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From: David Howells <dhowells@redhat.com>
To: hch@lst.de
Cc: dhowells@redhat.com, linux-afs@lists.infradead.org,
	linux-kernel@vger.kernel.org
Subject: [PATCH 2/3] proc: Add a way to make network proc files writable
Date: Tue, 01 May 2018 00:20:33 +0100	[thread overview]
Message-ID: <152513043358.13808.4250608064312146536.stgit@warthog.procyon.org.uk> (raw)
In-Reply-To: <152513042072.13808.9692322366778075206.stgit@warthog.procyon.org.uk>

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>
---

 fs/proc/generic.c       |   24 ++++++++++++
 fs/proc/internal.h      |    2 +
 fs/proc/proc_net.c      |   92 +++++++++++++++++++++++++++++++++++++++++++++++
 include/linux/proc_fs.h |   12 ++++++
 4 files changed, 130 insertions(+)

diff --git a/fs/proc/generic.c b/fs/proc/generic.c
index 02bb1914f5f7..d0e5a68ae14a 100644
--- a/fs/proc/generic.c
+++ b/fs/proc/generic.c
@@ -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;
+}
diff --git a/fs/proc/internal.h b/fs/proc/internal.h
index 6d171485c45b..0f3eeed2767a 100644
--- a/fs/proc/internal.h
+++ b/fs/proc/internal.h
@@ -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;
 	unsigned int state_size;
 	void *data;
 	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
diff --git a/fs/proc/proc_net.c b/fs/proc/proc_net.c
index baf1994289ce..690764714fc3 100644
--- a/fs/proc/proc_net.c
+++ b/fs/proc/proc_net.c
@@ -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;
diff --git a/include/linux/proc_fs.h b/include/linux/proc_fs.h
index 928c7b2cbff4..33187c55eb8a 100644
--- a/include/linux/proc_fs.h
+++ b/include/linux/proc_fs.h
@@ -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 */
 

  parent reply	other threads:[~2018-04-30 23:20 UTC|newest]

