Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759609AbYAUV0e (ORCPT ); Mon, 21 Jan 2008 16:26:34 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1755561AbYAUV0A (ORCPT ); Mon, 21 Jan 2008 16:26:00 -0500 Received: from e5.ny.us.ibm.com ([32.97.182.145]:47058 "EHLO e5.ny.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757282AbYAUVZx (ORCPT ); Mon, 21 Jan 2008 16:25:53 -0500 Date: Mon, 21 Jan 2008 14:23:06 -0600 From: "Serge E. Hallyn" To: Miklos Szeredi Cc: akpm@linux-foundation.org, hch@infradead.org, serue@us.ibm.com, viro@ftp.linux.org.uk, kzak@redhat.com, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, containers@lists.osdl.org, util-linux-ng@vger.kernel.org Subject: Re: [patch 09/10] unprivileged mounts: propagation: inherit owner from parent Message-ID: <20080121202306.GA5536@sergelap.austin.rr.com> References: <20080116123147.466284860@szeredi.hu> <20080116123436.411935940@szeredi.hu> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20080116123436.411935940@szeredi.hu> User-Agent: Mutt/1.5.16 (2007-06-09) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 8385 Lines: 235 Quoting Miklos Szeredi (miklos@szeredi.hu): > From: Miklos Szeredi > > On mount propagation, let the owner of the clone be inherited from the > parent into which it has been propagated. > > If the parent has the "nosuid" flag, set this flag for the child as > well. This is needed for the suid-less namespace (use case #2 in the > first patch header), where all mounts are owned by the user and have > the nosuid flag set. In this case the propagated mount needs to have > nosuid, otherwise a suid executable may be misused by the user. > > Similar treatment is not needed for "nodev", because devices can't be > abused this way: the user is not able to gain privileges to devices by > rearranging the mount namespace. > > Signed-off-by: Miklos Szeredi As discussed many months ago this does seem like the most appropriate behavior for propagation. Acked-by: Serge Hallyn > --- > > Index: linux/fs/namespace.c > =================================================================== > --- linux.orig/fs/namespace.c 2008-01-16 13:25:09.000000000 +0100 > +++ linux/fs/namespace.c 2008-01-16 13:25:11.000000000 +0100 > @@ -506,10 +506,10 @@ static int reserve_user_mount(void) > return err; > } > > -static void __set_mnt_user(struct vfsmount *mnt) > +static void __set_mnt_user(struct vfsmount *mnt, uid_t owner) > { > WARN_ON(mnt->mnt_flags & MNT_USER); > - mnt->mnt_uid = current->fsuid; > + mnt->mnt_uid = owner; > mnt->mnt_flags |= MNT_USER; > > if (!capable(CAP_SETUID)) > @@ -520,7 +520,7 @@ static void __set_mnt_user(struct vfsmou > > static void set_mnt_user(struct vfsmount *mnt) > { > - __set_mnt_user(mnt); > + __set_mnt_user(mnt, current->fsuid); > spin_lock(&vfsmount_lock); > nr_user_mounts++; > spin_unlock(&vfsmount_lock); > @@ -536,7 +536,7 @@ static void clear_mnt_user(struct vfsmou > } > > static struct vfsmount *clone_mnt(struct vfsmount *old, struct dentry *root, > - int flag) > + int flag, uid_t owner) > { > struct super_block *sb = old->mnt_sb; > struct vfsmount *mnt; > @@ -560,7 +560,10 @@ static struct vfsmount *clone_mnt(struct > /* don't copy the MNT_USER flag */ > mnt->mnt_flags &= ~MNT_USER; > if (flag & CL_SETUSER) > - __set_mnt_user(mnt); > + __set_mnt_user(mnt, owner); > + > + if (flag & CL_NOSUID) > + mnt->mnt_flags |= MNT_NOSUID; > > if (flag & CL_SLAVE) { > list_add(&mnt->mnt_slave, &old->mnt_slave_list); > @@ -1066,7 +1069,7 @@ static int lives_below_in_same_fs(struct > } > > struct vfsmount *copy_tree(struct vfsmount *mnt, struct dentry *dentry, > - int flag) > + int flag, uid_t owner) > { > struct vfsmount *res, *p, *q, *r, *s; > struct nameidata nd; > @@ -1074,7 +1077,7 @@ struct vfsmount *copy_tree(struct vfsmou > if (!