usbip: Fix locking bug in RT-enabled kernels

Interrupts are disabled before entering usb_hcd_giveback_urb().
A spinlock_t becomes a sleeping lock on PREEMPT_RT, so it cannot be
acquired with disabled interrupts.

Save the interrupt status and restore it after usb_hcd_giveback_urb().

syz reported:
BUG: sleeping function called from invalid context at kernel/locking/spinlock_rt.c:48
Call Trace:
 dump_stack_lvl+0x189/0x250 lib/dump_stack.c:120
 rt_spin_lock+0xc7/0x2c0 kernel/locking/spinlock_rt.c:57
 spin_lock include/linux/spinlock_rt.h:44 [inline]
 mon_bus_complete drivers/usb/mon/mon_main.c:134 [inline]
 mon_complete+0x5c/0x200 drivers/usb/mon/mon_main.c:147
 usbmon_urb_complete include/linux/usb/hcd.h:738 [inline]
 __usb_hcd_giveback_urb+0x254/0x5e0 drivers/usb/core/hcd.c:1647
 vhci_urb_enqueue+0xb4f/0xe70 drivers/usb/usbip/vhci_hcd.c:818

Reported-by: syzbot+205ef33a3b636b4181fb@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=205ef33a3b636b4181fb
Signed-off-by: Lizhi Xu <lizhi.xu@windriver.com>
Acked-by: Shuah Khan <skhan@linuxfoundation.org>
Link: https://lore.kernel.org/r/20250916014143.1439759-1-lizhi.xu@windriver.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/usb/usbip/vhci_hcd.c b/drivers/usb/usbip/vhci_hcd.c
index 0d6c10a8490c0b3fdbebbc98c856a6c0c9b477cf..f7e405abe6084988484c35d99a7d99220c4e0735 100644 (file)
--- a/drivers/usb/usbip/vhci_hcd.c
+++ b/drivers/usb/usbip/vhci_hcd.c
@@ -831,15 +831,15 @@ out:
 no_need_xmit:
        usb_hcd_unlink_urb_from_ep(hcd, urb);
 no_need_unlink:
-       spin_unlock_irqrestore(&vhci->lock, flags);
        if (!ret) {
                /* usb_hcd_giveback_urb() should be called with
                 * irqs disabled
                 */
-               local_irq_disable();
+               spin_unlock(&vhci->lock);
                usb_hcd_giveback_urb(hcd, urb, urb->status);
-               local_irq_enable();
+               spin_lock(&vhci->lock);
        }
+       spin_unlock_irqrestore(&vhci->lock, flags);
        return ret;
 }