[PATCH] USB: gadget: fix NULL pointer dereference in gadget_dev_ioctl()

[Lovekesh Solanki <lovekeshsolanki00@gmail.com>]

gadget_dev_ioctl() reads dev->gadget outside the dev->lock, while
gadgetfs_bind() writes it without holding the lock. A concurrent
bind can update dev->gadget and dev->state under the lock while the
ioctl thread holds a stale NULL copy, causing a NULL pointer
dereference at offset 0x28 (gadget->ops->ioctl).

Read dev->gadget inside the locked region, before the state check,
so the state and gadget pointer are always consistent.

Cc: stable@vger.kernel.org
Reported-by: Eulgyu Kim <eulgyukim@snu.ac.kr>
Link: https://lore.kernel.org/all/20260824160022.2378192-1-jjy600901@snu.ac.kr/
Reported-by: Jaeyoung Chung <jjy600901@snu.ac.kr>
Link: https://lore.kernel.org/all/20260824160022.2378192-1-jjy600901@snu.ac.kr/
Signed-off-by: Lovekesh Solanki <lovekeshsolanki00@gmail.com>
---
 drivers/usb/gadget/legacy/inode.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/usb/gadget/legacy/inode.c b/drivers/usb/gadget/legacy/inode.c
index d87a8ab51510..e9f7d7c1a6a3 100644
--- a/drivers/usb/gadget/legacy/inode.c
+++ b/drivers/usb/gadget/legacy/inode.c
@@ -1251,14 +1251,15 @@ ep0_poll (struct file *fd, poll_table *wait)
 static long gadget_dev_ioctl (struct file *fd, unsigned code, unsigned long value)
 {
 	struct dev_data		*dev = fd->private_data;
-	struct usb_gadget	*gadget = dev->gadget;
+	struct usb_gadget	*gadget;
 	long ret = -ENOTTY;
 
 	spin_lock_irq(&dev->lock);
+	gadget = dev->gadget;
 	if (dev->state == STATE_DEV_OPENED ||
 			dev->state == STATE_DEV_UNBOUND) {
 		/* Not bound to a UDC */
-	} else if (gadget->ops->ioctl) {
+	} else if (gadget && gadget->ops->ioctl) {
 		++dev->udc_usage;
 		spin_unlock_irq(&dev->lock);
 
-- 
2.55.0