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Subject[PATCH][CFT] selective nosuid/noexec/nodev
	Folks, patch below (_completely_ untested) is a backport of
a neat stuff from namespace-patch.

It does (OK, is supposed to do) the following: make noexec, nosuid
and nodev properties of vfsmount, not superblock.

In other words, different instances of the same fs may differ in
these flags.

It has quite a few lovely uses. Example:

I'm sick and tired of a little skript k1dd13 wannabe (who happens to be
a son of $BIG_BOSS and thus is a holy cow). I want to make his $HOME
noexec (all public writable places already are). I don't want to
bother with giving him a partition of his own and I don't want to screw
normal users.

Solution:
mount --bind /home/little_wanker /home/little_wanker
mount -o remount,noexec /home/little_wanker

Opposite examples (selectively allowing exec or suid on subtrees of
fs that is otherwise noexec/nosuid) are along the same lines. We can
even do it for individual files ;-)

More serious applications may be in situations when we want to set a
chroot environment with selective (or global, for that matter)
removal/allowing suid/exec/dev without messing everything else.

Patch is pretty straightforward - in call cases when we did
IS_NOSUID(), etc. we have relevant struct vfsmount, so we can check
->mnt_flags instead of ->s_flags. do_mount() separates these flags
from the rest and does the (obvious) right thing. That, and we have
to look both at ->mnt_sb->s_flags and ->mnt_flags when we read from
/proc/mounts.

You are welcome to play with it ;-) Its equivalent works fine
in full namespace patch. This is a backport, and all I promise is
that it builds. Help with testing is welcome.

Al

diff -urN S5-pre4/arch/sparc64/solaris/fs.c S5-pre4-noexe/arch/sparc64/solaris/fs.c
--- S5-pre4/arch/sparc64/solaris/fs.c Thu Feb 22 06:47:53 2001
+++ S5-pre4-noexe/arch/sparc64/solaris/fs.c Sun May 20 12:50:36 2001
@@ -406,21 +406,21 @@
u32 f_filler[16];
};

-static int report_statvfs(struct inode *inode, u32 buf)
+static int report_statvfs(struct vfsmount *mnt, struct inode *inode, u32 buf)
{
struct statfs s;
int error;
struct sol_statvfs *ss = (struct sol_statvfs *)A(buf);

- error = vfs_statfs(inode->i_sb, &s);
+ error = vfs_statfs(mnt->mnt_sb, &s);
if (!error) {
- const char *p = inode->i_sb->s_type->name;
+ const char *p = mnt->mnt_sb->s_type->name;
int i = 0;
int j = strlen (p);

if (j > 15) j = 15;
if (IS_RDONLY(inode)) i = 1;
- if (IS_NOSUID(inode)) i |= 2;
+ if (mnt->mnt_flags & MNT_NOSUID) i |= 2;
if (put_user (s.f_bsize, &ss->f_bsize) ||
__put_user (0, &ss->f_frsize) ||
__put_user (s.f_blocks, &ss->f_blocks) ||
@@ -440,21 +440,21 @@
return error;
}

-static int report_statvfs64(struct inode *inode, u32 buf)
+static int report_statvfs64(struct vfsmount *mnt, struct inode *inode, u32 buf)
{
struct statfs s;
int error;
struct sol_statvfs64 *ss = (struct sol_statvfs64 *)A(buf);

- error = vfs_statfs(inode->i_sb, &s);
+ error = vfs_statfs(mnt->mnt_sb, &s);
if (!error) {
- const char *p = inode->i_sb->s_type->name;
+ const char *p = mnt->mnt_sb->s_type->name;
int i = 0;
int j = strlen (p);

