[patch 01/10] vfs: add path_create() and path_mknod()

From: Miklos Szeredi
Date: Wed Apr 02 2008 - 16:17:44 EST

From: Miklos Szeredi <mszeredi@xxxxxxx>

R/o bind mounts require operations which modify the filesystem to be
wrapped in mnt_want_write()/mnt_drop_write(). Create helpers which do
this, so callers won't need to bother, and more importantly, cannot
forget! Call these path_*, analogous to vfs_*. Where there are no
callers of vfs_* left, make them static.

This series is a cleanup, as well as fixing several places (mostly in
nfsd) where mnt_{want,drop}_write() were missing.

It will also help with merging You Know What(*) security module, which
needs to know the path within the namespace, and not just within the
filesystem. These helpers will allow the security hooks to be in a
common place, and need not be repeated in all callers.

(*) AppArmor is a swear word in VFS circles, for some reason or other.

This patch:

Introduce path_create() and path_mknod(). Make vfs_create() and
vfs_mknod() static.

Signed-off-by: Miklos Szeredi <mszeredi@xxxxxxx>
---
fs/ecryptfs/inode.c | 21 +++++++-------
fs/namei.c | 75 +++++++++++++++++++++++++++-------------------------
fs/nfsd/vfs.c | 19 ++++++-------
include/linux/fs.h | 4 +-
ipc/mqueue.c | 6 +++-
net/unix/af_unix.c | 6 ----
6 files changed, 68 insertions(+), 63 deletions(-)

Index: vfs-2.6/fs/namei.c
===================================================================
--- vfs-2.6.orig/fs/namei.c 2008-04-02 21:10:14.000000000 +0200
+++ vfs-2.6/fs/namei.c 2008-04-02 21:10:17.000000000 +0200
@@ -1574,7 +1574,7 @@ void unlock_rename(struct dentry *p1, st
}
}

-int vfs_create(struct inode *dir, struct dentry *dentry, int mode,
+static int vfs_create(struct inode *dir, struct dentry *dentry, int mode,
struct nameidata *nd)
{
int error = may_create(dir, dentry, nd);
@@ -1596,6 +1596,20 @@ int vfs_create(struct inode *dir, struct
return error;
}

+int path_create(struct path *dir_path, struct dentry *dentry, int mode,
+ struct nameidata *nd)
+{
+ int error = mnt_want_write(dir_path->mnt);
+
+ if (!error) {
+ error = vfs_create(dir_path->dentry->d_inode, dentry, mode, nd);
+ mnt_drop_write(dir_path->mnt);
+ }
+
+ return error;
+}
+EXPORT_SYMBOL(path_create);
+
int may_open(struct nameidata *nd, int acc_mode, int flag)
{
struct dentry *dentry = nd->path.dentry;
@@ -2015,7 +2029,7 @@ fail:
}
EXPORT_SYMBOL_GPL(lookup_create);

-int vfs_mknod(struct inode *dir, struct dentry *dentry, int mode, dev_t dev)
+static int vfs_mknod(struct inode *dir, struct dentry *dentry, int mode, dev_t dev)
{
int error = may_create(dir, dentry, NULL);

@@ -2039,22 +2053,19 @@ int vfs_mknod(struct inode *dir, struct
return error;
}

-static int may_mknod(mode_t mode)
+int path_mknod(struct path *dir_path, struct dentry *dentry, int mode,
+ dev_t dev)
{
- switch (mode & S_IFMT) {
- case S_IFREG:
- case S_IFCHR:
- case S_IFBLK:
- case S_IFIFO:
- case S_IFSOCK:
- case 0: /* zero mode translates to S_IFREG */
- return 0;
- case S_IFDIR:
- return -EPERM;
- default:
- return -EINVAL;
+ int error = mnt_want_write(dir_path->mnt);
+
+ if (!error) {
+ error = vfs_mknod(dir_path->dentry->d_inode, dentry, mode, dev);
+ mnt_drop_write(dir_path->mnt);
}
+
+ return error;
}
+EXPORT_SYMBOL(path_mknod);

