4.2.8-ckt12 -stable review patch. If anyone has any objections, please let me know.
---8<------------------------------------------------------------ From: Lars-Peter Clausen <[email protected]> commit 332a5b446b7916d272c2a659a3b20909ce34d2c1 upstream. In the current implementation functionfs generates a EFAULT for async read operations if the read buffer size is larger than the URB data size. Since a application does not necessarily know how much data the host side is going to send it typically supplies a buffer larger than the actual data, which will then result in a EFAULT error. This behaviour was introduced while refactoring the code to use iov_iter interface in commit c993c39b8639 ("gadget/function/f_fs.c: use put iov_iter into io_data"). The original code took the minimum over the URB size and the user buffer size and then attempted to copy that many bytes using copy_to_user(). If copy_to_user() could not copy all data a EFAULT error was generated. Restore the original behaviour by only generating a EFAULT error when the number of bytes copied is not the size of the URB and the target buffer has not been fully filled. Commit 342f39a6c8d3 ("usb: gadget: f_fs: fix check in read operation") already fixed the same problem for the synchronous read path. Fixes: c993c39b8639 ("gadget/function/f_fs.c: use put iov_iter into io_data") Acked-by: Michal Nazarewicz <[email protected]> Signed-off-by: Lars-Peter Clausen <[email protected]> Signed-off-by: Felipe Balbi <[email protected]> Signed-off-by: Kamal Mostafa <[email protected]> --- drivers/usb/gadget/function/f_fs.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/usb/gadget/function/f_fs.c b/drivers/usb/gadget/function/f_fs.c index 82240db..db9433e 100644 --- a/drivers/usb/gadget/function/f_fs.c +++ b/drivers/usb/gadget/function/f_fs.c @@ -651,7 +651,7 @@ static void ffs_user_copy_worker(struct work_struct *work) if (io_data->read && ret > 0) { use_mm(io_data->mm); ret = copy_to_iter(io_data->buf, ret, &io_data->data); - if (iov_iter_count(&io_data->data)) + if (ret != io_data->req->actual && iov_iter_count(&io_data->data)) ret = -EFAULT; unuse_mm(io_data->mm); } -- 2.7.4
