FAILED: patch "[PATCH] usb: xhci: Fix slot_id resource race conflict" failed to apply to 6.6-stable tree

[<gregkh@linuxfoundation.org>]

The patch below does not apply to the 6.6-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@vger.kernel.org>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.6.y
git checkout FETCH_HEAD
git cherry-pick -x 2eb03376151bb8585caa23ed2673583107bb5193
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable@vger.kernel.org>' --in-reply-to '2025082305-paddle-refute-2bd7@gregkh' --subject-prefix 'PATCH 6.6.y' HEAD^..

Possible dependencies:



thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 2eb03376151bb8585caa23ed2673583107bb5193 Mon Sep 17 00:00:00 2001
From: Weitao Wang <WeitaoWang-oc@zhaoxin.com>
Date: Tue, 19 Aug 2025 15:58:43 +0300
Subject: [PATCH] usb: xhci: Fix slot_id resource race conflict

xHC controller may immediately reuse a slot_id after it's disabled,
giving it to a new enumerating device before the xhci driver freed
all resources related to the disabled device.

In such a scenario, device-A with slot_id equal to 1 is disconnecting
while device-B is enumerating, device-B will fail to enumerate in the
follow sequence.

1.[device-A] send disable slot command
2.[device-B] send enable slot command
3.[device-A] disable slot command completed and wakeup waiting thread
4.[device-B] enable slot command completed with slot_id equal to 1 and
	     wakeup waiting thread
5.[device-B] driver checks that slot_id is still in use (by device-A) in
	     xhci_alloc_virt_device, and fail to enumerate due to this
	     conflict
6.[device-A] xhci->devs[slot_id] set to NULL in xhci_free_virt_device

To fix driver's slot_id resources conflict, clear xhci->devs[slot_id] and
xhci->dcbba->dev_context_ptrs[slot_id] pointers in the interrupt context
when disable slot command completes successfully. Simultaneously, adjust
function xhci_free_virt_device to accurately handle device release.

[minor smatch warning and commit message fix -Mathias]

Cc: stable@vger.kernel.org
Fixes: 7faac1953ed1 ("xhci: avoid race between disable slot command and host runtime suspend")
Signed-off-by: Weitao Wang <WeitaoWang-oc@zhaoxin.com>
Signed-off-by: Mathias Nyman <mathias.nyman@linux.intel.com>
Link: https://lore.kernel.org/r/20250819125844.2042452-2-mathias.nyman@linux.intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/usb/host/xhci-hub.c b/drivers/usb/host/xhci-hub.c
index 92bb84f8132a..b3a59ce1b3f4 100644
--- a/drivers/usb/host/xhci-hub.c
+++ b/drivers/usb/host/xhci-hub.c
@@ -704,8 +704,7 @@ static int xhci_enter_test_mode(struct xhci_hcd *xhci,
 		if (!xhci->devs[i])
 			continue;
 
-		retval = xhci_disable_slot(xhci, i);
-		xhci_free_virt_device(xhci, i);
+		retval = xhci_disable_and_free_slot(xhci, i);
 		if (retval)
 			xhci_err(xhci, "Failed to disable slot %d, %d. Enter test mode anyway\n",
 				 i, retval);
diff --git a/drivers/usb/host/xhci-mem.c b/drivers/usb/host/xhci-mem.c
index 07289333a1e8..81eaad87a3d9 100644
--- a/drivers/usb/host/xhci-mem.c
+++ b/drivers/usb/host/xhci-mem.c
@@ -865,21 +865,20 @@ int xhci_alloc_tt_info(struct xhci_hcd *xhci,
  * will be manipulated by the configure endpoint, allocate device, or update
  * hub functions while this function is removing the TT entries from the list.
  */
-void xhci_free_virt_device(struct xhci_hcd *xhci, int slot_id)
+void xhci_free_virt_device(struct xhci_hcd *xhci, struct xhci_virt_device *dev,
+		int slot_id)
 {
-	struct xhci_virt_device *dev;
 	int i;
 	int old_active_eps = 0;
 
 	/* Slot ID 0 is reserved */
-	if (slot_id == 0 || !xhci->devs[slot_id])
+	if (slot_id == 0 || !dev)
 		return;
 
-	dev = xhci->devs[slot_id];
-
-	xhci->dcbaa->dev_context_ptrs[slot_id] = 0;
-	if (!dev)
-		return;
+	/* If device ctx array still points to _this_ device, clear it */
+	if (dev->out_ctx &&
+	    xhci->dcbaa->dev_context_ptrs[slot_id] == cpu_to_le64(dev->out_ctx->dma))
+		xhci->dcbaa->dev_context_ptrs[slot_id] = 0;
 
 	trace_xhci_free_virt_device(dev);
 
@@ -920,8 +919,9 @@ void xhci_free_virt_device(struct xhci_hcd *xhci, int slot_id)
 		dev->udev->slot_id = 0;
 	if (dev->rhub_port && dev->rhub_port->slot_id == slot_id)
 		dev->rhub_port->slot_id = 0;
-	kfree(xhci->devs[slot_id]);
-	xhci->devs[slot_id] = NULL;
+	if (xhci->devs[slot_id] == dev)
+		xhci->devs[slot_id] = NULL;
+	kfree(dev);
 }
 