(flag & CL_COPY_ALL) && IS_MNT_UNBINDABLE(mnt)) > return ERR_PTR(-EPERM); > > - res = q = clone_mnt(mnt, dentry, flag); > + res = q = clone_mnt(mnt, dentry, flag, owner); > if (IS_ERR(q)) > goto error; > q->mnt_mountpoint = mnt->mnt_mountpoint; > @@ -1096,7 +1099,7 @@ struct vfsmount *copy_tree(struct vfsmou > p = s; > nd.path.mnt = q; > nd.path.dentry = p->mnt_mountpoint; > - q = clone_mnt(p, p->mnt_root, flag); > + q = clone_mnt(p, p->mnt_root, flag, owner); > if (IS_ERR(q)) > goto error; > spin_lock(&vfsmount_lock); > @@ -1121,7 +1124,7 @@ struct vfsmount *collect_mounts(struct v > { > struct vfsmount *tree; > down_read(&namespace_sem); > - tree = copy_tree(mnt, dentry, CL_COPY_ALL | CL_PRIVATE); > + tree = copy_tree(mnt, dentry, CL_COPY_ALL | CL_PRIVATE, 0); > up_read(&namespace_sem); > return tree; > } > @@ -1292,7 +1295,8 @@ static int do_change_type(struct nameida > */ > static int do_loopback(struct nameidata *nd, char *old_name, int flags) > { > - int clone_fl; > + int clone_fl = 0; > + uid_t owner = 0; > struct nameidata old_nd; > struct vfsmount *mnt = NULL; > int err; > @@ -1313,11 +1317,17 @@ static int do_loopback(struct nameidata > if (!check_mnt(nd->path.mnt) || !check_mnt(old_nd.path.mnt)) > goto out; > > - clone_fl = (flags & MS_SETUSER) ? CL_SETUSER : 0; > + if (flags & MS_SETUSER) { > + clone_fl |= CL_SETUSER; > + owner = current->fsuid; > + } > + > if (flags & MS_REC) > - mnt = copy_tree(old_nd.path.mnt, old_nd.path.dentry, clone_fl); > + mnt = copy_tree(old_nd.path.mnt, old_nd.path.dentry, clone_fl, > + owner); > else > - mnt = clone_mnt(old_nd.path.mnt, old_nd.path.dentry, clone_fl); > + mnt = clone_mnt(old_nd.path.mnt, old_nd.path.dentry, clone_fl, > + owner); > > err = PTR_ERR(mnt); > if (IS_ERR(mnt)) > @@ -1541,7 +1551,7 @@ static int do_new_mount(struct nameidata > } > > if (flags & MS_SETUSER) > - __set_mnt_user(mnt); > + __set_mnt_user(mnt, current->fsuid); > > return do_add_mount(mnt, nd, mnt_flags, NULL); > > @@ -1937,7 +1947,7 @@ static struct mnt_namespace *dup_mnt_ns( > down_write(&namespace_sem); > /* First pass: copy the tree topology */ > new_ns->root = copy_tree(mnt_ns->root, mnt_ns->root->mnt_root, > - CL_COPY_ALL | CL_EXPIRE); > + CL_COPY_ALL | CL_EXPIRE, 0); > if (IS_ERR(new_ns->root)) { > up_write(&namespace_sem); > kfree(new_ns); > Index: linux/fs/pnode.c > =================================================================== > --- linux.orig/fs/pnode.c 2008-01-16 13:25:07.000000000 +0100 > +++ linux/fs/pnode.c 2008-01-16 13:25:11.000000000 +0100 > @@ -181,15 +181,28 @@ int propagate_mnt(struct vfsmount *dest_ > > for (m = propagation_next(dest_mnt, dest_mnt); m; > m = propagation_next(m, dest_mnt)) { > - int type; > + int clflags; > + uid_t owner = 0; > struct vfsmount *source; > > if (IS_MNT_NEW(m)) > continue; > > - source = get_source(m, prev_dest_mnt, prev_src_mnt, &type); > + source = get_source(m, prev_dest_mnt, prev_src_mnt, &clflags); > > - child = copy_tree(source, source->mnt_root, type); > + if (m->mnt_flags & MNT_USER) { > + clflags |= CL_SETUSER; > + owner = m->mnt_uid; > + > + /* > + * If propagating into a user mount which doesn't > + * allow suid, then make sure, the child(ren) won't > + * allow suid either > + */ > + if (m->mnt_flags & MNT_NOSUID) > + clflags |= CL_NOSUID; > + } > + child = copy_tree(source, source->mnt_root, clflags, owner); > if (IS_ERR(child)) { > ret = PTR_ERR(child); > list_splice(tree_list, tmp_list.prev); > Index: linux/fs/pnode.h > =================================================================== > --- linux.orig/fs/pnode.h 2008-01-16 13:25:05.000000000 +0100 > +++ linux/fs/pnode.h 2008-01-16 13:25:11.000000000 +0100 > @@ -24,6 +24,7 @@ > #define CL_PROPAGATION 0x10 > #define CL_PRIVATE 0x20 > #define CL_SETUSER 0x40 > +#define CL_NOSUID 0x80 > > static inline void set_mnt_shared(struct vfsmount *mnt) > { > @@ -36,4 +37,6 @@ int propagate_mnt(struct vfsmount *, str > struct list_head *); > int propagate_umount(struct list_head *); > int propagate_mount_busy(struct vfsmount *, int); > +struct vfsmount *copy_tree(struct vfsmount *, struct dentry *, int, uid_t); > + > #endif /* _LINUX_PNODE_H */ > Index: linux/include/linux/fs.h > =================================================================== > --- linux.orig/include/linux/fs.h 2008-01-16 13:25:09.000000000 +0100 > +++ linux/include/linux/fs.h 2008-01-16 13:25:11.000000000 +0100 > @@ -1493,7 +1493,6 @@ extern int may_umount(struct vfsmount *) > extern void umount_tree(struct vfsmount *, int, struct list_head *); > extern void release_mounts(struct list_head *); > extern long do_mount(char *, char *, char *, unsigned long, void *); > -extern struct vfsmount *copy_tree(struct vfsmount *, struct dentry *, int); > extern void mnt_set_mountpoint(struct vfsmount *, struct dentry *, > struct vfsmount *); > extern struct vfsmount *collect_mounts(struct vfsmount *, struct dentry *); > > -- > - > To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/