Bind Mount Extensions ...

From: Herbert Poetzl
Date: Fri Sep 19 2003 - 14:30:58 EST


Hi Andrew!

just verified that the patch still applies on
linux-2.6.0-test5 and linux-2.6.0-test5-mm3
without any issues ...

FYI, this patch allows RO --bind mounts to
behave like other ro mounted filesystems ...

do you see any possibility to get this in
for extensive testing in the near future?

TIA,
Herbert


;
; Bind Mount Extensions
;
; this patch adds some functionality to the --bind
; type of vfs mounts.
;
; (C) 2003 Herbert Pötzl <herbert@xxxxxxxxxxxx>
;
; Changelog:
;
; 0.01 - readonly bind mounts
; 0.02 - added ro truncate handling
; - added ro (f)chown, (f)chmod handling
; 0.03 - added ro utime(s) handling
; - added ro access and *_ioctl
;
; this patch is free software; you can redistribute it and/or
; modify it under the terms of the GNU General Public License
; as published by the Free Software Foundation; either version 2
; of the License, or (at your option) any later version.
;
; this patch is distributed in the hope that it will be useful,
; but WITHOUT ANY WARRANTY; without even the implied warranty of
; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
; GNU General Public License for more details.
;

diff -NurP --minimal linux-2.6.0-test3/fs/ext2/ioctl.c linux-2.6.0-test3-bme0.03/fs/ext2/ioctl.c
--- linux-2.6.0-test3/fs/ext2/ioctl.c 2003-07-14 05:39:30.000000000 +0200
+++ linux-2.6.0-test3-bme0.03/fs/ext2/ioctl.c 2003-08-09 17:05:51.000000000 +0200
@@ -10,6 +10,7 @@
#include "ext2.h"
#include <linux/time.h>
#include <linux/sched.h>
+#include <linux/mount.h>
#include <asm/current.h>
#include <asm/uaccess.h>

@@ -29,7 +30,7 @@
case EXT2_IOC_SETFLAGS: {
unsigned int oldflags;

- if (IS_RDONLY(inode))
+ if (IS_RDONLY(inode) || MNT_IS_RDONLY(filp->f_vfsmnt))
return -EROFS;

if ((current->fsuid != inode->i_uid) && !capable(CAP_FOWNER))
@@ -68,7 +69,7 @@
case EXT2_IOC_SETVERSION:
if ((current->fsuid != inode->i_uid) && !capable(CAP_FOWNER))
return -EPERM;
- if (IS_RDONLY(inode))
+ if (IS_RDONLY(inode) || MNT_IS_RDONLY(filp->f_vfsmnt))
return -EROFS;
if (get_user(inode->i_generation, (int *) arg))
return -EFAULT;
diff -NurP --minimal linux-2.6.0-test3/fs/ext3/ioctl.c linux-2.6.0-test3-bme0.03/fs/ext3/ioctl.c
--- linux-2.6.0-test3/fs/ext3/ioctl.c 2003-07-14 05:33:10.000000000 +0200
+++ linux-2.6.0-test3-bme0.03/fs/ext3/ioctl.c 2003-08-09 17:06:08.000000000 +0200
@@ -12,6 +12,7 @@
#include <linux/ext3_fs.h>
#include <linux/ext3_jbd.h>
#include <linux/time.h>
+#include <linux/mount.h>
#include <asm/uaccess.h>


@@ -34,7 +35,7 @@
unsigned int oldflags;
unsigned int jflag;

- if (IS_RDONLY(inode))
+ if (IS_RDONLY(inode) || MNT_IS_RDONLY(filp->f_vfsmnt))
return -EROFS;

if ((current->fsuid != inode->i_uid) && !capable(CAP_FOWNER))
@@ -110,7 +111,7 @@

if ((current->fsuid != inode->i_uid) && !capable(CAP_FOWNER))
return -EPERM;
- if (IS_RDONLY(inode))
+ if (IS_RDONLY(inode) || MNT_IS_RDONLY(filp->f_vfsmnt))
return -EROFS;
if (get_user(generation, (int *) arg))
return -EFAULT;
diff -NurP --minimal linux-2.6.0-test3/fs/namei.c linux-2.6.0-test3-bme0.03/fs/namei.c
--- linux-2.6.0-test3/fs/namei.c 2003-08-09 16:31:27.000000000 +0200
+++ linux-2.6.0-test3-bme0.03/fs/namei.c 2003-08-09 16:37:42.000000000 +0200
@@ -207,10 +207,14 @@
{
int retval;
int submask;
+ umode_t mode = inode->i_mode;

