From afac7cba7ed31968a95e181dc25e204e45009ea8 Mon Sep 17 00:00:00 2001 From: Al Viro Date: Wed, 23 Nov 2011 19:34:49 -0500 Subject: vfs: more mnt_parent cleanups a) mount --move is checking that ->mnt_parent is non-NULL before looking if that parent happens to be shared; ->mnt_parent is never NULL and it's not even an misspelled !mnt_has_parent() b) pivot_root open-codes is_path_reachable(), poorly. c) so does path_is_under(), while we are at it. Signed-off-by: Al Viro --- fs/namespace.c | 42 +++++++++++++++++++++++++++--------------- 1 file changed, 27 insertions(+), 15 deletions(-) (limited to 'fs/namespace.c') diff --git a/fs/namespace.c b/fs/namespace.c index ec8512478b04..7aad258dcaf6 100644 --- a/fs/namespace.c +++ b/fs/namespace.c @@ -1876,8 +1876,7 @@ static int do_move_mount(struct path *path, char *old_name) /* * Don't move a mount residing in a shared parent. */ - if (old_path.mnt->mnt_parent && - IS_MNT_SHARED(old_path.mnt->mnt_parent)) + if (IS_MNT_SHARED(old_path.mnt->mnt_parent)) goto out1; /* * Don't move a mount tree containing unbindable mounts to a destination @@ -2533,6 +2532,31 @@ out_type: return ret; } +/* + * Return true if path is reachable from root + * + * namespace_sem or vfsmount_lock is held + */ +bool is_path_reachable(struct vfsmount *mnt, struct dentry *dentry, + const struct path *root) +{ + while (mnt != root->mnt && mnt_has_parent(mnt)) { + dentry = mnt->mnt_mountpoint; + mnt = mnt->mnt_parent; + } + return mnt == root->mnt && is_subdir(dentry, root->dentry); +} + +int path_is_under(struct path *path1, struct path *path2) +{ + int res; + br_read_lock(vfsmount_lock); + res = is_path_reachable(path1->mnt, path1->dentry, path2); + br_read_unlock(vfsmount_lock); + return res; +} +EXPORT_SYMBOL(path_is_under); + /* * pivot_root Semantics: * Moves the root file system of the current process to the directory put_old, @@ -2561,7 +2585,6 @@ out_type: SYSCALL_DEFINE2(pivot_root, const char __user *, new_root, const char __user *, put_old) { - struct vfsmount *tmp; struct path new, old, parent_path, root_parent, root; int error; @@ -2611,18 +2634,7 @@ SYSCALL_DEFINE2(pivot_root, const char __user *, new_root, if (!mnt_has_parent(new.mnt)) goto out4; /* not attached */ /* make sure we can reach put_old from new_root */ - tmp = old.mnt; - if (tmp != new.mnt) { - for (;;) { - if (!mnt_has_parent(tmp)) - goto out4; /* already mounted on put_old */ - if (tmp->mnt_parent == new.mnt) - break; - tmp = tmp->mnt_parent; - } - if (!is_subdir(tmp->mnt_mountpoint, new.dentry)) - goto out4; - } else if (!is_subdir(old.dentry, new.dentry)) + if (!is_path_reachable(old.mnt, old.dentry, &new)) goto out4; br_write_lock(vfsmount_lock); detach_mnt(new.mnt, &parent_path); -- cgit v1.2.3-58-ga151