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@xxxxxxxxxx> --- drivers/usb/gadget/function/f_fs.c | 130 +++++++++++++++++++++++++++++++------ 1 file changed, 109 insertions(+), 21 deletions(-) diff --git a/drivers/usb/gadget/function/f_fs.c b/drivers/usb/gadget/function/f_fs.c index e26a6b4..08a1ac2 100644 --- a/drivers/usb/gadget/function/f_fs.c +++ b/drivers/usb/gadget/function/f_fs.c @@ -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. @@ -717,6 +734,56 @@ 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; @@ -746,21 +813,40 @@ 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); /* @@ -772,22 +858,17 @@ 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) { @@ -843,8 +924,8 @@ 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; @@ -1012,6 +1093,8 @@ 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; @@ -1637,19 +1720,24 @@ 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) -- 2.8.0.rc3.226.g39d4020 -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html