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overlayfs: Make f_path always point to the overlay and f_inode to the underlay

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Make file->f_path always point to the overlay dentry so that the path in
/proc/pid/fd is correct and to ensure that label-based LSMs have access to the
overlay as well as the underlay (path-based LSMs probably don't need it).

Using my union testsuite to set things up, before the patch I see:

	[root@andromeda union-testsuite]# bash 5</mnt/a/foo107
	[root@andromeda union-testsuite]# ls -l /proc/$$/fd/
	...
	lr-x------. 1 root root 64 Jun  5 14:38 5 -> /a/foo107
	[root@andromeda union-testsuite]# stat /mnt/a/foo107
	...
	Device: 23h/35d Inode: 13381       Links: 1
	...
	[root@andromeda union-testsuite]# stat -L /proc/$$/fd/5
	...
	Device: 23h/35d Inode: 13381       Links: 1
	...

After the patch:

	[root@andromeda union-testsuite]# bash 5</mnt/a/foo107
	[root@andromeda union-testsuite]# ls -l /proc/$$/fd/
	...
	lr-x------. 1 root root 64 Jun  5 14:22 5 -> /mnt/a/foo107
	[root@andromeda union-testsuite]# stat /mnt/a/foo107
	...
	Device: 23h/35d Inode: 40346       Links: 1
	...
	[root@andromeda union-testsuite]# stat -L /proc/$$/fd/5
	...
	Device: 23h/35d Inode: 40346       Links: 1
	...

Note the change in where /proc/$$/fd/5 points to in the ls command.  It was
pointing to /a/foo107 (which doesn't exist) and now points to /mnt/a/foo107
(which is correct).

The inode accessed, however, is the lower layer.  The union layer is on device
25h/37d and the upper layer on 24h/36d.

Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
David Howells 2015-06-18 14:32:31 +01:00 committed by Al Viro
parent f25801ee46
commit 4bacc9c923
8 changed files with 41 additions and 34 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

5
fs/dcache.c
View File

@ -1673,7 +1673,8 @@ void d_set_d_op(struct dentry *dentry, const struct dentry_operations *op)
DCACHE_OP_COMPARE |
DCACHE_OP_REVALIDATE |
DCACHE_OP_WEAK_REVALIDATE |
DCACHE_OP_DELETE ));
DCACHE_OP_DELETE |
DCACHE_OP_SELECT_INODE));
dentry->d_op = op;
if (!op)
return;
@ -1689,6 +1690,8 @@ void d_set_d_op(struct dentry *dentry, const struct dentry_operations *op)
dentry->d_flags |= DCACHE_OP_DELETE;
if (op->d_prune)
dentry->d_flags |= DCACHE_OP_PRUNE;
if (op->d_select_inode)
dentry->d_flags |= DCACHE_OP_SELECT_INODE;
}
EXPORT_SYMBOL(d_set_d_op);

1
fs/internal.h
View File

@ -107,6 +107,7 @@ extern struct file *do_file_open_root(struct dentry *, struct vfsmount *,
extern long do_handle_open(int mountdirfd,
struct file_handle __user *ufh, int open_flag);
extern int open_check_o_direct(struct file *f);
extern int vfs_open(const struct path *, struct file *, const struct cred *);
/*
* inode.c

49
fs/open.c
View File

@ -678,18 +678,18 @@ int open_check_o_direct(struct file *f)
}
static int do_dentry_open(struct file *f,
struct inode *inode,
int (*open)(struct inode *, struct file *),
const struct cred *cred)
{
static const struct file_operations empty_fops = {};
struct inode *inode;
int error;
f->f_mode = OPEN_FMODE(f->f_flags) | FMODE_LSEEK |
FMODE_PREAD | FMODE_PWRITE;
path_get(&f->f_path);
inode = f->f_inode = f->f_path.dentry->d_inode;
f->f_inode = inode;
f->f_mapping = inode->i_mapping;
if (unlikely(f->f_flags & O_PATH)) {
@ -793,7 +793,8 @@ int finish_open(struct file *file, struct dentry *dentry,
BUG_ON(*opened & FILE_OPENED); /* once it's opened, it's opened */
file->f_path.dentry = dentry;
error = do_dentry_open(file, open, current_cred());
error = do_dentry_open(file, d_backing_inode(dentry), open,
current_cred());
if (!error)
*opened |= FILE_OPENED;
@ -822,6 +823,28 @@ int finish_no_open(struct file *file, struct dentry *dentry)
}
EXPORT_SYMBOL(finish_no_open);
/**
* vfs_open - open the file at the given path
* @path: path to open
* @file: newly allocated file with f_flag initialized
* @cred: credentials to use
*/
int vfs_open(const struct path *path, struct file *file,
const struct cred *cred)
{
struct dentry *dentry = path->dentry;
struct inode *inode = dentry->d_inode;
file->f_path = *path;
if (dentry->d_flags & DCACHE_OP_SELECT_INODE) {
inode = dentry->d_op->d_select_inode(dentry, file->f_flags);
if (IS_ERR(inode))
return PTR_ERR(inode);
}
return do_dentry_open(file, inode, NULL, cred);
}
struct file *dentry_open(const struct path *path, int flags,
const struct cred *cred)
{
@ -853,26 +876,6 @@ struct file *dentry_open(const struct path *path, int flags,
}
EXPORT_SYMBOL(dentry_open);
/**
* vfs_open - open the file at the given path
* @path: path to open
* @filp: newly allocated file with f_flag initialized
* @cred: credentials to use
*/
int vfs_open(const struct path *path, struct file *filp,
const struct cred *cred)
{
struct inode *inode = path->dentry->d_inode;
if (inode->i_op->dentry_open)
return inode->i_op->dentry_open(path->dentry, filp, cred);
else {
filp->f_path = *path;
return do_dentry_open(filp, NULL, cred);
}
}
EXPORT_SYMBOL(vfs_open);
static inline int build_open_flags(int flags, umode_t mode, struct open_flags *op)
{
int lookup_flags = 0;

