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Commit 4f757f3c authored by Al Viro's avatar Al Viro
Browse files

make sure that mntns_install() doesn't end up with referral for root 



new flag: LOOKUP_DOWN.  If the starting point is overmounted, cross
into whatever's mounted on top, triggering referrals et.al.

Use that instead of follow_down_one() loop in mntns_install(), handle
errors properly.

Signed-off-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
parent 93893862

fs/namei.c

+38 −0
Original line number Diff line number Diff line
@@ -2252,6 +2252,35 @@ static inline int lookup_last(struct nameidata *nd) 
	return walk_component(nd, 0);

}



static int handle_lookup_down(struct nameidata *nd)

{

	struct path path = nd->path;

	struct inode *inode = nd->inode;

	unsigned seq = nd->seq;

	int err;



	if (nd->flags & LOOKUP_RCU) {

		/*

		 * don't bother with unlazy_walk on failure - we are

		 * at the very beginning of walk, so we lose nothing

		 * if we simply redo everything in non-RCU mode

		 */

		if (unlikely(!__follow_mount_rcu(nd, &path, &inode, &seq)))

			return -ECHILD;

	} else {

		dget(path.dentry);

		err = follow_managed(&path, nd);

		if (unlikely(err < 0))

			return err;

		inode = d_backing_inode(path.dentry);

		seq = 0;

	}

	path_to_nameidata(&path, nd);

	nd->inode = inode;

	nd->seq = seq;

	return 0;

}



/* Returns 0 and nd will be valid on success; Retuns error, otherwise. */

static int path_lookupat(struct nameidata *nd, unsigned flags, struct path *path)

{
@@ -2260,6 +2289,15 @@ static int path_lookupat(struct nameidata *nd, unsigned flags, struct path *path 


	if (IS_ERR(s))

		return PTR_ERR(s);



	if (unlikely(flags & LOOKUP_DOWN)) {

		err = handle_lookup_down(nd);

		if (unlikely(err < 0)) {

			terminate_walk(nd);

			return err;

		}

	}



	while (!(err = link_path_walk(s, nd))

		&& ((err = lookup_last(nd)) > 0)) {

		s = trailing_symlink(nd);

fs/namespace.c

+11 −7
Original line number Diff line number Diff line
@@ -3465,8 +3465,9 @@ static void mntns_put(struct ns_common *ns) 
static int mntns_install(struct nsproxy *nsproxy, struct ns_common *ns)

{

	struct fs_struct *fs = current->fs;

	struct mnt_namespace *mnt_ns = to_mnt_ns(ns);

	struct mnt_namespace *mnt_ns = to_mnt_ns(ns), *old_mnt_ns;

	struct path root;

	int err;



	if (!ns_capable(mnt_ns->user_ns, CAP_SYS_ADMIN) ||

	    !ns_capable(current_user_ns(), CAP_SYS_CHROOT) ||
@@ -3477,15 +3478,18 @@ static int mntns_install(struct nsproxy *nsproxy, struct ns_common *ns) 
		return -EINVAL;



	get_mnt_ns(mnt_ns);

	put_mnt_ns(nsproxy->mnt_ns);

	old_mnt_ns = nsproxy->mnt_ns;

	nsproxy->mnt_ns = mnt_ns;



	/* Find the root */

	root.mnt    = &mnt_ns->root->mnt;

	root.dentry = mnt_ns->root->mnt.mnt_root;

	path_get(&root);

	while(d_mountpoint(root.dentry) && follow_down_one(&root))

		;

	err = vfs_path_lookup(mnt_ns->root->mnt.mnt_root, &mnt_ns->root->mnt,

				"/", LOOKUP_DOWN, &root);

	if (err) {

		/* revert to old namespace */

		nsproxy->mnt_ns = old_mnt_ns;

		put_mnt_ns(mnt_ns);

		return err;

	}



	/* Update the pwd and root */

	set_fs_pwd(fs, &root);

include/linux/namei.h

+1 −0
Original line number Diff line number Diff line
@@ -44,6 +44,7 @@ enum {LAST_NORM, LAST_ROOT, LAST_DOT, LAST_DOTDOT, LAST_BIND}; 
#define LOOKUP_JUMPED		0x1000

#define LOOKUP_ROOT		0x2000

#define LOOKUP_EMPTY		0x4000

#define LOOKUP_DOWN		0x8000



extern int path_pts(struct path *path);