On Tue, Sep 18, 2012 at 01:24:15PM -0700, David Rientjes wrote:
> On Tue, 18 Sep 2012, Konrad Rzeszutek Wilk wrote:
>
> > diff --git a/fs/debugfs/file.c b/fs/debugfs/file.c
> > index 2340f69..309b235 100644
> > --- a/fs/debugfs/file.c
> > +++ b/fs/debugfs/file.c
> > @@ -524,6 +524,7 @@ EXPORT_SYMBOL_GPL(debugfs_create_blob);
> > struct array_data {
> > void *array;
> > u32 elements;
> > + struct mutex lock;
>
> This should be a spinlock.
I would get warnings about using a spinlock..
.. snip..
> > + mutex_unlock(&data->lock);
> > return simple_read_from_buffer(buf, len, ppos,
> > file->private_data, size);
> > }
>
> Your critical section isn't entirely covered since you're still accessing
> file->private_data in the call to simple_read_from_buffer(). What happens
> if a concurrent reader does file->private_data = NULL immediately after
> your unlock?
Duh!
diff --git a/fs/debugfs/file.c b/fs/debugfs/file.c
index 2340f69..c6d9088 100644
--- a/fs/debugfs/file.c
+++ b/fs/debugfs/file.c
@@ -524,6 +524,7 @@ EXPORT_SYMBOL_GPL(debugfs_create_blob);
struct array_data {
void *array;
u32 elements;
+ struct mutex lock;
};
static int u32_array_open(struct inode *inode, struct file *file)
@@ -580,6 +581,7 @@ static ssize_t u32_array_read(struct file *file, char
__user *buf, size_t len,
struct array_data *data = inode->i_private;
size_t size;
+ mutex_lock(&data->lock);
if (*ppos == 0) {
if (file->private_data) {
kfree(file->private_data);
@@ -594,8 +596,10 @@ static ssize_t u32_array_read(struct file *file, char
__user *buf, size_t len,
if (file->private_data)
size = strlen(file->private_data);
- return simple_read_from_buffer(buf, len, ppos,
+ size = simple_read_from_buffer(buf, len, ppos,
file->private_data, size);
+ mutex_unlock(&data->lock);
+ return size;
}
static int u32_array_release(struct inode *inode, struct file *file)
@@ -643,6 +647,7 @@ struct dentry *debugfs_create_u32_array(const char *name,
umode_t mode,
data->array = array;
data->elements = elements;
+ mutex_init(&data->lock);
return debugfs_create_file(name, mode, parent, data, &u32_array_fops);
}
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