[PATCH 5.12 104/296] usb: gadget: udc: renesas_usb3: Fix a race in usb3_start_pipen()

Greg Kroah-Hartman
2021-05-31T16:23:18Z

From: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>

commit e752dbc59e1241b13b8c4f7b6eb582862e7668fe upstream.

The usb3_start_pipen() is called by renesas_usb3_ep_queue() and
usb3_request_done_pipen() so that usb3_start_pipen() is possible
to cause a race when getting usb3_first_req like below:

renesas_usb3_ep_queue()
spin_lock_irqsave()
list_add_tail()
spin_unlock_irqrestore()
usb3_start_pipen()
usb3_first_req = usb3_get_request() --- [1]
--- interrupt ---
usb3_irq_dma_int()
usb3_request_done_pipen()
usb3_get_request()
usb3_start_pipen()
usb3_first_req = usb3_get_request()
...
(the req is possible to be finished in the interrupt)

The usb3_first_req [1] above may have been finished after the interrupt
ended so that this driver caused to start a transfer wrongly. To fix this
issue, getting/checking the usb3_first_req are under spin_lock_irqsave()
in the same section.

Fixes: 746bfe63bba3 ("usb: gadget: renesas_usb3: add support for Renesas USB3.0 peripheral controller")
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
Link: https://lore.kernel.org/r/20210524060155.1178724-1-yoshihiro.shimoda.uh@renesas.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/usb/gadget/udc/renesas_usb3.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)

--- a/drivers/usb/gadget/udc/renesas_usb3.c
+++ b/drivers/usb/gadget/udc/renesas_usb3.c
@@ -1488,7 +1488,7 @@ static void usb3_start_pipen(struct rene
struct renesas_usb3_request *usb3_req)
{
struct renesas_usb3 *usb3 = usb3_ep_to_usb3(usb3_ep);
- struct renesas_usb3_request *usb3_req_first = usb3_get_request(usb3_ep);
+ struct renesas_usb3_request *usb3_req_first;
unsigned long flags;
int ret = -EAGAIN;
u32 enable_bits = 0;
@@ -1496,7 +1496,8 @@ static void usb3_start_pipen(struct rene
spin_lock_irqsave(&usb3->lock, flags);
if (usb3_ep->halt || usb3_ep->started)
goto out;
- if (usb3_req != usb3_req_first)
+ usb3_req_first = __usb3_get_request(usb3_ep);
+ if (!usb3_req_first || usb3_req != usb3_req_first)
goto out;

if (usb3_pn_change(usb3, usb3_ep->num) < 0)