/* Ordinary permission routines do not understand MAY_APPEND. */
submask = mask & ~MAY_APPEND;

+ if (nd && (mask & MAY_WRITE) && MNT_IS_RDONLY(nd->mnt) &&
+ (S_ISREG(mode) || S_ISDIR(mode) || S_ISLNK(mode)))
+ return -EROFS;
if (inode->i_op && inode->i_op->permission)
retval = inode->i_op->permission(inode, submask, nd);
else
@@ -1039,6 +1043,24 @@
return permission(dir,MAY_WRITE | MAY_EXEC, nd);
}

+static inline int mnt_may_create(struct vfsmount *mnt, struct inode *dir, struct dentry *child) {
+ if (child->d_inode)
+ return -EEXIST;
+ if (IS_DEADDIR(dir))
+ return -ENOENT;
+ if (mnt->mnt_flags & MNT_RDONLY)
+ return -EROFS;
+ return 0;
+}
+
+static inline int mnt_may_unlink(struct vfsmount *mnt, struct inode *dir, struct dentry *child) {
+ if (!child->d_inode)
+ return -ENOENT;
+ if (mnt->mnt_flags & MNT_RDONLY)
+ return -EROFS;
+ return 0;
+}
+
/*
* Special case: O_CREAT|O_EXCL implies O_NOFOLLOW for security
* reasons.
@@ -1160,7 +1182,8 @@
return -EACCES;

flag &= ~O_TRUNC;
- } else if (IS_RDONLY(inode) && (flag & FMODE_WRITE))
+ } else if ((IS_RDONLY(inode) || MNT_IS_RDONLY(nd->mnt)) &&
+ (flag & FMODE_WRITE))
return -EROFS;
/*
* An append-only file must be opened in append mode for writing.
@@ -1386,23 +1409,28 @@
struct dentry *lookup_create(struct nameidata *nd, int is_dir)
{
struct dentry *dentry;
+ int error;

down(&nd->dentry->d_inode->i_sem);
- dentry = ERR_PTR(-EEXIST);
+ error = -EEXIST;
if (nd->last_type != LAST_NORM)
- goto fail;
+ goto out;
nd->flags &= ~LOOKUP_PARENT;
dentry = lookup_hash(&nd->last, nd->dentry);
if (IS_ERR(dentry))
+ goto ret;
+ error = mnt_may_create(nd->mnt, nd->dentry->d_inode, dentry);
+ if (error)
goto fail;
+ error = -ENOENT;
if (!is_dir && nd->last.name[nd->last.len] && !dentry->d_inode)
- goto enoent;
+ goto fail;
+ret:
return dentry;
-enoent:
- dput(dentry);
- dentry = ERR_PTR(-ENOENT);
fail:
- return dentry;
+ dput(dentry);
+out:
+ return ERR_PTR(error);
}

