umount * before we did the vfs_lock() above. In these cases, vn_vfswlock() * returns EBUSY and we just pass that up. Also note that we're * looking at a vnode without doing a VN_HOLD() on it. This is * safe because it can't go away while something is mounted on it * and we're locking out other umounts at this point. */ if (vn_vfswlock(vfsp->vfs_vnodecovered)) { vfs_unlock(vfsp); VFS_RELE(vfsp); return (UMOUNT2_SET_ERRNO(EBUSY, is_syscall)); } /* * Now that the VVFSLOCK in the covered vnode is protecting this * path, we don't need the vfs reflock or the hold on the vfs anymore. */ vfs_unlock(vfsp); VFS_RELE(vfsp); /* * Perform the unmount. */ if ((error = dounmount(vfsp, flag, cr)) != 0) return (UMOUNT2_SET_ERRNO(error, is_syscall)); return (0); } /* * New umount() system call (for force unmount flag and perhaps others later). */ int umount2(char *pathp, int flag) { struct pathname pn; struct vfs *vfsp; int error; /* * Some flags are disallowed through the system call interface. */ flag &= MS_UMOUNT_MASK; /* * Lookup user-supplied name by trying to match it against the * mount points recorded at mount time. If no match is found * (which can happen if the path to the mount point is specified * differently between mount & umount, or if a block device were * passed to umount) then we fall back to calling lookupname() * to find the vfs. Doing it this way prevents calling lookupname() * in most cases and that allows forcible umount to work even if * lookupname() would hang (i.e. because an NFS server is dead). */ if (error = pn_get(pathp, UIO_USERSPACE, &pn)) return (set_errno(error)); /* * Only a privileged user is allowed to bypass the security * checks done by lookupname() and use the results from * vfs_mntpoint2vfsp() instead. It could be argued that the * proper check is FILE_DAC_SEARCH but we put it all * under the mount privilege. Also, make sure the caller * isn't in an environment with an alternate root (to the zone's root) * directory, i.e. chroot(2). */ if (secpolicy_fs_unmount(CRED(), NULL) != 0 || (PTOU(curproc)->u_rdir != NULL && PTOU(curproc)->u_rdir != curproc->p_zone->zone_rootvp) || (vfsp = vfs_mntpoint2vfsp(pn.pn_path)) == NULL) { vnode_t *fsrootvp; /* fall back to lookupname() on path given to us */ if (error = lookupname(pn.pn_path, UIO_SYSSPACE, FOLLOW, NULLVPP, &fsrootvp)) { pn_free(&pn); return (set_errno(error)); } /* * Find the vfs to be unmounted. The caller may have specified * either the directory mount point (preferred) or else (for a * disk-based file system) the block device which was mounted. * Check to see which it is; if it's the device, search the VFS * list to find the associated vfs entry. */ if (fsrootvp->v_flag & VROOT) { vfsp = fsrootvp->v_vfsp; VFS_HOLD(vfsp); } else if (fsrootvp->v_type == VBLK) vfsp = vfs_dev2vfsp(fsrootvp->v_rdev); else vfsp = NULL; VN_RELE(fsrootvp); if (vfsp == NULL) { pn_free(&pn); return (set_errno(EINVAL)); } } pn_free(&pn); return (umount2_engine(vfsp, flag, CRED(), 1)); }
