queue-6.6/usbip-fix-locking-bug-in-rt-enabled-kernels.patch

From eb9c1d5d70093ac4467fd85e507101a8fb01e234 Mon Sep 17 00:00:00 2001
From: Sasha Levin <sashal@kernel.org>
Date: Tue, 16 Sep 2025 09:41:43 +0800
Subject: usbip: Fix locking bug in RT-enabled kernels

From: Lizhi Xu <lizhi.xu@windriver.com>

[ Upstream commit 09bf21bf5249880f62fe759b53b14b4b52900c6c ]

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>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/usb/usbip/vhci_hcd.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/usb/usbip/vhci_hcd.c b/drivers/usb/usbip/vhci_hcd.c
index b22e0881bfaf..0bc4805cfa3e 100644
--- a/drivers/usb/usbip/vhci_hcd.c
+++ b/drivers/usb/usbip/vhci_hcd.c
@@ -830,15 +830,15 @@ static int vhci_urb_enqueue(struct usb_hcd *hcd, struct urb *urb, gfp_t mem_flag
 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;
 }
 
-- 
2.51.0