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usb: gadget: f_fs: buffer data from ‘oversized’ OUT requests 

f_fs rounds up read(2) requests to a multiple of a max packet size
which means that host may provide more data than user has space for.
So far, the excess data has been silently ignored.

This introduces a buffer for a tail of such requests so that they are
returned on next read instead of being ignored.

Signed-off-by: Michal Nazarewicz <mina86@mina86.com>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>
This commit is contained in:
Michal Nazarewicz 2016-05-21 20:47:35 +02:00 committed by Felipe Balbi
parent c662a31be7
commit 9353afbbfa
1 changed files with 109 additions and 21 deletions
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130
drivers/usb/gadget/function/f_fs.c
View File

@ -130,6 +130,12 @@ struct ffs_epfile {
struct dentry *dentry;
/*
* Buffer for holding data from partial reads which may happen since
* we’re rounding user read requests to a multiple of a max packet size.
*/
struct ffs_buffer *read_buffer; /* P: epfile->mutex */
char name[5];
unsigned char in; /* P: ffs->eps_lock */
@ -138,6 +144,12 @@ struct ffs_epfile {
unsigned char _pad;
};
struct ffs_buffer {
size_t length;
char *data;
char storage[];
};
/* ffs_io_data structure ***************************************************/
struct ffs_io_data {
@ -667,6 +679,11 @@ static ssize_t ffs_copy_to_iter(void *data, int data_len, struct iov_iter *iter)
* Was the buffer aligned in the first place, no such problem would
* happen.
*
* Data may be dropped only in AIO reads. Synchronous reads are handled
* by splitting a request into multiple parts. This splitting may still
* be a problem though so it’s likely best to align the buffer
* regardless of it being AIO or not..
*
* This only affects OUT endpoints, i.e. reading data with a read(2),
* aio_read(2) etc. system calls. Writing data to an IN endpoint is not
* affected.
@ -716,6 +733,56 @@ static void ffs_epfile_async_io_complete(struct usb_ep *_ep,
schedule_work(&io_data->work);
}
/* Assumes epfile->mutex is held. */
static ssize_t __ffs_epfile_read_buffered(struct ffs_epfile *epfile,
struct iov_iter *iter)
{
struct ffs_buffer *buf = epfile->read_buffer;
ssize_t ret;
if (!buf)
return 0;
ret = copy_to_iter(buf->data, buf->length, iter);
if (buf->length == ret) {
kfree(buf);
epfile->read_buffer = NULL;
} else if (unlikely(iov_iter_count(iter))) {
ret = -EFAULT;
} else {
buf->length -= ret;
buf->data += ret;
}
return ret;
}
/* Assumes epfile->mutex is held. */
static ssize_t __ffs_epfile_read_data(struct ffs_epfile *epfile,
void *data, int data_len,
struct iov_iter *iter)
{
struct ffs_buffer *buf;
ssize_t ret = copy_to_iter(data, data_len, iter);
if (likely(data_len == ret))
return ret;
if (unlikely(iov_iter_count(iter)))
return -EFAULT;
/* See ffs_copy_to_iter for more context. */
pr_warn("functionfs read size %d > requested size %zd, splitting request into multiple reads.",
data_len, ret);
data_len -= ret;
buf = kmalloc(sizeof(*buf) + data_len, GFP_KERNEL);
buf->length = data_len;
buf->data = buf->storage;
memcpy(buf->storage, data + ret, data_len);
epfile->read_buffer = buf;
return ret;
}
static ssize_t ffs_epfile_io(struct file *file, struct ffs_io_data *io_data)
{
struct ffs_epfile *epfile = file->private_data;
@ -745,21 +812,40 @@ static ssize_t ffs_epfile_io(struct file *file, struct ffs_io_data *io_data)
if (halt && epfile->isoc)
return -EINVAL;
/* We will be using request and read_buffer */
ret = ffs_mutex_lock(&epfile->mutex, file->f_flags & O_NONBLOCK);
if (unlikely(ret))
goto error;
/* Allocate & copy */
if (!halt) {
struct usb_gadget *gadget;
/*
* Do we have buffered data from previous partial read? Check
* that for synchronous case only because we do not have
* facility to ‘wake up’ a pending asynchronous read and push
* buffered data to it which we would need to make things behave
* consistently.
*/
if (!io_data->aio && io_data->read) {
ret = __ffs_epfile_read_buffered(epfile, &io_data->data);
if (ret)
goto error_mutex;
}
/*
* if we _do_ wait above, the epfile->ffs->gadget might be NULL
* before the waiting completes, so do not assign to 'gadget'
* earlier
*/
struct usb_gadget *gadget = epfile->ffs->gadget;
size_t copied;
gadget = epfile->ffs->gadget;
spin_lock_irq(&epfile->ffs->eps_lock);
/* In the meantime, endpoint got disabled or changed. */
if (epfile->ep != ep) {
spin_unlock_irq(&epfile->ffs->eps_lock);
return -ESHUTDOWN;
ret = -ESHUTDOWN;
goto error_lock;
}
data_len = iov_iter_count(&io_data->data);
/*
@ -771,22 +857,17 @@ static ssize_t ffs_epfile_io(struct file *file, struct ffs_io_data *io_data)
spin_unlock_irq(&epfile->ffs->eps_lock);
data = kmalloc(data_len, GFP_KERNEL);
if (unlikely(!data))
return -ENOMEM;
if (!io_data->read) {
copied = copy_from_iter(data, data_len, &io_data->data);
if (copied != data_len) {
ret = -EFAULT;
goto error;
}
if (unlikely(!data)) {
ret = -ENOMEM;
goto error_mutex;
}
if (!io_data->read &&
copy_from_iter(data, data_len, &io_data->data) != data_len) {
ret = -EFAULT;
goto error_mutex;
}
}
/* We will be using request */
ret = ffs_mutex_lock(&epfile->mutex, file->f_flags & O_NONBLOCK);
if (unlikely(ret))
goto error;
spin_lock_irq(&epfile->ffs->eps_lock);
if (epfile->ep != ep) {
@ -842,8 +923,8 @@ static ssize_t ffs_epfile_io(struct file *file, struct ffs_io_data *io_data)
if (interrupted)
ret = -EINTR;
else if (io_data->read && ep->status > 0)
ret = ffs_copy_to_iter(data, ep->status,
&io_data->data);
ret = __ffs_epfile_read_data(epfile, data, ep->status,
&io_data->data);
else
ret = ep->status;
goto error_mutex;
@ -1011,6 +1092,8 @@ ffs_epfile_release(struct inode *inode, struct file *file)
ENTER();
kfree(epfile->read_buffer);
epfile->read_buffer = NULL;
ffs_data_closed(epfile->ffs);
return 0;
@ -1636,19 +1719,24 @@ static void ffs_func_eps_disable(struct ffs_function *func)
unsigned count = func->ffs->eps_count;
unsigned long flags;
spin_lock_irqsave(&func->ffs->eps_lock, flags);
do {
if (epfile)
mutex_lock(&epfile->mutex);
spin_lock_irqsave(&func->ffs->eps_lock, flags);
/* pending requests get nuked */
if (likely(ep->ep))
usb_ep_disable(ep->ep);
++ep;
spin_unlock_irqrestore(&func->ffs->eps_lock, flags);
if (epfile) {
epfile->ep = NULL;
kfree(epfile->read_buffer);
epfile->read_buffer = NULL;
mutex_unlock(&epfile->mutex);
++epfile;
}
} while (--count);
spin_unlock_irqrestore(&func->ffs->eps_lock, flags);
}
static int ffs_func_eps_enable(struct ffs_function *func)