int vfs_mknod(struct inode *dir, struct dentry *dentry, int mode, dev_t dev)
@@ -1627,7 +1655,11 @@
dentry = lookup_hash(&nd.last, nd.dentry);
error = PTR_ERR(dentry);
if (!IS_ERR(dentry)) {
+ error = mnt_may_unlink(nd.mnt, nd.dentry->d_inode, dentry);
+ if (error)
+ goto exit2;
error = vfs_rmdir(nd.dentry->d_inode, dentry);
+ exit2:
dput(dentry);
}
up(&nd.dentry->d_inode->i_sem);
@@ -1699,6 +1731,9 @@
/* Why not before? Because we want correct error value */
if (nd.last.name[nd.last.len])
goto slashes;
+ error = mnt_may_unlink(nd.mnt, nd.dentry->d_inode, dentry);
+ if (error)
+ goto exit2;
inode = dentry->d_inode;
if (inode)
atomic_inc(&inode->i_count);
@@ -2063,6 +2098,9 @@
error = -EINVAL;
if (old_dentry == trap)
goto exit4;
+ error = -EROFS;
+ if (MNT_IS_RDONLY(newnd.mnt))
+ goto exit4;
new_dentry = lookup_hash(&newnd.last, new_dir);
error = PTR_ERR(new_dentry);
if (IS_ERR(new_dentry))
diff -NurP --minimal linux-2.6.0-test3/fs/namespace.c linux-2.6.0-test3-bme0.03/fs/namespace.c
--- linux-2.6.0-test3/fs/namespace.c 2003-07-29 01:58:01.000000000 +0200
+++ linux-2.6.0-test3-bme0.03/fs/namespace.c 2003-08-09 18:40:30.000000000 +0200
@@ -225,7 +225,8 @@
seq_path(m, mnt, mnt->mnt_root, " \t\n\\");
seq_putc(m, ' ');
mangle(m, mnt->mnt_sb->s_type->name);
- seq_puts(m, mnt->mnt_sb->s_flags & MS_RDONLY ? " ro" : " rw");
+ seq_puts(m, (MNT_IS_RDONLY(mnt) ||
+ (mnt->mnt_sb->s_flags & MS_RDONLY)) ? " ro" : " rw");
for (fs_infop = fs_info; fs_infop->flag; fs_infop++) {
if (mnt->mnt_sb->s_flags & fs_infop->flag)
seq_puts(m, fs_infop->str);
@@ -516,11 +517,13 @@
/*
* 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, unsigned long flags, int mnt_flags)
{
struct nameidata old_nd;
struct vfsmount *mnt = NULL;
+ int recurse = flags & MS_REC;
int err = mount_is_safe(nd);
+
if (err)
return err;
if (!old_name || !*old_name)
@@ -547,6 +550,7 @@
spin_unlock(&vfsmount_lock);
} else
mntput(mnt);
+ mnt->mnt_flags = mnt_flags;
}

up_write(&current->namespace->sem);
@@ -750,6 +754,8 @@
return -EINVAL;

/* Separate the per-mountpoint flags */
+ if (flags & MS_RDONLY)
+ mnt_flags |= MNT_RDONLY;
if (flags & MS_NOSUID)
mnt_flags |= MNT_NOSUID;
if (flags & MS_NODEV)
@@ -771,7 +777,7 @@
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, mnt_flags);
else if (flags & MS_MOVE)
retval = do_move_mount(&nd, dev_name);
else
diff -NurP --minimal linux-2.6.0-test3/fs/open.c linux-2.6.0-test3-bme0.03/fs/open.c
--- linux-2.6.0-test3/fs/open.c 2003-08-09 16:31:27.000000000 +0200
+++ linux-2.6.0-test3-bme0.03/fs/open.c 2003-08-09 16:44:50.000000000 +0200
@@ -223,7 +223,7 @@
goto dput_and_out;

error = -EROFS;
- if (IS_RDONLY(inode))
+ if (IS_RDONLY(inode) || MNT_IS_RDONLY(nd.mnt))
goto dput_and_out;

error = -EPERM;
@@ -347,7 +347,7 @@
inode = nd.dentry->d_inode;

error = -EROFS;
- if (IS_RDONLY(inode))
+ if (IS_RDONLY(inode) || MNT_IS_RDONLY(nd.mnt))
goto dput_and_out;

/* Don't worry, the checks are done in inode_change_ok() */
@@ -396,7 +396,7 @@
inode = nd.dentry->d_inode;

error = -EROFS;
- if (IS_RDONLY(inode))
+ if (IS_RDONLY(inode) || MNT_IS_RDONLY(nd.mnt))
goto dput_and_out;

/* Don't worry, the checks are done in inode_change_ok() */
@@ -470,8 +470,9 @@
if (!res) {
res = permission(nd.dentry->d_inode, mode, &nd);
/* SuS v2 requires we report a read only fs too */
- if(!res && (mode & S_IWOTH) && IS_RDONLY(nd.dentry->d_inode)
- && !special_file(nd.dentry->d_inode->i_mode))
+ if (!res && (mode & S_IWOTH)
+ && !special_file(nd.dentry->d_inode->i_mode)
+ && (IS_RDONLY(nd.dentry->d_inode) || MNT_IS_RDONLY(nd.mnt)))
res = -EROFS;
path_release(&nd);
}
@@ -576,7 +576,7 @@
inode = dentry->d_inode;

err = -EROFS;
- if (IS_RDONLY(inode))
+ if (IS_RDONLY(inode) || MNT_IS_RDONLY(file->f_vfsmnt))
goto out_putf;
err = -EPERM;
if (IS_IMMUTABLE(inode) || IS_APPEND(inode))
@@ -608,7 +608,7 @@
inode = nd.dentry->d_inode;

