Commit 564def71 authored by David Howells's avatar David Howells
Browse files

proc: Add a way to make network proc files writable 



Provide two extra functions, proc_create_net_data_write() and
proc_create_net_single_write() that act like their non-write versions but
also set a write method in the proc_dir_entry struct.

An internal simple write function is provided that will copy its buffer and
hand it to the pde->write() method if available (or give an error if not).
The buffer may be modified by the write method.

Signed-off-by: default avatarDavid Howells <dhowells@redhat.com>
parent 5d9de25d

fs/proc/generic.c

+24 −0
Original line number Diff line number Diff line
@@ -741,3 +741,27 @@ void *PDE_DATA(const struct inode *inode) 
	return __PDE_DATA(inode);

}

EXPORT_SYMBOL(PDE_DATA);



/*

 * Pull a user buffer into memory and pass it to the file's write handler if

 * one is supplied.  The ->write() method is permitted to modify the

 * kernel-side buffer.

 */

ssize_t proc_simple_write(struct file *f, const char __user *ubuf, size_t size,

			  loff_t *_pos)

{

	struct proc_dir_entry *pde = PDE(file_inode(f));

	char *buf;

	int ret;



	if (!pde->write)

		return -EACCES;

	if (size == 0 || size > PAGE_SIZE - 1)

		return -EINVAL;

	buf = memdup_user_nul(ubuf, size);

	if (IS_ERR(buf))

		return PTR_ERR(buf);

	ret = pde->write(f, buf, size);

	kfree(buf);

	return ret == 0 ? size : ret;

}

fs/proc/internal.h

+2 −0
Original line number Diff line number Diff line
@@ -48,6 +48,7 @@ struct proc_dir_entry { 
		const struct seq_operations *seq_ops;

		int (*single_show)(struct seq_file *, void *);

	};

	proc_write_t write;

	void *data;

	unsigned int state_size;

	unsigned int low_ino;
@@ -187,6 +188,7 @@ static inline bool is_empty_pde(const struct proc_dir_entry *pde) 
{

	return S_ISDIR(pde->mode) && !pde->proc_iops;

}

extern ssize_t proc_simple_write(struct file *, const char __user *, size_t, loff_t *);



/*

 * inode.c

fs/proc/proc_net.c

+92 −0
Original line number Diff line number Diff line
@@ -46,6 +46,9 @@ static int seq_open_net(struct inode *inode, struct file *file) 


	WARN_ON_ONCE(state_size < sizeof(*p));



	if (file->f_mode & FMODE_WRITE && !PDE(inode)->write)

		return -EACCES;



	net = get_proc_net(inode);

	if (!net)

		return -ENXIO;
@@ -73,6 +76,7 @@ static int seq_release_net(struct inode *ino, struct file *f) 
static const struct file_operations proc_net_seq_fops = {

	.open		= seq_open_net,

	.read		= seq_read,

	.write		= proc_simple_write,

	.llseek		= seq_lseek,

	.release	= seq_release_net,

};
@@ -93,6 +97,50 @@ struct proc_dir_entry *proc_create_net_data(const char *name, umode_t mode, 
}

EXPORT_SYMBOL_GPL(proc_create_net_data);



/**

 * proc_create_net_data_write - Create a writable net_ns-specific proc file

 * @name: The name of the file.

 * @mode: The file's access mode.

 * @parent: The parent directory in which to create.

 * @ops: The seq_file ops with which to read the file.

 * @write: The write method which which to 'modify' the file.

 * @data: Data for retrieval by PDE_DATA().

 *

 * Create a network namespaced proc file in the @parent directory with the

 * specified @name and @mode that allows reading of a file that displays a

 * series of elements and also provides for the file accepting writes that have

 * some arbitrary effect.

 *

 * The functions in the @ops table are used to iterate over items to be

 * presented and extract the readable content using the seq_file interface.

 *

 * The @write function is called with the data copied into a kernel space

 * scratch buffer and has a NUL appended for convenience.  The buffer may be

 * modified by the @write function.  @write should return 0 on success.

 *

 * The @data value is accessible from the @show and @write functions by calling

 * PDE_DATA() on the file inode.  The network namespace must be accessed by

 * calling seq_file_net() on the seq_file struct.