asmlinkage long sys_mknodat(int dfd, const char __user *filename, int mode,
unsigned dev)
@@ -2080,26 +2091,22 @@ asmlinkage long sys_mknodat(int dfd, con
}
if (!IS_POSIXACL(nd.path.dentry->d_inode))
mode &= ~current->fs->umask;
- error = may_mknod(mode);
- if (error)
- goto out_dput;
- error = mnt_want_write(nd.path.mnt);
- if (error)
- goto out_dput;
switch (mode & S_IFMT) {
- case 0: case S_IFREG:
- error = vfs_create(nd.path.dentry->d_inode,dentry,mode,&nd);
- break;
- case S_IFCHR: case S_IFBLK:
- error = vfs_mknod(nd.path.dentry->d_inode,dentry,mode,
- new_decode_dev(dev));
- break;
- case S_IFIFO: case S_IFSOCK:
- error = vfs_mknod(nd.path.dentry->d_inode,dentry,mode,0);
- break;
+ case 0: case S_IFREG:
+ error = path_create(&nd.path, dentry, mode, &nd);
+ break;
+ case S_IFCHR: case S_IFBLK:
+ error = path_mknod(&nd.path, dentry, mode, new_decode_dev(dev));
+ break;
+ case S_IFIFO: case S_IFSOCK:
+ error = path_mknod(&nd.path, dentry, mode, 0);
+ break;
+ case S_IFDIR:
+ error = -EPERM;
+ break;
+ default:
+ error = -EINVAL;
}
- mnt_drop_write(nd.path.mnt);
-out_dput:
dput(dentry);
out_unlock:
mutex_unlock(&nd.path.dentry->d_inode->i_mutex);
@@ -2966,11 +2973,9 @@ EXPORT_SYMBOL(permission);
EXPORT_SYMBOL(vfs_permission);
EXPORT_SYMBOL(file_permission);
EXPORT_SYMBOL(unlock_rename);
-EXPORT_SYMBOL(vfs_create);
EXPORT_SYMBOL(vfs_follow_link);
EXPORT_SYMBOL(vfs_link);
EXPORT_SYMBOL(vfs_mkdir);
-EXPORT_SYMBOL(vfs_mknod);
EXPORT_SYMBOL(generic_permission);
EXPORT_SYMBOL(vfs_readlink);
EXPORT_SYMBOL(vfs_rename);
Index: vfs-2.6/include/linux/fs.h
===================================================================
--- vfs-2.6.orig/include/linux/fs.h 2008-04-02 21:10:14.000000000 +0200
+++ vfs-2.6/include/linux/fs.h 2008-04-02 21:10:17.000000000 +0200
@@ -1123,9 +1123,9 @@ extern void unlock_super(struct super_bl
* VFS helper functions..
*/
extern int vfs_permission(struct nameidata *, int);
-extern int vfs_create(struct inode *, struct dentry *, int, struct nameidata *);
+extern int path_create(struct path *, struct dentry *, int, struct nameidata *);
extern int vfs_mkdir(struct inode *, struct dentry *, int);
-extern int vfs_mknod(struct inode *, struct dentry *, int, dev_t);
+extern int path_mknod(struct path *, struct dentry *, int, dev_t);
extern int vfs_symlink(struct inode *, struct dentry *, const char *, int);
extern int vfs_link(struct dentry *, struct inode *, struct dentry *);
extern int vfs_rmdir(struct inode *, struct dentry *);
Index: vfs-2.6/fs/ecryptfs/inode.c
===================================================================
--- vfs-2.6.orig/fs/ecryptfs/inode.c 2008-04-02 21:10:15.000000000 +0200
+++ vfs-2.6/fs/ecryptfs/inode.c 2008-04-02 21:10:17.000000000 +0200
@@ -67,7 +67,7 @@ static void unlock_dir(struct dentry *di
* Returns zero on success; non-zero on error condition
*/
static int
-ecryptfs_create_underlying_file(struct inode *lower_dir_inode,
+ecryptfs_create_underlying_file(struct dentry *lower_dir_dentry,
struct dentry *dentry, int mode,
struct nameidata *nd)
{
@@ -79,9 +79,9 @@ ecryptfs_create_underlying_file(struct i

dentry_save = nd->path.dentry;
vfsmount_save = nd->path.mnt;
- nd->path.dentry = lower_dentry;
+ nd->path.dentry = lower_dir_dentry;
nd->path.mnt = lower_mnt;
- rc = vfs_create(lower_dir_inode, lower_dentry, mode, nd);
+ rc = path_create(&nd->path, lower_dentry, mode, nd);
nd->path.dentry = dentry_save;
nd->path.mnt = vfsmount_save;
return rc;
@@ -117,7 +117,7 @@ ecryptfs_do_create(struct inode *directo
rc = PTR_ERR(lower_dir_dentry);
goto out;
}
- rc = ecryptfs_create_underlying_file(lower_dir_dentry->d_inode,
+ rc = ecryptfs_create_underlying_file(lower_dir_dentry,
ecryptfs_dentry, mode, nd);
if (rc) {
printk(KERN_ERR "%s: Failure to create dentry in lower fs; "
@@ -535,20 +535,21 @@ ecryptfs_mknod(struct inode *dir, struct
{
int rc;
struct dentry *lower_dentry;
- struct dentry *lower_dir_dentry;
+ struct path lower_dir;

