usb: gadget: ffs: race between ffs_epfile_io() and ffs_func_eps_disable()
ffs_epfile_io() is called from userspace, while ffs_func_eps_disable() might be
called from USB disconnect interrupt, the two functions would run in parallel
but they are not well protected, that epfile->ep would be removed by
ffs_func_eps_disable() during ffs_epfile_io() is referring this pointer, then
it leads to kernel PANIC.
The scenario is as below:
Thread 1 Thread 2
| |
SyS_read dwc3_gadget_disconnect_interrupt
| |
ffs_epfile_read reset_config
| |
ffs_epfile_io ffs_func_eps_disable
| |
----- usb_ep_disable(): epfile->ep->ep->desc = NULL
| |
usb_ep_align_maybe(): -----
it refers ep->desc->wMaxPacketSize -----
Signed-off-by: Chao Bi <chao.bi@intel.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>
diff --git a/drivers/usb/gadget/f_fs.c b/drivers/usb/gadget/f_fs.c
index 2e164dc..1e12b3e 100644
--- a/drivers/usb/gadget/f_fs.c
+++ b/drivers/usb/gadget/f_fs.c
@@ -745,6 +745,12 @@
*/
struct usb_gadget *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;
+ }
/*
* Controller may require buffer size to be aligned to
* maxpacketsize of an out endpoint.
@@ -752,6 +758,7 @@
data_len = io_data->read ?
usb_ep_align_maybe(gadget, ep->ep, io_data->len) :
io_data->len;
+ spin_unlock_irq(&epfile->ffs->eps_lock);
data = kmalloc(data_len, GFP_KERNEL);
if (unlikely(!data))