Thread overview: 70+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-04-25 15:47 simplify procfs code for seq_file instances V2 Christoph Hellwig
2018-04-25 15:47 ` [PATCH 01/40] net/can: single_open_net needs to be paired with single_release_net Christoph Hellwig
2018-04-25 15:47 ` [PATCH 02/40] proc: simplify proc_register calling conventions Christoph Hellwig
2018-04-25 15:47 ` [PATCH 03/40] proc: add a proc_create_reg helper Christoph Hellwig
2018-04-25 15:47 ` [PATCH 04/40] proc: introduce proc_create_seq{,_data} Christoph Hellwig
2018-04-25 15:47 ` [PATCH 05/40] proc: introduce proc_create_seq_private Christoph Hellwig
2018-04-25 15:47 ` [PATCH 06/40] proc: introduce proc_create_single{,_data} Christoph Hellwig
2018-04-26  1:45   ` Finn Thain
2018-05-15 13:58     ` Christoph Hellwig
2018-04-25 15:47 ` [PATCH 07/40] ipv{4,6}/udp{,lite}: simplify proc registration Christoph Hellwig
2018-04-25 15:47 ` [PATCH 08/40] ipv{4,6}/tcp: simplify procfs registration Christoph Hellwig
2018-04-25 15:47 ` [PATCH 09/40] ipv{4,6}/ping: simplify proc file creation Christoph Hellwig
2018-04-25 15:47 ` [PATCH 10/40] ipv{4, 6}/raw: simplify ѕeq_file code Christoph Hellwig
2018-04-25 15:47 ` [PATCH 11/40] ipv6/flowlabel: simplify pid namespace lookup Christoph Hellwig
2018-05-05 12:37   ` Eric W. Biederman
2018-05-15 14:56     ` Christoph Hellwig
2018-05-17  5:28       ` Eric W. Biederman
2018-05-17  6:42         ` Christoph Hellwig
2018-05-17 19:14           ` Eric W. Biederman
2018-04-25 15:47 ` [PATCH 12/40] net/kcm: simplify proc registration Christoph Hellwig
2018-04-25 15:48 ` [PATCH 13/40] netfilter/x_tables: simplify ѕeq_file code Christoph Hellwig
2018-04-25 15:48 ` [PATCH 14/40] net: move seq_file_single_net to <linux/seq_file_net.h> Christoph Hellwig
2018-04-25 15:48 ` [PATCH 15/40] proc: introduce proc_create_net{,_data} Christoph Hellwig
2018-04-25 15:48 ` [PATCH 16/40] proc: introduce proc_create_net_single Christoph Hellwig
2018-04-25 15:48 ` [PATCH 17/40] acpi/battery: simplify procfs code Christoph Hellwig
2018-04-25 15:48 ` [PATCH 18/40] sgi-gru: " Christoph Hellwig
2018-04-25 15:48 ` [PATCH 19/40] megaraid: " Christoph Hellwig
2018-04-25 15:48 ` [PATCH 20/40] sg: " Christoph Hellwig
2018-04-25 15:48 ` [PATCH 21/40] afs: " Christoph Hellwig
2018-04-30 23:20   ` [PATCH 0/3] afs: Network-namespacing and proc David Howells
2018-04-30 23:20     ` [PATCH 1/3] afs: Rearrange fs/afs/proc.c David Howells
2018-05-15 13:43       ` Christoph Hellwig
2018-04-30 23:20     ` David Howells [this message]
2018-05-15 13:48       ` [PATCH 2/3] proc: Add a way to make network proc files writable Christoph Hellwig
2018-05-15 14:16       ` David Howells
2018-04-30 23:20     ` [PATCH 3/3] afs: Implement namespacing David Howells
2018-05-15 13:53       ` Christoph Hellwig
2018-05-15 14:28       ` 'Adding' a writable proc file under /proc/net/afs/ [was [PATCH 3/3] afs: Implement namespacing] David Howells
2018-04-25 15:48 ` [PATCH 22/40] ext4: simplify procfs code Christoph Hellwig
2018-04-25 15:48 ` [PATCH 23/40] jfs: " Christoph Hellwig
2018-04-25 15:48 ` [PATCH 24/40] staging/rtl8192u: " Christoph Hellwig
2018-04-25 15:48 ` [PATCH 25/40] resource: switch to proc_create_seq_data Christoph Hellwig
2018-04-25 15:48 ` [PATCH 26/40] drbd: switch to proc_create_single Christoph Hellwig
2018-04-25 15:48 ` [PATCH 27/40] rtc/proc: switch to proc_create_single_data Christoph Hellwig
2018-04-25 18:25   ` Alexandre Belloni
2018-04-25 15:48 ` [PATCH 28/40] bonding: switch to proc_create_seq_data Christoph Hellwig
2018-04-25 15:48 ` [PATCH 29/40] hostap: switch to proc_create_{seq,single}_data Christoph Hellwig
2018-04-25 15:48 ` [PATCH 30/40] neigh: switch to proc_create_seq_data Christoph Hellwig
2018-04-25 15:48 ` [PATCH 31/40] netfilter/xt_hashlimit: switch to proc_create_{seq, single}_data Christoph Hellwig
2018-04-25 15:48 ` [PATCH 32/40] netfilter/x_tables: switch to proc_create_seq_private Christoph Hellwig
2018-04-25 15:48 ` [PATCH 33/40] bluetooth: switch to proc_create_seq_data Christoph Hellwig
2018-04-25 15:48 ` [PATCH 34/40] atm: simplify procfs code Christoph Hellwig
2018-05-05 12:51   ` Eric W. Biederman
2018-05-15 14:12     ` Christoph Hellwig
2018-05-17  1:15       ` Eric W. Biederman
2018-04-25 15:48 ` [PATCH 35/40] atm: switch to proc_create_seq_private Christoph Hellwig
2018-04-25 15:48 ` [PATCH 36/40] isdn: replace ->proc_fops with ->proc_show Christoph Hellwig
2018-04-25 15:48 ` [PATCH 37/40] proc: don't detour through seq->private to get the inode Christoph Hellwig
2018-04-25 15:48 ` [PATCH 38/40] ide: remove ide_driver_proc_write Christoph Hellwig
2018-05-05 13:09   ` Eric W. Biederman
2018-04-25 15:48 ` [PATCH 39/40] ide: replace ->proc_fops with ->proc_show Christoph Hellwig
2018-04-25 15:48 ` [PATCH 40/40] tty: " Christoph Hellwig
2018-04-30 13:19 ` [PATCH 04/40] proc: introduce proc_create_seq{,_data} David Howells
2018-05-15 14:42   ` Christoph Hellwig
2018-04-30 15:38 ` simplify procfs code for seq_file instances V2 David Howells
2018-05-06 17:19 ` Alexey Dobriyan
2018-05-06 17:45   ` Al Viro
2018-05-09 16:53     ` Alexey Dobriyan
2018-05-15 14:03   ` Christoph Hellwig
2018-05-15 19:08 [PATCH 2/3] proc: Add a way to make network proc files writable Alexey Dobriyan

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