usb: subtle increased memory usage in u_serial

OK, the USB gadget serial driver actually has a couple of problems.  On
gs_open(), it always allocates and queues an additional QUEUE_SIZE (16)
worth of requests, so with a loop like this:

    i=1 ; while echo $i > /dev/ttyGS0 ; do let i++ ; done

eventually we run into OOM (Out of Memory).

Technically, it is not a leak as everything gets freed up when the USB
connection is broken, but not on gs_close().

With a USB device/gadget controller driver that has limited resources
(e.g., Marvell has a this MAX_XDS_FOR_TR_CALLS of 64 for transmit and
receive), so even after 4

    stty -F /dev/ttyGS0

we cannot transmit anymore.  We can still receive (not necessarily
reliably) as now we have 16 * 4 = 64 descriptors/buffers ready, but the
device is otherwise not usable.

Signed-off-by: Jim Sung <jsung@syncadence.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

1 files changed, 40 insertions, 14 deletions

diff --git a/drivers/usb/gadget/u_serial.c b/drivers/usb/gadget/u_serial.c
index 01e5354a4c20..40f7716b31fc 100644
--- a/drivers/usb/gadget/u_serial.c
+++ b/drivers/usb/gadget/u_serial.c
@@ -105,11 +105,15 @@ struct gs_port {
         wait_queue_head_t       close_wait;     /* wait for last close */
 
         struct list_head        read_pool;
+        int read_started;
+        int read_allocated;
         struct list_head        read_queue;
         unsigned                n_read;
         struct tasklet_struct   push;
 
         struct list_head        write_pool;
+        int write_started;
+        int write_allocated;
         struct gs_buf           port_write_buf;
         wait_queue_head_t       drain_wait;     /* wait while writes drain */
 
@@ -363,6 +367,9 @@ __acquires(&port->port_lock)
                 struct usb_request      *req;
                 int                     len;
 
+                if (port->write_started >= QUEUE_SIZE)
+                        break;
+
                 req = list_entry(pool->next, struct usb_request, list);
                 len = gs_send_packet(port, req->buf, in->maxpacket);
                 if (len == 0) {
@@ -397,6 +404,8 @@ __acquires(&port->port_lock)
                         break;
                 }
 
+                port->write_started++;
+
                 /* abort immediately after disconnect */
                 if (!port->port_usb)
                         break;
@@ -418,7 +427,6 @@ __acquires(&port->port_lock)
 {
         struct list_head        *pool = &port->read_pool;
         struct usb_ep           *out = port->port_usb->out;
-        unsigned                started = 0;
 
         while (!list_empty(pool)) {
                 struct usb_request      *req;
@@ -430,6 +438,9 @@ __acquires(&port->port_lock)
                 if (!tty)
                         break;
 
+                if (port->read_started >= QUEUE_SIZE)
+                        break;
+
                 req = list_entry(pool->next, struct usb_request, list);
                 list_del(&req->list);
                 req->length = out->maxpacket;
@@ -447,13 +458,13 @@ __acquires(&port->port_lock)
                         list_add(&req->list, pool);
                         break;
                 }
-                started++;
+                port->read_started++;
 
                 /* abort immediately after disconnect */
                 if (!port->port_usb)
                         break;
         }
-        return started;
+        return port->read_started;
 }
 
 /*
@@ -535,6 +546,7 @@ static void gs_rx_push(unsigned long _port)
                 }
 recycle:
                 list_move(&req->list, &port->read_pool);
+                port->read_started--;
         }
 
         /* Push from tty to ldisc; without low_latency set this is handled by
@@ -587,6 +599,7 @@ static void gs_write_complete(struct usb_ep *ep, struct usb_request *req)
 
         spin_lock(&port->port_lock);
         list_add(&req->list, &port->write_pool);
+        port->write_started--;
 
         switch (req->status) {
         default:
@@ -608,7 +621,8 @@ static void gs_write_complete(struct usb_ep *ep, struct usb_request *req)
         spin_unlock(&port->port_lock);
 }
 
-static void gs_free_requests(struct usb_ep *ep, struct list_head *head)
+static void gs_free_requests(struct usb_ep *ep, struct list_head *head,
+                                                         int *allocated)
 {
         struct usb_request      *req;
 
@@ -616,25 +630,31 @@ static void gs_free_requests(struct usb_ep *ep, struct list_head *head)
                 req = list_entry(head->next, struct usb_request, list);
                 list_del(&req->list);
                 gs_free_req(ep, req);
+                if (allocated)
+                        (*allocated)--;
         }
 }
 
 static int gs_alloc_requests(struct usb_ep *ep, struct list_head *head,
-                void (*fn)(struct usb_ep *, struct usb_request *))
+                void (*fn)(struct usb_ep *, struct usb_request *),
+                int *allocated)
 {
         int                     i;
         struct usb_request      *req;
+        int n = allocated ? QUEUE_SIZE - *allocated : QUEUE_SIZE;
 
         /* Pre-allocate up to QUEUE_SIZE transfers, but if we can't
          * do quite that many this time, don't fail ... we just won't
          * be as speedy as we might otherwise be.
          */
-        for (i = 0; i < QUEUE_SIZE; i++) {
+        for (i = 0; i < n; i++) {
                 req = gs_alloc_req(ep, ep->maxpacket, GFP_ATOMIC);
                 if (!req)
                         return list_empty(head) ? -ENOMEM : 0;
                 req->complete = fn;
                 list_add_tail(&req->list, head);
+                if (allocated)
+                        (*allocated)++;
         }
         return 0;
 }
@@ -661,14 +681,15 @@ static int gs_start_io(struct gs_port *port)
          * configurations may use different endpoints with a given port;
          * and high speed vs full speed changes packet sizes too.
          */
-        status = gs_alloc_requests(ep, head, gs_read_complete);
+        status = gs_alloc_requests(ep, head, gs_read_complete,
+                &port->read_allocated);
         if (status)
                 return status;
 
         status = gs_alloc_requests(port->port_usb->in, &port->write_pool,
-                        gs_write_complete);
+                        gs_write_complete, &port->write_allocated);
         if (status) {
-                gs_free_requests(ep, head);
+                gs_free_requests(ep, head, &port->read_allocated);
                 return status;
         }
 
@@ -680,8 +701,9 @@ static int gs_start_io(struct gs_port *port)
         if (started) {
                 tty_wakeup(port->port_tty);
         } else {
-                gs_free_requests(ep, head);
-                gs_free_requests(port->port_usb->in, &port->write_pool);
+                gs_free_requests(ep, head, &port->read_allocated);
+                gs_free_requests(port->port_usb->in, &port->write_pool,
+                        &port->write_allocated);
                 status = -EIO;
         }
 
@@ -1315,8 +1337,12 @@ void gserial_disconnect(struct gserial *gser)
         spin_lock_irqsave(&port->port_lock, flags);
         if (port->open_count == 0 && !port->openclose)
                 gs_buf_free(&port->port_write_buf);
-        gs_free_requests(gser->out, &port->read_pool);
-        gs_free_requests(gser->out, &port->read_queue);
-        gs_free_requests(gser->in, &port->write_pool);
+        gs_free_requests(gser->out, &port->read_pool, NULL);
+        gs_free_requests(gser->out, &port->read_queue, NULL);
+        gs_free_requests(gser->in, &port->write_pool, NULL);
+
+        port->read_allocated = port->read_started =
+                port->write_allocated = port->write_started = 0;
+
         spin_unlock_irqrestore(&port->port_lock, flags);
 }