14
fs/overlayfs/inode.c
View File

@ -337,31 +337,30 @@ static bool ovl_open_need_copy_up(int flags, enum ovl_path_type type,
return true;
}
static int ovl_dentry_open(struct dentry *dentry, struct file *file,
const struct cred *cred)
struct inode *ovl_d_select_inode(struct dentry *dentry, unsigned file_flags)
{
int err;
struct path realpath;
enum ovl_path_type type;
type = ovl_path_real(dentry, &realpath);
if (ovl_open_need_copy_up(file->f_flags, type, realpath.dentry)) {
if (ovl_open_need_copy_up(file_flags, type, realpath.dentry)) {
err = ovl_want_write(dentry);
if (err)
return err;
return ERR_PTR(err);
if (file->f_flags & O_TRUNC)
if (file_flags & O_TRUNC)
err = ovl_copy_up_last(dentry, NULL, true);
else
err = ovl_copy_up(dentry);
ovl_drop_write(dentry);
if (err)
return err;
return ERR_PTR(err);
ovl_path_upper(dentry, &realpath);
}
return vfs_open(&realpath, file, cred);
return d_backing_inode(realpath.dentry);
}
static const struct inode_operations ovl_file_inode_operations = {
@ -372,7 +371,6 @@ static const struct inode_operations ovl_file_inode_operations = {
.getxattr = ovl_getxattr,
.listxattr = ovl_listxattr,
.removexattr = ovl_removexattr,
.dentry_open = ovl_dentry_open,
};
static const struct inode_operations ovl_symlink_inode_operations = {

1
fs/overlayfs/overlayfs.h
View File

@ -173,6 +173,7 @@ ssize_t ovl_getxattr(struct dentry *dentry, const char *name,
void *value, size_t size);
ssize_t ovl_listxattr(struct dentry *dentry, char *list, size_t size);
int ovl_removexattr(struct dentry *dentry, const char *name);
struct inode *ovl_d_select_inode(struct dentry *dentry, unsigned file_flags);
struct inode *ovl_new_inode(struct super_block *sb, umode_t mode,
struct ovl_entry *oe);

1
fs/overlayfs/super.c
View File

@ -275,6 +275,7 @@ static void ovl_dentry_release(struct dentry *dentry)
static const struct dentry_operations ovl_dentry_operations = {
.d_release = ovl_dentry_release,
.d_select_inode = ovl_d_select_inode,
};
static struct ovl_entry *ovl_alloc_entry(unsigned int numlower)

2
include/linux/dcache.h
View File

@ -160,6 +160,7 @@ struct dentry_operations {
char *(*d_dname)(struct dentry *, char *, int);
struct vfsmount *(*d_automount)(struct path *);
int (*d_manage)(struct dentry *, bool);
struct inode *(*d_select_inode)(struct dentry *, unsigned);
} ____cacheline_aligned;
/*
@ -225,6 +226,7 @@ struct dentry_operations {
#define DCACHE_MAY_FREE 0x00800000
#define DCACHE_FALLTHRU 0x01000000 /* Fall through to lower layer */
#define DCACHE_OP_SELECT_INODE 0x02000000 /* Unioned entry: dcache op selects inode */
extern seqlock_t rename_lock;

2
include/linux/fs.h
View File

@ -1641,7 +1641,6 @@ struct inode_operations {
int (*set_acl)(struct inode *, struct posix_acl *, int);
/* WARNING: probably going away soon, do not use! */
int (*dentry_open)(struct dentry *, struct file *, const struct cred *);
} ____cacheline_aligned;
ssize_t rw_copy_check_uvector(int type, const struct iovec __user * uvector,
@ -2194,7 +2193,6 @@ extern struct file *file_open_name(struct filename *, int, umode_t);
extern struct file *filp_open(const char *, int, umode_t);
extern struct file *file_open_root(struct dentry *, struct vfsmount *,
const char *, int);
extern int vfs_open(const struct path *, struct file *, const struct cred *);
extern struct file * dentry_open(const struct path *, int, const struct cred *);
extern int filp_close(struct file *, fl_owner_t id);