Allow mounting snapshots in .zfs/snapshot as a regular user
Rather than doing a terrible credential swapping hack, we just check that the thing being mounted is a snapshot, and the mountpoint is the zfsctl directory, then we allow it. If the mount attempt is from inside a jail, on an unjailed dataset (mounted from the host, not by the jail), the ability to mount the snapshot is controlled by a new per-jail parameter: zfs.mount_snapshot Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Co-authored-by: Ryan Moeller <ryan@iXsystems.com> Signed-off-by: Ryan Moeller <ryan@iXsystems.com> Signed-off-by: Allan Jude <allan@klarasystems.com> Sponsored-by: Modirum MDPay Sponsored-by: Klara Inc. Closes #13758
This commit is contained in:
Allan Jude
Brian Behlendorf
parent
92e0d9d183
commit
5161e5d8a4
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@ -125,7 +125,6 @@ mount_snapshot(kthread_t *td, vnode_t **vpp, const char *fstype, char *fspath,
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struct vfsconf *vfsp;
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struct mount *mp;
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vnode_t *vp, *mvp;
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struct ucred *cr;
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int error;
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ASSERT_VOP_ELOCKED(*vpp, "mount_snapshot");
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@ -194,15 +193,8 @@ mount_snapshot(kthread_t *td, vnode_t **vpp, const char *fstype, char *fspath,
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* mount(8) and df(1) output.
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*/
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mp->mnt_flag |= MNT_IGNORE;
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/*
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* XXX: This is evil, but we can't mount a snapshot as a regular user.
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* XXX: Is is safe when snapshot is mounted from within a jail?
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*/
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cr = td->td_ucred;
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td->td_ucred = kcred;
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error = VFS_MOUNT(mp);
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td->td_ucred = cr;
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error = VFS_MOUNT(mp);
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if (error != 0) {
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/*
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* Clear VI_MOUNT and decrement the use count "atomically",
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@ -64,6 +64,7 @@
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#include <sys/dsl_dir.h>
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#include <sys/spa_boot.h>
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#include <sys/jail.h>
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#include <sys/osd.h>
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#include <ufs/ufs/quota.h>
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#include <sys/zfs_quota.h>
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@ -90,6 +91,20 @@ int zfs_debug_level;
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SYSCTL_INT(_vfs_zfs, OID_AUTO, debug, CTLFLAG_RWTUN, &zfs_debug_level, 0,
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"Debug level");
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struct zfs_jailparam {
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int mount_snapshot;
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};
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static struct zfs_jailparam zfs_jailparam0 = {
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.mount_snapshot = 0,
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};
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static int zfs_jailparam_slot;
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SYSCTL_JAIL_PARAM_SYS_NODE(zfs, CTLFLAG_RW, "Jail ZFS parameters");
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SYSCTL_JAIL_PARAM(_zfs, mount_snapshot, CTLTYPE_INT | CTLFLAG_RW, "I",
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"Allow mounting snapshots in the .zfs directory for unjailed datasets");
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SYSCTL_NODE(_vfs_zfs, OID_AUTO, version, CTLFLAG_RD, 0, "ZFS versions");
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static int zfs_version_acl = ZFS_ACL_VERSION;
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SYSCTL_INT(_vfs_zfs_version, OID_AUTO, acl, CTLFLAG_RD, &zfs_version_acl, 0,
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@ -1332,7 +1347,7 @@ zfs_mount(vfs_t *vfsp)
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char *osname;
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int error = 0;
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int canwrite;
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bool checkpointrewind;
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bool checkpointrewind, isctlsnap = false;
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if (vfs_getopt(vfsp->mnt_optnew, "from", (void **)&osname, NULL))
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return (SET_ERROR(EINVAL));
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@ -1347,6 +1362,7 @@ zfs_mount(vfs_t *vfsp)
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}
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fetch_osname_options(osname, &checkpointrewind);
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isctlsnap = (zfsctl_is_node(mvp) && strchr(osname, '@') != NULL);
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/*
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* Check for mount privilege?
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@ -1355,7 +1371,9 @@ zfs_mount(vfs_t *vfsp)
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* we have local permission to allow it
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*/
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error = secpolicy_fs_mount(cr, mvp, vfsp);
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if (error) {
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if (error && isctlsnap) {
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secpolicy_fs_mount_clearopts(cr, vfsp);
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} else if (error) {
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if (dsl_deleg_access(osname, ZFS_DELEG_PERM_MOUNT, cr) != 0)
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goto out;
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@ -1392,9 +1410,28 @@ zfs_mount(vfs_t *vfsp)
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*/
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if (!INGLOBALZONE(curproc) &&
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(!zone_dataset_visible(osname, &canwrite) || !canwrite)) {
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boolean_t mount_snapshot = B_FALSE;
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/*
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* Snapshots may be mounted in .zfs for unjailed datasets
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* if allowed by the jail param zfs.mount_snapshot.