lower_dentry = ecryptfs_dentry_to_lower(dentry);
- lower_dir_dentry = lock_parent(lower_dentry);
- rc = vfs_mknod(lower_dir_dentry->d_inode, lower_dentry, mode, dev);
+ lower_dir.mnt = ecryptfs_dentry_to_lower_mnt(dentry);
+ lower_dir.dentry = lock_parent(lower_dentry);
+ rc = path_mknod(&lower_dir, lower_dentry, mode, dev);
if (rc || !lower_dentry->d_inode)
goto out;
rc = ecryptfs_interpose(lower_dentry, dentry, dir->i_sb, 0);
if (rc)
goto out;
- fsstack_copy_attr_times(dir, lower_dir_dentry->d_inode);
- fsstack_copy_inode_size(dir, lower_dir_dentry->d_inode);
+ fsstack_copy_attr_times(dir, lower_dir.dentry->d_inode);
+ fsstack_copy_inode_size(dir, lower_dir.dentry->d_inode);
out:
- unlock_dir(lower_dir_dentry);
+ unlock_dir(lower_dir.dentry);
if (!dentry->d_inode)
d_drop(dentry);
return rc;
Index: vfs-2.6/fs/nfsd/vfs.c
===================================================================
--- vfs-2.6.orig/fs/nfsd/vfs.c 2008-04-02 21:10:14.000000000 +0200
+++ vfs-2.6/fs/nfsd/vfs.c 2008-04-02 21:10:17.000000000 +0200
@@ -1185,6 +1185,7 @@ nfsd_create(struct svc_rqst *rqstp, stru
char *fname, int flen, struct iattr *iap,
int type, dev_t rdev, struct svc_fh *resfhp)
{
+ struct path dir_path;
struct dentry *dentry, *dchild = NULL;
struct inode *dirp;
__be32 err;
@@ -1249,13 +1250,12 @@ nfsd_create(struct svc_rqst *rqstp, stru
iap->ia_mode = 0;
iap->ia_mode = (iap->ia_mode & S_IALLUGO) | type;

- /*
- * Get the dir op function pointer.
- */
+ dir_path.mnt = fhp->fh_export->ex_path.mnt;
+ dir_path.dentry = dentry;
err = 0;
switch (type) {
case S_IFREG:
- host_err = vfs_create(dirp, dchild, iap->ia_mode, NULL);
+ host_err = path_create(&dir_path, dchild, iap->ia_mode, NULL);
break;
case S_IFDIR:
host_err = vfs_mkdir(dirp, dchild, iap->ia_mode);
@@ -1264,11 +1264,7 @@ nfsd_create(struct svc_rqst *rqstp, stru
case S_IFBLK:
case S_IFIFO:
case S_IFSOCK:
- host_err = mnt_want_write(fhp->fh_export->ex_path.mnt);
- if (host_err)
- break;
- host_err = vfs_mknod(dirp, dchild, iap->ia_mode, rdev);
- mnt_drop_write(fhp->fh_export->ex_path.mnt);
+ host_err = path_mknod(&dir_path, dchild, iap->ia_mode, rdev);
break;
default:
printk("nfsd: bad file type %o in nfsd_create\n", type);
@@ -1311,6 +1307,7 @@ nfsd_create_v3(struct svc_rqst *rqstp, s
struct svc_fh *resfhp, int createmode, u32 *verifier,
int *truncp, int *created)
{
+ struct path dir_path;
struct dentry *dentry, *dchild = NULL;
struct inode *dirp;
__be32 err;
@@ -1397,7 +1394,9 @@ nfsd_create_v3(struct svc_rqst *rqstp, s
goto out;
}

- host_err = vfs_create(dirp, dchild, iap->ia_mode, NULL);
+ dir_path.mnt = fhp->fh_export->ex_path.mnt;
+ dir_path.dentry = dentry;
+ host_err = path_create(&dir_path, dchild, iap->ia_mode, NULL);
if (host_err < 0)
goto out_nfserr;
if (created)
Index: vfs-2.6/ipc/mqueue.c
===================================================================
--- vfs-2.6.orig/ipc/mqueue.c 2008-04-02 21:10:14.000000000 +0200
+++ vfs-2.6/ipc/mqueue.c 2008-04-02 21:10:17.000000000 +0200
@@ -599,6 +599,7 @@ static struct file *do_create(struct den
{
struct mq_attr attr;
struct file *result;
+ struct path dir_path;
int ret;

if (u_attr) {
@@ -616,7 +617,10 @@ static struct file *do_create(struct den
ret = mnt_want_write(mqueue_mnt);
if (ret)
goto out;
- ret = vfs_create(dir->d_inode, dentry, mode, NULL);
+
+ dir_path.mnt = mqueue_mnt;
+ dir_path.dentry = dir;
+ ret = path_create(&dir_path, dentry, mode, NULL);
dentry->d_fsdata = NULL;
if (ret)
goto out_drop_write;
Index: vfs-2.6/net/unix/af_unix.c
===================================================================
--- vfs-2.6.orig/net/unix/af_unix.c 2008-04-02 21:10:14.000000000 +0200
+++ vfs-2.6/net/unix/af_unix.c 2008-04-02 21:10:17.000000000 +0200
@@ -819,11 +819,7 @@ static int unix_bind(struct socket *sock
*/
mode = S_IFSOCK |
(SOCK_INODE(sock)->i_mode & ~current->fs->umask);
- err = mnt_want_write(nd.path.mnt);
- if (err)
- goto out_mknod_dput;
- err = vfs_mknod(nd.path.dentry->d_inode, dentry, mode, 0);
- mnt_drop_write(nd.path.mnt);
+ err = path_mknod(&nd.path, dentry, mode, 0);
if (err)
goto out_mknod_dput;
mutex_unlock(&nd.path.dentry->d_inode->i_mutex);

--
--
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