 */

struct proc_dir_entry *proc_create_net_data_write(const char *name, umode_t mode,

						  struct proc_dir_entry *parent,

						  const struct seq_operations *ops,

						  proc_write_t write,

						  unsigned int state_size, void *data)

{

	struct proc_dir_entry *p;



	p = proc_create_reg(name, mode, &parent, data);

	if (!p)

		return NULL;

	p->proc_fops = &proc_net_seq_fops;

	p->seq_ops = ops;

	p->state_size = state_size;

	p->write = write;

	return proc_register(parent, p);

}

EXPORT_SYMBOL_GPL(proc_create_net_data_write);



static int single_open_net(struct inode *inode, struct file *file)

{

	struct proc_dir_entry *de = PDE(inode);
@@ -119,6 +167,7 @@ static int single_release_net(struct inode *ino, struct file *f) 
static const struct file_operations proc_net_single_fops = {

	.open		= single_open_net,

	.read		= seq_read,

	.write		= proc_simple_write,

	.llseek		= seq_lseek,

	.release	= single_release_net,

};
@@ -138,6 +187,49 @@ struct proc_dir_entry *proc_create_net_single(const char *name, umode_t mode, 
}

EXPORT_SYMBOL_GPL(proc_create_net_single);



/**

 * proc_create_net_single_write - Create a writable net_ns-specific proc file

 * @name: The name of the file.

 * @mode: The file's access mode.

 * @parent: The parent directory in which to create.

 * @show: The seqfile show method with which to read the file.

 * @write: The write method which which to 'modify' the file.

 * @data: Data for retrieval by PDE_DATA().

 *

 * Create a network-namespaced proc file in the @parent directory with the

 * specified @name and @mode that allows reading of a file that displays a

 * single element rather than a series and also provides for the file accepting

 * writes that have some arbitrary effect.

 *

 * The @show function is called to extract the readable content via the

 * seq_file interface.

 *

 * The @write function is called with the data copied into a kernel space

 * scratch buffer and has a NUL appended for convenience.  The buffer may be

 * modified by the @write function.  @write should return 0 on success.

 *

 * The @data value is accessible from the @show and @write functions by calling

 * PDE_DATA() on the file inode.  The network namespace must be accessed by

 * calling seq_file_single_net() on the seq_file struct.

 */

struct proc_dir_entry *proc_create_net_single_write(const char *name, umode_t mode,

						    struct proc_dir_entry *parent,

						    int (*show)(struct seq_file *, void *),

						    proc_write_t write,

						    void *data)

{

	struct proc_dir_entry *p;



	p = proc_create_reg(name, mode, &parent, data);

	if (!p)

		return NULL;

	p->proc_fops = &proc_net_single_fops;

	p->single_show = show;

	p->write = write;

	return proc_register(parent, p);

}

EXPORT_SYMBOL_GPL(proc_create_net_single_write);



static struct net *get_proc_task_net(struct inode *dir)

{

	struct task_struct *task;

include/linux/proc_fs.h

+12 −0
Original line number Diff line number Diff line
@@ -14,6 +14,8 @@ struct seq_operations; 


#ifdef CONFIG_PROC_FS



typedef int (*proc_write_t)(struct file *, char *, size_t);



extern void proc_root_init(void);

extern void proc_flush_task(struct task_struct *);
@@ -61,6 +63,16 @@ struct proc_dir_entry *proc_create_net_data(const char *name, umode_t mode, 
struct proc_dir_entry *proc_create_net_single(const char *name, umode_t mode,

		struct proc_dir_entry *parent,

		int (*show)(struct seq_file *, void *), void *data);

struct proc_dir_entry *proc_create_net_data_write(const char *name, umode_t mode,

						  struct proc_dir_entry *parent,

						  const struct seq_operations *ops,

						  proc_write_t write,

						  unsigned int state_size, void *data);

struct proc_dir_entry *proc_create_net_single_write(const char *name, umode_t mode,

						    struct proc_dir_entry *parent,

						    int (*show)(struct seq_file *, void *),

						    proc_write_t write,

						    void *data);



#else /* CONFIG_PROC_FS */

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