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*/
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if (isctlsnap) {
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struct prison *pr;
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struct zfs_jailparam *zjp;
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pr = curthread->td_ucred->cr_prison;
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mtx_lock(&pr->pr_mtx);
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zjp = osd_jail_get(pr, zfs_jailparam_slot);
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mtx_unlock(&pr->pr_mtx);
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if (zjp && zjp->mount_snapshot)
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mount_snapshot = B_TRUE;
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}
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if (!mount_snapshot) {
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error = SET_ERROR(EPERM);
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goto out;
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}
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}
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vfsp->vfs_flag |= MNT_NFS4ACLS;
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@ -2343,3 +2380,236 @@ zfsvfs_update_fromname(const char *oldname, const char *newname)
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mtx_unlock(&mountlist_mtx);
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}
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#endif
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/*
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* Find a prison with ZFS info.
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* Return the ZFS info and the (locked) prison.
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*/
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static struct zfs_jailparam *
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zfs_jailparam_find(struct prison *spr, struct prison **prp)
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{
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struct prison *pr;
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struct zfs_jailparam *zjp;
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for (pr = spr; ; pr = pr->pr_parent) {
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mtx_lock(&pr->pr_mtx);
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if (pr == &prison0) {
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zjp = &zfs_jailparam0;
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break;
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}
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zjp = osd_jail_get(pr, zfs_jailparam_slot);
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if (zjp != NULL)
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break;
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mtx_unlock(&pr->pr_mtx);
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}
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*prp = pr;
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return (zjp);
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}
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/*
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* Ensure a prison has its own ZFS info. If zjpp is non-null, point it to the
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* ZFS info and lock the prison.
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*/
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static void
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zfs_jailparam_alloc(struct prison *pr, struct zfs_jailparam **zjpp)
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{
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struct prison *ppr;
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struct zfs_jailparam *zjp, *nzjp;
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void **rsv;
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/* If this prison already has ZFS info, return that. */
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zjp = zfs_jailparam_find(pr, &ppr);
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if (ppr == pr)
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goto done;
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/*
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* Allocate a new info record. Then check again, in case something
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* changed during the allocation.
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*/
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mtx_unlock(&ppr->pr_mtx);
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nzjp = malloc(sizeof (struct zfs_jailparam), M_PRISON, M_WAITOK);
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rsv = osd_reserve(zfs_jailparam_slot);
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zjp = zfs_jailparam_find(pr, &ppr);
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if (ppr == pr) {
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free(nzjp, M_PRISON);
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osd_free_reserved(rsv);
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goto done;
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}
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/* Inherit the initial values from the ancestor. */
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mtx_lock(&pr->pr_mtx);
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(void) osd_jail_set_reserved(pr, zfs_jailparam_slot, rsv, nzjp);
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(void) memcpy(nzjp, zjp, sizeof (*zjp));
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zjp = nzjp;
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mtx_unlock(&ppr->pr_mtx);
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done:
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if (zjpp != NULL)
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*zjpp = zjp;
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else
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mtx_unlock(&pr->pr_mtx);
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}
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/*
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* Jail OSD methods for ZFS VFS info.
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*/
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static int
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zfs_jailparam_create(void *obj, void *data)
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{
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struct prison *pr = obj;
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struct vfsoptlist *opts = data;
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int jsys;
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if (vfs_copyopt(opts, "zfs", &jsys, sizeof (jsys)) == 0 &&
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jsys == JAIL_SYS_INHERIT)
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return (0);
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/*
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* Inherit a prison's initial values from its parent
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* (different from JAIL_SYS_INHERIT which also inherits changes).
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*/
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zfs_jailparam_alloc(pr, NULL);
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return (0);
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}
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static int
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zfs_jailparam_get(void *obj, void *data)
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{
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struct prison *ppr, *pr = obj;
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struct vfsoptlist *opts = data;
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struct zfs_jailparam *zjp;
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int jsys, error;
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zjp = zfs_jailparam_find(pr, &ppr);
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jsys = (ppr == pr) ? JAIL_SYS_NEW : JAIL_SYS_INHERIT;
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error = vfs_setopt(opts, "zfs", &jsys, sizeof (jsys));
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if (error != 0 && error != ENOENT)
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goto done;
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if (jsys == JAIL_SYS_NEW) {
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error = vfs_setopt(opts, "zfs.mount_snapshot",
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&zjp->mount_snapshot, sizeof (zjp->mount_snapshot));
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if (error != 0 && error != ENOENT)
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goto done;
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} else {
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/*
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* If this prison is inheriting its ZFS info, report
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* empty/zero parameters.