if (j > 15) j = 15;
if (IS_RDONLY(inode)) i = 1;
- if (IS_NOSUID(inode)) i |= 2;
+ if (mnt->mnt_flags & MNT_NOSUID) i |= 2;
if (put_user (s.f_bsize, &ss->f_bsize) ||
__put_user (0, &ss->f_frsize) ||
__put_user (s.f_blocks, &ss->f_blocks) ||
@@ -482,7 +482,7 @@
error = user_path_walk((const char *)A(path),&nd);
if (!error) {
struct inode * inode = nd.dentry->d_inode;
- error = report_statvfs(inode, buf);
+ error = report_statvfs(nd.mnt, inode, buf);
path_release(&nd);
}
return error;
@@ -496,7 +496,7 @@
error = -EBADF;
file = fget(fd);
if (file) {
- error = report_statvfs(file->f_dentry->d_inode, buf);
+ error = report_statvfs(file->f_vfsmnt, file->f_dentry->d_inode, buf);
fput(file);
}

@@ -512,7 +512,7 @@
error = user_path_walk((const char *)A(path), &nd);
if (!error) {
struct inode * inode = nd.dentry->d_inode;
- error = report_statvfs64(inode, buf);
+ error = report_statvfs64(nd.mnt, inode, buf);
path_release(&nd);
}
unlock_kernel();
@@ -528,7 +528,7 @@
file = fget(fd);
if (file) {
lock_kernel();
- error = report_statvfs64(file->f_dentry->d_inode, buf);
+ error = report_statvfs64(file->f_vfsmnt, file->f_dentry->d_inode, buf);
unlock_kernel();
fput(file);
}
diff -urN S5-pre4/fs/exec.c S5-pre4-noexe/fs/exec.c
--- S5-pre4/fs/exec.c Sat Apr 28 02:12:56 2001
+++ S5-pre4-noexe/fs/exec.c Sun May 20 12:46:46 2001
@@ -347,7 +347,8 @@
if (!err) {
inode = nd.dentry->d_inode;
file = ERR_PTR(-EACCES);
- if (!IS_NOEXEC(inode) && S_ISREG(inode->i_mode)) {
+ if (!(nd.mnt->mnt_flags & MNT_NOEXEC) &&
+ S_ISREG(inode->i_mode)) {
int err = permission(inode, MAY_EXEC);
file = ERR_PTR(err);
if (!err) {
@@ -615,7 +616,7 @@
bprm->e_uid = current->euid;
bprm->e_gid = current->egid;

- if(!IS_NOSUID(inode)) {
+ if(!(bprm->file->f_vfsmnt->mnt_flags & MNT_NOSUID)) {
/* Set-uid? */
if (mode & S_ISUID)
bprm->e_uid = inode->i_uid;
diff -urN S5-pre4/fs/fat/inode.c S5-pre4-noexe/fs/fat/inode.c
--- S5-pre4/fs/fat/inode.c Sat Apr 28 02:12:56 2001
+++ S5-pre4-noexe/fs/fat/inode.c Sun May 20 12:48:59 2001
@@ -806,9 +806,8 @@
MSDOS_I(inode)->mmu_private = inode->i_size;
} else { /* not a directory */
inode->i_mode = MSDOS_MKMODE(de->attr,
- ((IS_NOEXEC(inode) ||
- (sbi->options.showexec &&
- !is_exec(de->ext)))
+ ((sbi->options.showexec &&
+ !is_exec(de->ext))
? S_IRUGO|S_IWUGO : S_IRWXUGO)
& ~sbi->options.fs_umask) | S_IFREG;
MSDOS_I(inode)->i_start = CF_LE_W(de->start);
@@ -927,9 +926,7 @@

inode_setattr(inode, attr);

- if (IS_NOEXEC(inode) && !S_ISDIR(inode->i_mode))
- inode->i_mode &= S_IFMT | S_IRUGO | S_IWUGO;
- else
+ if (S_ISDIR(inode->i_mode))
inode->i_mode |= S_IXUGO;

inode->i_mode = ((inode->i_mode & S_IFMT) | ((((inode->i_mode & S_IRWXU
diff -urN S5-pre4/fs/hfs/inode.c S5-pre4-noexe/fs/hfs/inode.c
--- S5-pre4/fs/hfs/inode.c Fri Feb 16 22:55:36 2001
+++ S5-pre4-noexe/fs/hfs/inode.c Sun May 20 12:49:15 2001
@@ -38,7 +38,7 @@
struct hfs_fork *fk;
struct hfs_cat_entry *entry = HFS_I(inode)->entry;

