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Commit 4bacc9c9 authored by David Howells's avatar David Howells Committed by Al Viro
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overlayfs: Make f_path always point to the overlay and f_inode to the underlay 



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: default avatarDavid Howells <dhowells@redhat.com>
Signed-off-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
parent f25801ee

fs/dcache.c

+4 −1
Original line number Diff line number Diff line
@@ -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);

fs/internal.h

+1 −0
Original line number Diff line number Diff line
@@ -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

fs/open.c

+26 −23
Original line number Diff line number Diff line
@@ -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;

fs/overlayfs/inode.c

+6 −8
Original line number Diff line number Diff line
@@ -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 = {

fs/overlayfs/overlayfs.h

+1 −0
Original line number Diff line number Diff line
@@ -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);