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*/
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static int mount_snapshot = 0;
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error = vfs_setopt(opts, "zfs.mount_snapshot",
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&mount_snapshot, sizeof (mount_snapshot));
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if (error != 0 && error != ENOENT)
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goto done;
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}
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error = 0;
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done:
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mtx_unlock(&ppr->pr_mtx);
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return (error);
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}
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static int
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zfs_jailparam_set(void *obj, void *data)
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{
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struct prison *pr = obj;
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struct prison *ppr;
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struct vfsoptlist *opts = data;
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int error, jsys, mount_snapshot;
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/* Set the parameters, which should be correct. */
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error = vfs_copyopt(opts, "zfs", &jsys, sizeof (jsys));
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if (error == ENOENT)
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jsys = -1;
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error = vfs_copyopt(opts, "zfs.mount_snapshot", &mount_snapshot,
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sizeof (mount_snapshot));
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if (error == ENOENT)
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mount_snapshot = -1;
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else
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jsys = JAIL_SYS_NEW;
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if (jsys == JAIL_SYS_NEW) {
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/* "zfs=new" or "zfs.*": the prison gets its own ZFS info. */
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struct zfs_jailparam *zjp;
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/*
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* A child jail cannot have more permissions than its parent
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*/
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if (pr->pr_parent != &prison0) {
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zjp = zfs_jailparam_find(pr->pr_parent, &ppr);
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mtx_unlock(&ppr->pr_mtx);
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if (zjp->mount_snapshot < mount_snapshot) {
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return (EPERM);
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}
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}
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zfs_jailparam_alloc(pr, &zjp);
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if (mount_snapshot != -1)
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zjp->mount_snapshot = mount_snapshot;
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mtx_unlock(&pr->pr_mtx);
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} else {
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/* "zfs=inherit": inherit the parent's ZFS info. */
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mtx_lock(&pr->pr_mtx);
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osd_jail_del(pr, zfs_jailparam_slot);
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mtx_unlock(&pr->pr_mtx);
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}
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return (0);
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}
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static int
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zfs_jailparam_check(void *obj __unused, void *data)
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{
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struct vfsoptlist *opts = data;
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int error, jsys, mount_snapshot;
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/* Check that the parameters are correct. */
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error = vfs_copyopt(opts, "zfs", &jsys, sizeof (jsys));
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if (error != ENOENT) {
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if (error != 0)
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return (error);
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if (jsys != JAIL_SYS_NEW && jsys != JAIL_SYS_INHERIT)
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return (EINVAL);
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}
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error = vfs_copyopt(opts, "zfs.mount_snapshot", &mount_snapshot,
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sizeof (mount_snapshot));
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if (error != ENOENT) {
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if (error != 0)
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return (error);
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if (mount_snapshot != 0 && mount_snapshot != 1)
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return (EINVAL);
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}
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return (0);
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}
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static void
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zfs_jailparam_destroy(void *data)
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{
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free(data, M_PRISON);
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}
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static void
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zfs_jailparam_sysinit(void *arg __unused)
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{
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struct prison *pr;
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osd_method_t methods[PR_MAXMETHOD] = {
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[PR_METHOD_CREATE] = zfs_jailparam_create,
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[PR_METHOD_GET] = zfs_jailparam_get,
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[PR_METHOD_SET] = zfs_jailparam_set,
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[PR_METHOD_CHECK] = zfs_jailparam_check,
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};
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zfs_jailparam_slot = osd_jail_register(zfs_jailparam_destroy, methods);
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/* Copy the defaults to any existing prisons. */
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sx_slock(&allprison_lock);
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TAILQ_FOREACH(pr, &allprison, pr_list)
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zfs_jailparam_alloc(pr, NULL);
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sx_sunlock(&allprison_lock);
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}
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static void
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zfs_jailparam_sysuninit(void *arg __unused)
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{
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osd_jail_deregister(zfs_jailparam_slot);
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}
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SYSINIT(zfs_jailparam_sysinit, SI_SUB_DRIVERS, SI_ORDER_ANY,
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zfs_jailparam_sysinit, NULL);
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SYSUNINIT(zfs_jailparam_sysuninit, SI_SUB_DRIVERS, SI_ORDER_ANY,
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zfs_jailparam_sysuninit, NULL);
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