linux-kernel - [PATCH] usb: xhci: Fix xhci_free_virt_devices_depth

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Message-ID: <20250902093017.13d6c666.michal.pecio@gmail.com>
Date: Tue, 2 Sep 2025 09:30:17 +0200
From: Michal Pecio <michal.pecio@...il.com>
To: Mathias Nyman <mathias.nyman@...ux.intel.com>
Cc: David Wang <00107082@....com>, WeitaoWang-oc@...oxin.com,
 gregkh@...uxfoundation.org, linux-usb@...r.kernel.org,
 regressions@...ts.linux.dev, linux-kernel@...r.kernel.org,
 surenb@...gle.com, kent.overstreet@...ux.dev
Subject: [PATCH] usb: xhci: Fix xhci_free_virt_devices_depth_first()

Reusing 'vdev' for iteration caused a recent commit to malfunction
uexpectedly, resulting in a reported memory leak and potential UAF
if devices are freed in bad order. Using a second variable solves
this problem, and maybe others later.

HCS_MAX_SLOTS(xhci->hcs_params1) is the highest possible slot_id,
so change the iteration range to include it. Currently this doesn't
seem to cause problems because the only caller begins with freeing
the topmost slot_id, but it breaks documented functionality.

Reported-by: David Wang <00107082@....com>
Closes: https://lore.kernel.org/linux-usb/20250829181354.4450-1-00107082@163.com/
Fixes: 2eb03376151b ("usb: xhci: Fix slot_id resource race conflict")
Fixes: ee8665e28e8d ("xhci: free xhci virtual devices with leaf nodes first")
Cc: stable@...r.kernel.org
Signed-off-by: Michal Pecio <michal.pecio@...il.com>
---
 drivers/usb/host/xhci-mem.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/drivers/usb/host/xhci-mem.c b/drivers/usb/host/xhci-mem.c
index eed5926b200e..db7dc70c37e5 100644
--- a/drivers/usb/host/xhci-mem.c
+++ b/drivers/usb/host/xhci-mem.c
@@ -932,7 +932,7 @@ void xhci_free_virt_device(struct xhci_hcd *xhci, struct xhci_virt_device *dev,
  */
 static void xhci_free_virt_devices_depth_first(struct xhci_hcd *xhci, int slot_id)
 {
-	struct xhci_virt_device *vdev;
+	struct xhci_virt_device *vdev, *vdev_i;
 	struct list_head *tt_list_head;
 	struct xhci_tt_bw_info *tt_info, *next;
 	int i;
@@ -951,9 +951,9 @@ static void xhci_free_virt_devices_depth_first(struct xhci_hcd *xhci, int slot_i
 		/* is this a hub device that added a tt_info to the tts list */
 		if (tt_info->slot_id == slot_id) {
 			/* are any devices using this tt_info? */
-			for (i = 1; i < HCS_MAX_SLOTS(xhci->hcs_params1); i++) {
-				vdev = xhci->devs[i];
-				if (vdev && (vdev->tt_info == tt_info))
+			for (i = 1; i <= HCS_MAX_SLOTS(xhci->hcs_params1); i++) {
+				vdev_i = xhci->devs[i];
+				if (vdev_i && (vdev_i->tt_info == tt_info))
 					xhci_free_virt_devices_depth_first(
 						xhci, i);
 			}
-- 
2.48.1