error = -EROFS;
- if (IS_RDONLY(inode))
+ if (IS_RDONLY(inode) || MNT_IS_RDONLY(nd.mnt))
goto dput_and_out;

error = -EPERM;
@@ -629,7 +629,7 @@
return error;
}

-static int chown_common(struct dentry * dentry, uid_t user, gid_t group)
+static int chown_common(struct vfsmount *mnt, struct dentry * dentry, uid_t user, gid_t group)
{
struct inode * inode;
int error;
@@ -641,7 +641,7 @@
goto out;
}
error = -EROFS;
- if (IS_RDONLY(inode))
+ if (IS_RDONLY(inode) || MNT_IS_RDONLY(mnt))
goto out;
error = -EPERM;
if (IS_IMMUTABLE(inode) || IS_APPEND(inode))
@@ -671,7 +671,7 @@

error = user_path_walk(filename, &nd);
if (!error) {
- error = chown_common(nd.dentry, user, group);
+ error = chown_common(nd.mnt, nd.dentry, user, group);
path_release(&nd);
}
return error;
@@ -684,7 +684,7 @@

error = user_path_walk_link(filename, &nd);
if (!error) {
- error = chown_common(nd.dentry, user, group);
+ error = chown_common(nd.mnt, nd.dentry, user, group);
path_release(&nd);
}
return error;
@@ -698,7 +698,7 @@

file = fget(fd);
if (file) {
- error = chown_common(file->f_dentry, user, group);
+ error = chown_common(file->f_vfsmnt, file->f_dentry, user, group);
fput(file);
}
return error;
diff -NurP --minimal linux-2.6.0-test3/fs/reiserfs/ioctl.c linux-2.6.0-test3-bme0.03/fs/reiserfs/ioctl.c
--- linux-2.6.0-test3/fs/reiserfs/ioctl.c 2003-07-14 05:33:11.000000000 +0200
+++ linux-2.6.0-test3-bme0.03/fs/reiserfs/ioctl.c 2003-08-09 17:06:22.000000000 +0200
@@ -5,6 +5,7 @@
#include <linux/fs.h>
#include <linux/reiserfs_fs.h>
#include <linux/time.h>
+#include <linux/mount.h>
#include <asm/uaccess.h>
#include <linux/pagemap.h>
#include <linux/smp_lock.h>
@@ -38,7 +39,7 @@
i_attrs_to_sd_attrs( inode, ( __u16 * ) &flags );
return put_user(flags, (int *) arg);
case REISERFS_IOC_SETFLAGS: {
- if (IS_RDONLY(inode))
+ if (IS_RDONLY(inode) || MNT_IS_RDONLY(filp->f_vfsmnt))
return -EROFS;

if ((current->fsuid != inode->i_uid) && !capable(CAP_FOWNER))
@@ -70,7 +71,7 @@
case REISERFS_IOC_SETVERSION:
if ((current->fsuid != inode->i_uid) && !capable(CAP_FOWNER))
return -EPERM;
- if (IS_RDONLY(inode))
+ if (IS_RDONLY(inode) || MNT_IS_RDONLY(filp->f_vfsmnt))
return -EROFS;
if (get_user(inode->i_generation, (int *) arg))
return -EFAULT;
diff -NurP --minimal linux-2.6.0-test3/include/linux/mount.h linux-2.6.0-test3-bme0.03/include/linux/mount.h
--- linux-2.6.0-test3/include/linux/mount.h 2003-07-14 05:30:35.000000000 +0200
+++ linux-2.6.0-test3-bme0.03/include/linux/mount.h 2003-08-09 16:37:42.000000000 +0200
@@ -14,9 +14,10 @@

#include <linux/list.h>

-#define MNT_NOSUID 1
-#define MNT_NODEV 2
-#define MNT_NOEXEC 4
+#define MNT_RDONLY 1
+#define MNT_NOSUID 2
+#define MNT_NODEV 4
+#define MNT_NOEXEC 8

struct vfsmount
{
@@ -33,6 +34,8 @@
struct list_head mnt_list;
};

+#define MNT_IS_RDONLY(m) ((m)->mnt_flags & MNT_RDONLY)
+
static inline struct vfsmount *mntget(struct vfsmount *mnt)
{
if (mnt)


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