- if (!IS_NOEXEC(inode) && (fork == HFS_FK_DATA)) {
+ if (fork == HFS_FK_DATA) {
inode->i_mode = S_IRWXUGO | S_IFREG;
} else {
inode->i_mode = S_IRUGO | S_IWUGO | S_IFREG;
diff -urN S5-pre4/fs/namei.c S5-pre4-noexe/fs/namei.c
--- S5-pre4/fs/namei.c Sat May 19 22:46:35 2001
+++ S5-pre4-noexe/fs/namei.c Sun May 20 12:48:17 2001
@@ -1051,7 +1051,7 @@
flag &= ~O_TRUNC;
} else if (S_ISBLK(inode->i_mode) || S_ISCHR(inode->i_mode)) {
error = -EACCES;
- if (IS_NODEV(inode))
+ if (nd->mnt->mnt_flags & MNT_NODEV)
goto exit;

flag &= ~O_TRUNC;
diff -urN S5-pre4/fs/super.c S5-pre4-noexe/fs/super.c
--- S5-pre4/fs/super.c Sat May 19 22:46:35 2001
+++ S5-pre4-noexe/fs/super.c Sun May 20 13:12:31 2001
@@ -55,7 +55,7 @@
extern int root_mountflags;

static int do_remount_sb(struct super_block *sb, int flags, char * data);
-static int do_remount(const char *dir, int flags, char * data);
+static int do_remount(const char *dir, int flags, int mnt_flags, char * data);

/* this is initialized in init/main.c */
kdev_t ROOT_DEV;
@@ -307,7 +307,8 @@

static struct vfsmount *add_vfsmnt(struct nameidata *nd,
struct dentry *root,
- const char *dev_name)
+ const char *dev_name,
+ int mnt_flags)
{
struct vfsmount *mnt;
struct super_block *sb = root->d_inode->i_sb;
@@ -318,8 +319,9 @@
goto out;
memset(mnt, 0, sizeof(struct vfsmount));

+ mnt->mnt_flags = mnt_flags;
if (nd || dev_name)
- mnt->mnt_flags = MNT_VISIBLE;
+ mnt->mnt_flags |= MNT_VISIBLE;

/* It may be NULL, but who cares? */
if (dev_name) {
@@ -460,16 +462,17 @@
int flag;
char *str;
} fs_info[] = {
- { MS_NOEXEC, ",noexec" },
- { MS_NOSUID, ",nosuid" },
- { MS_NODEV, ",nodev" },
{ MS_SYNCHRONOUS, ",sync" },
{ MS_MANDLOCK, ",mand" },
{ MS_NOATIME, ",noatime" },
{ MS_NODIRATIME, ",nodiratime" },
-#ifdef MS_NOSUB /* Can't find this except in mount.c */
- { MS_NOSUB, ",nosub" },
-#endif
+ { 0, NULL }
+};
+
+static struct proc_fs_info mnt_info[] = {
+ { MNT_NOSUID, ",nosuid" },
+ { MNT_NODEV, ",nodev" },
+ { MNT_NOEXEC, ",noexec" },
{ 0, NULL }
};

