[PATCHv2 2/2] check quirk to pad epout buf size when not aligned to maxpacketsize

[Michal Nazarewicz <mina86@mina86.com>]

Check gadget.quirk_ep_out_aligned_size to decide if buffer size requires
to be aligned to maxpacketsize of an out endpoint.  ffs_epfile_io() needs
to pad epout buffer to match above condition if quirk is found.

Signed-off-by: Michal Nazarewicz <mina86@mina86.com>
---
 drivers/usb/gadget/f_fs.c | 23 +++++++++++++++++++----
 1 file changed, 19 insertions(+), 4 deletions(-)

> On 11/10/2013 08:50 AM, Michal Nazarewicz wrote:
>> @@ -787,6 +788,13 @@ static ssize_t ffs_epfile_io(struct file *file,
>>  
>>  	/* Allocate & copy */
>>  	if (!halt) {
>> +		/*
>> +		 * Controller requires buffer size to be aligned to
>> +		 * maxpacketsize of an out endpoint.
>> +		 */
>> +		data_len = read && gadget->quirk_ep_out_aligned_size ?
>> +			usb_ep_align_maxpacketsize(ep->ep, len) : len;
>> +
>>  		data = kmalloc(len, GFP_KERNEL);

On Mon, Nov 11 2013, David Cohen <david.a.cohen@linux.intel.com> wrote:
> Shouldn't this kmalloc() allocate 'data_len' bytes, instead of 'len'?

Yes, of coures.

diff --git a/drivers/usb/gadget/f_fs.c b/drivers/usb/gadget/f_fs.c
index e496b72..fd769a8 100644
--- a/drivers/usb/gadget/f_fs.c
+++ b/drivers/usb/gadget/f_fs.c
@@ -753,8 +753,9 @@ static ssize_t ffs_epfile_io(struct file *file,
 			     char __user *buf, size_t len, int read)
 {
 	struct ffs_epfile *epfile = file->private_data;
+	struct usb_gadget *gadget = epfile->ffs->gadget;
 	struct ffs_ep *ep;
-	ssize_t ret;
+	ssize_t ret, data_len;
 	char *data;
 	int halt;
 
@@ -787,7 +788,14 @@ static ssize_t ffs_epfile_io(struct file *file,
 
 	/* Allocate & copy */
 	if (!halt) {
-		data = kmalloc(len, GFP_KERNEL);
+		/*
+		 * Controller requires buffer size to be aligned to
+		 * maxpacketsize of an out endpoint.
+		 */
+		data_len = read && gadget->quirk_ep_out_aligned_size ?
+			usb_ep_align_maxpacketsize(ep->ep, len) : len;
+
+		data = kmalloc(data_len, GFP_KERNEL);
 		if (unlikely(!data))
 			return -ENOMEM;
 
@@ -824,7 +832,7 @@ static ssize_t ffs_epfile_io(struct file *file,
 		req->context  = &done;
 		req->complete = ffs_epfile_io_complete;
 		req->buf      = data;
-		req->length   = len;
+		req->length   = data_len;
 
 		ret = usb_ep_queue(ep->ep, req, GFP_ATOMIC);
 
@@ -836,9 +844,16 @@ static ssize_t ffs_epfile_io(struct file *file,
 			ret = -EINTR;
 			usb_ep_dequeue(ep->ep, req);
 		} else {
+			/*
+			 * XXX We may end up silently droping data here.
+			 * Since data_len (i.e. req->length) may be bigger
+			 * than len (after being rounded up to maxpacketsize),
+			 * we may end up with more data then user space has
+			 * space for.
+			 */
 			ret = ep->status;
 			if (read && ret > 0 &&
-			    unlikely(copy_to_user(buf, data, ret)))
+			    unlikely(copy_to_user(buf, data, min(ret, len))))
 				ret = -EFAULT;
 		}
 	}
-- 
1.8.4.1