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authorNicolai Stange <nicstange@gmail.com>2016-03-22 14:11:15 +0100
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2016-04-12 23:14:21 +0200
commitc64688081490321f2d23a292ef24e60bb321f3f1 (patch)
treea2fb5072922a286d0161b9125ca7c04ecf79fa0b /fs/debugfs
parentdebugfs: prevent access to removed files' private data (diff)
downloadlinux-c64688081490321f2d23a292ef24e60bb321f3f1.tar.xz
linux-c64688081490321f2d23a292ef24e60bb321f3f1.zip
debugfs: add support for self-protecting attribute file fops
In order to protect them against file removal issues, debugfs_create_file() creates a lifetime managing proxy around each struct file_operations handed in. In cases where this struct file_operations is able to manage file lifetime by itself already, the proxy created by debugfs is a waste of resources. The most common class of struct file_operations given to debugfs are those defined by means of the DEFINE_SIMPLE_ATTRIBUTE() macro. Introduce a DEFINE_DEBUGFS_ATTRIBUTE() macro to allow any struct file_operations of this class to be easily made file lifetime aware and thus, to be operated unproxied. Specifically, introduce debugfs_attr_read() and debugfs_attr_write() which wrap simple_attr_read() and simple_attr_write() under the protection of a debugfs_use_file_start()/debugfs_use_file_finish() pair. Make DEFINE_DEBUGFS_ATTRIBUTE() set the defined struct file_operations' ->read() and ->write() members to these wrappers. Export debugfs_create_file_unsafe() in order to allow debugfs users to create their files in non-proxying operation mode. Signed-off-by: Nicolai Stange <nicstange@gmail.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'fs/debugfs')
-rw-r--r--fs/debugfs/file.c28
-rw-r--r--fs/debugfs/inode.c28
2 files changed, 56 insertions, 0 deletions
diff --git a/fs/debugfs/file.c b/fs/debugfs/file.c
index 6eb58a8ed03c..8ef56d9499a4 100644
--- a/fs/debugfs/file.c
+++ b/fs/debugfs/file.c
@@ -284,6 +284,34 @@ const struct file_operations debugfs_full_proxy_file_operations = {
.open = full_proxy_open,
};
+ssize_t debugfs_attr_read(struct file *file, char __user *buf,
+ size_t len, loff_t *ppos)
+{
+ ssize_t ret;
+ int srcu_idx;
+
+ ret = debugfs_use_file_start(F_DENTRY(file), &srcu_idx);
+ if (likely(!ret))
+ ret = simple_attr_read(file, buf, len, ppos);
+ debugfs_use_file_finish(srcu_idx);
+ return ret;
+}
+EXPORT_SYMBOL_GPL(debugfs_attr_read);
+
+ssize_t debugfs_attr_write(struct file *file, const char __user *buf,
+ size_t len, loff_t *ppos)
+{
+ ssize_t ret;
+ int srcu_idx;
+
+ ret = debugfs_use_file_start(F_DENTRY(file), &srcu_idx);
+ if (likely(!ret))
+ ret = simple_attr_write(file, buf, len, ppos);
+ debugfs_use_file_finish(srcu_idx);
+ return ret;
+}
+EXPORT_SYMBOL_GPL(debugfs_attr_write);
+
static struct dentry *debugfs_create_mode(const char *name, umode_t mode,
struct dentry *parent, void *value,
const struct file_operations *fops,
diff --git a/fs/debugfs/inode.c b/fs/debugfs/inode.c
index 136f269f01de..41e079a8da26 100644
--- a/fs/debugfs/inode.c
+++ b/fs/debugfs/inode.c
@@ -369,6 +369,33 @@ struct dentry *debugfs_create_file(const char *name, umode_t mode,
}
EXPORT_SYMBOL_GPL(debugfs_create_file);
+/**
+ * debugfs_create_file_unsafe - create a file in the debugfs filesystem
+ * @name: a pointer to a string containing the name of the file to create.
+ * @mode: the permission that the file should have.
+ * @parent: a pointer to the parent dentry for this file. This should be a
+ * directory dentry if set. If this parameter is NULL, then the
+ * file will be created in the root of the debugfs filesystem.
+ * @data: a pointer to something that the caller will want to get to later
+ * on. The inode.i_private pointer will point to this value on
+ * the open() call.
+ * @fops: a pointer to a struct file_operations that should be used for
+ * this file.
+ *
+ * debugfs_create_file_unsafe() is completely analogous to
+ * debugfs_create_file(), the only difference being that the fops
+ * handed it will not get protected against file removals by the
+ * debugfs core.
+ *
+ * It is your responsibility to protect your struct file_operation
+ * methods against file removals by means of debugfs_use_file_start()
+ * and debugfs_use_file_finish(). ->open() is still protected by
+ * debugfs though.
+ *
+ * Any struct file_operations defined by means of
+ * DEFINE_DEBUGFS_ATTRIBUTE() is protected against file removals and
+ * thus, may be used here.
+ */
struct dentry *debugfs_create_file_unsafe(const char *name, umode_t mode,
struct dentry *parent, void *data,
const struct file_operations *fops)
@@ -379,6 +406,7 @@ struct dentry *debugfs_create_file_unsafe(const char *name, umode_t mode,
&debugfs_noop_file_operations,
fops);
}
+EXPORT_SYMBOL_GPL(debugfs_create_file_unsafe);
/**
* debugfs_create_file_size - create a file in the debugfs filesystem