@@ -522,6 +525,10 @@
if (tmp->mnt_sb->s_flags & fs_infop->flag)
MANGLE(fs_infop->str);
}
+ for (fs_infop = mnt_info; fs_infop->flag; fs_infop++) {
+ if (tmp->mnt_flags & fs_infop->flag)
+ MANGLE(fs_infop->str);
+ }
if (!strcmp("nfs", tmp->mnt_sb->s_type->name)) {
nfss = &tmp->mnt_sb->u.nfs_sb.s_server;
len += sprintf(buf+len, ",v%d", nfss->rpc_ops->version);
@@ -786,7 +793,7 @@
if (!S_ISBLK(inode->i_mode))
goto out;
error = -EACCES;
- if (IS_NODEV(inode))
+ if (nd.mnt->mnt_flags & MNT_NODEV)
goto out;
bdev = inode->i_bdev;
bdops = devfs_get_ops ( devfs_get_handle_from_inode (inode) );
@@ -963,7 +970,7 @@
put_unnamed_dev(dev);
return ERR_PTR(-EINVAL);
}
- mnt = add_vfsmnt(NULL, sb->s_root, NULL);
+ mnt = add_vfsmnt(NULL, sb->s_root, NULL, 0);
if (!mnt) {
kill_super(sb, 0);
return ERR_PTR(-ENOMEM);
@@ -1014,7 +1021,7 @@
* we just try to remount it readonly.
*/
mntput(mnt);
- return do_remount("/", MS_RDONLY, NULL);
+ return do_remount("/", MS_RDONLY, 0, NULL);
}

spin_lock(&dcache_lock);
@@ -1155,11 +1162,11 @@
int err = 0;
if (!old_name || !*old_name)
return -EINVAL;
- if (path_init(old_name, LOOKUP_POSITIVE, &old_nd))
+ if (path_init(old_name, LOOKUP_POSITIVE|LOOKUP_FOLLOW, &old_nd))
err = path_walk(old_name, &old_nd);
if (err)
goto out;
- if (path_init(new_name, LOOKUP_POSITIVE, &new_nd))
+ if (path_init(new_name, LOOKUP_POSITIVE|LOOKUP_FOLLOW, &new_nd))
err = path_walk(new_name, &new_nd);
if (err)
goto out1;
@@ -1180,7 +1187,8 @@
down(&new_nd.dentry->d_inode->i_zombie);
if (IS_DEADDIR(new_nd.dentry->d_inode))
err = -ENOENT;
- else if (add_vfsmnt(&new_nd, old_nd.dentry, old_nd.mnt->mnt_devname))
+ else if (add_vfsmnt(&new_nd, old_nd.dentry, old_nd.mnt->mnt_devname,
+ old_nd.mnt->mnt_flags))
err = 0;
up(&new_nd.dentry->d_inode->i_zombie);
up(&mount_sem);
@@ -1200,7 +1208,7 @@
* on it - tough luck.
*/

-static int do_remount(const char *dir,int flags,char *data)
+static int do_remount(const char *dir,int flags,int mnt_flags,char *data)
{
struct nameidata nd;
int retval = 0;
@@ -1215,7 +1223,7 @@
retval = -ENODEV;
if (sb) {
retval = -EINVAL;
- if (nd.dentry == sb->s_root) {
+ if (nd.dentry == nd.mnt->mnt_root) {
/*
* Shrink the dcache and sync the device.
*/
@@ -1224,6 +1232,8 @@
if (flags & MS_RDONLY)
acct_auto_close(sb->s_dev);
retval = do_remount_sb(sb, flags, data);
+ if (!retval)
+ nd.mnt->mnt_flags=MNT_VISIBLE|mnt_flags;
}
}
path_release(&nd);
@@ -1286,6 +1296,7 @@
struct vfsmount *mnt = NULL;
struct super_block *sb;
int retval = 0;
+ int mnt_flags = 0;

/* Discard magic */
if ((flags & MS_MGC_MSK) == MS_MGC_VAL)
@@ -1298,11 +1309,20 @@
if (dev_name && !memchr(dev_name, 0, PAGE_SIZE))
return -EINVAL;

+ /* Separate the per-mountpoint flags */
+ if (flags & MS_NOSUID)
+ mnt_flags |= MNT_NOSUID;
+ if (flags & MS_NODEV)
+ mnt_flags |= MNT_NODEV;
+ if (flags & MS_NOEXEC)
+ mnt_flags |= MNT_NOEXEC;
+ flags &= ~(MS_NOSUID|MS_NOEXEC|MS_NODEV);
+
/* OK, looks good, now let's see what do they want */

