Re: [PATCH] Possible race in sysfs_read_file() and sysfs_write_file()

[Andrew Morton <akpm@osdl.org>]

Simon Derr <Simon.Derr@bull.net> wrote:
>
> I think there is a possibility for two threads from a single process to
> race in sysfs_read_file() if they call read() on the same file at the same
> time.

I think there is, too.

I also wonder what happens if the first read of a sysfs file is not at
offset zero (eg: pread()):

static ssize_t
sysfs_read_file(struct file *file, char __user *buf, size_t count, loff_t *ppos)
{
	struct sysfs_buffer * buffer = file->private_data;
	ssize_t retval = 0;

	if (!*ppos) {
		if ((retval = fill_read_buffer(file->f_dentry,buffer)))


we seem to not allocate the buffer at all?