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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: David Howells <dhowells@redhat.com>
This commit is contained in:
David Howells 2018-05-18 11:46:15 +01:00
parent 5d9de25d93
commit 564def7176
4 changed files with 130 additions and 0 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

24
fs/proc/generic.c
View File

@ -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;
}

2
fs/proc/internal.h
View File

@ -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

92
fs/proc/proc_net.c
View File

@ -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;

12
include/linux/proc_fs.h
View File

@ -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 */