From: Miklos Szeredi Add ownership information to mounts. A new mount flag, MS_SETUSER is used to make a mount owned by a user. If this flag is specified, then the owner will be set to the current real user id and the mount will be marked with the MNT_USER flag. On remount don't preserve previous owner, and treat MS_SETUSER as for a new mount. The MS_SETUSER flag is ignored on mount move. The MNT_USER flag is not copied on any kind of mount cloning: namespace creation, binding or propagation. For bind mounts the cloned mount(s) are set to MNT_USER depending on the MS_SETUSER mount flag. In all the other cases MNT_USER is always cleared. For MNT_USER mounts a "user=UID" option is added to /proc/PID/mounts. This is compatible with how mount ownership is stored in /etc/mtab. It is expected, that in the future mount(8) will use MS_SETUSER to store mount ownership within the kernel. This would help in situations, where /etc/mtab is difficult or impossible to work with, e.g. when using mount propagation. Signed-off-by: Miklos Szeredi --- Index: linux/fs/namespace.c =================================================================== --- linux.orig/fs/namespace.c 2007-04-11 18:27:46.000000000 +0200 +++ linux/fs/namespace.c 2007-04-11 20:07:51.000000000 +0200 @@ -227,6 +227,13 @@ static struct vfsmount *skip_mnt_tree(st return p; } +static void set_mnt_user(struct vfsmount *mnt) +{ + BUG_ON(mnt->mnt_flags & MNT_USER); + mnt->mnt_uid = current->uid; + mnt->mnt_flags |= MNT_USER; +} + static struct vfsmount *clone_mnt(struct vfsmount *old, struct dentry *root, int flag) { @@ -241,6 +248,11 @@ static struct vfsmount *clone_mnt(struct mnt->mnt_mountpoint = mnt->mnt_root; mnt->mnt_parent = mnt; + /* don't copy the MNT_USER flag */ + mnt->mnt_flags &= ~MNT_USER; + if (flag & CL_SETUSER) + set_mnt_user(mnt); + if (flag & CL_SLAVE) { list_add(&mnt->mnt_slave, &old->mnt_slave_list); mnt->mnt_master = old; @@ -403,6 +415,8 @@ static int show_vfsmnt(struct seq_file * if (mnt->mnt_flags & fs_infop->flag) seq_puts(m, fs_infop->str); } + if (mnt->mnt_flags & MNT_USER) + seq_printf(m, ",user=%i", mnt->mnt_uid); if (mnt->mnt_sb->s_op->show_options) err = mnt->mnt_sb->s_op->show_options(m, mnt); seq_puts(m, " 0 0\n"); @@ -920,8 +934,9 @@ static int do_change_type(struct nameida /* * do loopback mount. */ -static int do_loopback(struct nameidata *nd, char *old_name, int recurse) +static int do_loopback(struct nameidata *nd, char *old_name, int flags) { + int clone_flags; struct nameidata old_nd; struct vfsmount *mnt = NULL; int err = mount_is_safe(nd); @@ -941,11 +956,12 @@ static int do_loopback(struct nameidata if (!check_mnt(nd->mnt) || !check_mnt(old_nd.mnt)) goto out; + clone_flags = (flags & MS_SETUSER) ? CL_SETUSER : 0; err = -ENOMEM; - if (recurse) - mnt = copy_tree(old_nd.mnt, old_nd.dentry, 0); + if (flags & MS_REC) + mnt = copy_tree(old_nd.mnt, old_nd.dentry, clone_flags); else - mnt = clone_mnt(old_nd.mnt, old_nd.dentry, 0); + mnt = clone_mnt(old_nd.mnt, old_nd.dentry, clone_flags); if (!mnt) goto out; @@ -987,8 +1003,11 @@ static int do_remount(struct nameidata * down_write(&sb->s_umount); err = do_remount_sb(sb, flags, data, 0); - if (!err) + if (!err) { nd->mnt->mnt_flags = mnt_flags; + if (flags & MS_SETUSER) + set_mnt_user(nd->mnt); + } up_write(&sb->s_umount); if (!err) security_sb_post_remount(nd->mnt, flags, data); @@ -1093,10 +1112,13 @@ static int do_new_mount(struct nameidata if (!capable(CAP_SYS_ADMIN)) return -EPERM; - mnt = do_kern_mount(type, flags, name, data); + mnt = do_kern_mount(type, flags & ~MS_SETUSER, name, data); if (IS_ERR(mnt)) return PTR_ERR(mnt); + if (flags & MS_SETUSER) + set_mnt_user(mnt); + return do_add_mount(mnt, nd, mnt_flags, NULL); } @@ -1127,7 +1149,8 @@ int do_add_mount(struct vfsmount *newmnt if (S_ISLNK(newmnt->mnt_root->d_inode->i_mode)) goto unlock; - newmnt->mnt_flags = mnt_flags; + /* MNT_USER was set earlier */ + newmnt->mnt_flags |= mnt_flags; if ((err = graft_tree(newmnt, nd))) goto unlock; @@ -1447,7 +1470,7 @@ long do_mount(char *dev_name, char *dir_ retval = do_remount(&nd, flags & ~MS_REMOUNT, mnt_flags, data_page); else if (flags & MS_BIND) - retval = do_loopback(&nd, dev_name, flags & MS_REC); + retval = do_loopback(&nd, dev_name, flags); else if (flags & (MS_SHARED | MS_PRIVATE | MS_SLAVE | MS_UNBINDABLE)) retval = do_change_type(&nd, flags); else if (flags & MS_MOVE) Index: linux/include/linux/fs.h =================================================================== --- linux.orig/include/linux/fs.h 2007-04-11 18:27:46.000000000 +0200 +++ linux/include/linux/fs.h 2007-04-11 20:07:51.000000000 +0200 @@ -123,6 +123,7 @@ extern int dir_notify_enable; #define MS_SLAVE (1<<19) /* change to slave */ #define MS_SHARED (1<<20) /* change to shared */ #define MS_RELATIME (1<<21) /* Update atime relative to mtime/ctime. */ +#define MS_SETUSER (1<<22) /* set mnt_uid to current user */ #define MS_ACTIVE (1<<30) #define MS_NOUSER (1<<31) Index: linux/include/linux/mount.h =================================================================== --- linux.orig/include/linux/mount.h 2007-04-11 18:27:33.000000000 +0200 +++ linux/include/linux/mount.h 2007-04-11 20:07:51.000000000 +0200 @@ -28,6 +28,7 @@ struct mnt_namespace; #define MNT_NOATIME 0x08 #define MNT_NODIRATIME 0x10 #define MNT_RELATIME 0x20 +#define MNT_USER 0x40 #define MNT_SHRINKABLE 0x100 @@ -61,6 +62,8 @@ struct vfsmount { atomic_t mnt_count; int mnt_expiry_mark; /* true if marked for expiry */ int mnt_pinned; + + uid_t mnt_uid; /* owner of the mount */ }; static inline struct vfsmount *mntget(struct vfsmount *mnt) Index: linux/fs/pnode.h =================================================================== --- linux.orig/fs/pnode.h 2007-02-04 19:44:54.000000000 +0100 +++ linux/fs/pnode.h 2007-04-11 20:07:51.000000000 +0200 @@ -22,6 +22,7 @@ #define CL_COPY_ALL 0x04 #define CL_MAKE_SHARED 0x08 #define CL_PROPAGATION 0x10 +#define CL_SETUSER 0x20 static inline void set_mnt_shared(struct vfsmount *mnt) { -- - 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/