/* just change the flags? - capabilities are checked in do_remount() */
if (flags & MS_REMOUNT)
- return do_remount(dir_name, flags & ~MS_REMOUNT,
+ return do_remount(dir_name, flags & ~MS_REMOUNT, mnt_flags,
(char *) data_page);

/* "mount --bind"? Equivalent to older "mount -t bind" */
@@ -1361,7 +1381,7 @@
down(&nd.dentry->d_inode->i_zombie);
if (!IS_DEADDIR(nd.dentry->d_inode)) {
retval = -ENOMEM;
- mnt = add_vfsmnt(&nd, sb->s_root, dev_name);
+ mnt = add_vfsmnt(&nd, sb->s_root, dev_name, mnt_flags);
}
up(&nd.dentry->d_inode->i_zombie);
if (!mnt)
@@ -1568,10 +1588,10 @@
devfs_mk_symlink (NULL, "root", DEVFS_FL_DEFAULT,
path + 5 + path_start, NULL, NULL);
memcpy (path + path_start, "/dev/", 5);
- vfsmnt = add_vfsmnt(NULL, sb->s_root, path + path_start);
+ vfsmnt = add_vfsmnt(NULL, sb->s_root, path + path_start, 0);
}
else
- vfsmnt = add_vfsmnt(NULL, sb->s_root, "/dev/root");
+ vfsmnt = add_vfsmnt(NULL, sb->s_root, "/dev/root", 0);
/* FIXME: if something will try to umount us right now... */
if (vfsmnt) {
set_fs_root(current->fs, vfsmnt, sb->s_root);
diff -urN S5-pre4/include/linux/fs.h S5-pre4-noexe/include/linux/fs.h
--- S5-pre4/include/linux/fs.h Sat May 19 22:46:36 2001
+++ S5-pre4-noexe/include/linux/fs.h Sun May 20 13:03:23 2001
@@ -116,10 +116,10 @@
#define MS_BIND 4096

/*
- * Flags that can be altered by MS_REMOUNT
+ * Superblock flags that can be altered by MS_REMOUNT
*/
-#define MS_RMT_MASK (MS_RDONLY|MS_NOSUID|MS_NODEV|MS_NOEXEC|\
- MS_SYNCHRONOUS|MS_MANDLOCK|MS_NOATIME|MS_NODIRATIME)
+#define MS_RMT_MASK (MS_RDONLY|MS_SYNCHRONOUS|MS_MANDLOCK|MS_NOATIME|\
+ MS_NODIRATIME)

/*
* Old magic mount flag and mask
@@ -152,9 +152,6 @@
#define __IS_FLG(inode,flg) ((inode)->i_sb->s_flags & (flg))

#define IS_RDONLY(inode) ((inode)->i_sb->s_flags & MS_RDONLY)
-#define IS_NOSUID(inode) __IS_FLG(inode, MS_NOSUID)
-#define IS_NODEV(inode) __IS_FLG(inode, MS_NODEV)
-#define IS_NOEXEC(inode) __IS_FLG(inode, MS_NOEXEC)
#define IS_SYNC(inode) (__IS_FLG(inode, MS_SYNCHRONOUS) || ((inode)->i_flags & S_SYNC))
#define IS_MANDLOCK(inode) __IS_FLG(inode, MS_MANDLOCK)

diff -urN S5-pre4/include/linux/mount.h S5-pre4-noexe/include/linux/mount.h
--- S5-pre4/include/linux/mount.h Fri Feb 16 18:33:56 2001
+++ S5-pre4-noexe/include/linux/mount.h Sun May 20 12:44:02 2001
@@ -12,7 +12,10 @@
#define _LINUX_MOUNT_H
#ifdef __KERNEL__

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

struct vfsmount
{
-
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