 /*
@@ -962,7 +962,7 @@ static void xhci_free_virt_devices_depth_first(struct xhci_hcd *xhci, int slot_i
 out:
 	/* we are now at a leaf device */
 	xhci_debugfs_remove_slot(xhci, slot_id);
-	xhci_free_virt_device(xhci, slot_id);
+	xhci_free_virt_device(xhci, vdev, slot_id);
 }
 
 int xhci_alloc_virt_device(struct xhci_hcd *xhci, int slot_id,
diff --git a/drivers/usb/host/xhci-ring.c b/drivers/usb/host/xhci-ring.c
index ecd757d482c5..4f8f5aab109d 100644
--- a/drivers/usb/host/xhci-ring.c
+++ b/drivers/usb/host/xhci-ring.c
@@ -1592,7 +1592,8 @@ static void xhci_handle_cmd_enable_slot(int slot_id, struct xhci_command *comman
 		command->slot_id = 0;
 }
 
-static void xhci_handle_cmd_disable_slot(struct xhci_hcd *xhci, int slot_id)
+static void xhci_handle_cmd_disable_slot(struct xhci_hcd *xhci, int slot_id,
+					u32 cmd_comp_code)
 {
 	struct xhci_virt_device *virt_dev;
 	struct xhci_slot_ctx *slot_ctx;
@@ -1607,6 +1608,10 @@ static void xhci_handle_cmd_disable_slot(struct xhci_hcd *xhci, int slot_id)
 	if (xhci->quirks & XHCI_EP_LIMIT_QUIRK)
 		/* Delete default control endpoint resources */
 		xhci_free_device_endpoint_resources(xhci, virt_dev, true);
+	if (cmd_comp_code == COMP_SUCCESS) {
+		xhci->dcbaa->dev_context_ptrs[slot_id] = 0;
+		xhci->devs[slot_id] = NULL;
+	}
 }
 
 static void xhci_handle_cmd_config_ep(struct xhci_hcd *xhci, int slot_id)
@@ -1856,7 +1861,7 @@ static void handle_cmd_completion(struct xhci_hcd *xhci,
 		xhci_handle_cmd_enable_slot(slot_id, cmd, cmd_comp_code);
 		break;
 	case TRB_DISABLE_SLOT:
-		xhci_handle_cmd_disable_slot(xhci, slot_id);
+		xhci_handle_cmd_disable_slot(xhci, slot_id, cmd_comp_code);
 		break;
 	case TRB_CONFIG_EP:
 		if (!cmd->completion)
diff --git a/drivers/usb/host/xhci.c b/drivers/usb/host/xhci.c
index 47151ca527bf..0e03691f03bf 100644
--- a/drivers/usb/host/xhci.c
+++ b/drivers/usb/host/xhci.c
@@ -3932,8 +3932,7 @@ static int xhci_discover_or_reset_device(struct usb_hcd *hcd,
 		 * Obtaining a new device slot to inform the xHCI host that
 		 * the USB device has been reset.
 		 */
-		ret = xhci_disable_slot(xhci, udev->slot_id);
-		xhci_free_virt_device(xhci, udev->slot_id);
+		ret = xhci_disable_and_free_slot(xhci, udev->slot_id);
 		if (!ret) {
 			ret = xhci_alloc_dev(hcd, udev);
 			if (ret == 1)
@@ -4090,7 +4089,7 @@ static void xhci_free_dev(struct usb_hcd *hcd, struct usb_device *udev)
 	xhci_disable_slot(xhci, udev->slot_id);
 
 	spin_lock_irqsave(&xhci->lock, flags);
-	xhci_free_virt_device(xhci, udev->slot_id);
+	xhci_free_virt_device(xhci, virt_dev, udev->slot_id);
 	spin_unlock_irqrestore(&xhci->lock, flags);
 
 }
@@ -4139,6 +4138,16 @@ int xhci_disable_slot(struct xhci_hcd *xhci, u32 slot_id)
 	return 0;
 }
 
+int xhci_disable_and_free_slot(struct xhci_hcd *xhci, u32 slot_id)
+{
+	struct xhci_virt_device *vdev = xhci->devs[slot_id];
+	int ret;
+
+	ret = xhci_disable_slot(xhci, slot_id);
+	xhci_free_virt_device(xhci, vdev, slot_id);
+	return ret;
+}
+
 /*
  * Checks if we have enough host controller resources for the default control
  * endpoint.
@@ -4245,8 +4254,7 @@ int xhci_alloc_dev(struct usb_hcd *hcd, struct usb_device *udev)
 	return 1;
 
 disable_slot:
-	xhci_disable_slot(xhci, udev->slot_id);
-	xhci_free_virt_device(xhci, udev->slot_id);
+	xhci_disable_and_free_slot(xhci, udev->slot_id);
 
 	return 0;
 }
@@ -4382,8 +4390,7 @@ static int xhci_setup_device(struct usb_hcd *hcd, struct usb_device *udev,
 		dev_warn(&udev->dev, "Device not responding to setup %s.\n", act);
 
 		mutex_unlock(&xhci->mutex);
-		ret = xhci_disable_slot(xhci, udev->slot_id);
-		xhci_free_virt_device(xhci, udev->slot_id);
+		ret = xhci_disable_and_free_slot(xhci, udev->slot_id);
 		if (!ret) {
 			if (xhci_alloc_dev(hcd, udev) == 1)
 				xhci_setup_addressable_virt_dev(xhci, udev);
diff --git a/drivers/usb/host/xhci.h b/drivers/usb/host/xhci.h
index a20f4e7cd43a..85d5b964bf1e 100644
--- a/drivers/usb/host/xhci.h
+++ b/drivers/usb/host/xhci.h
@@ -1791,7 +1791,7 @@ void xhci_dbg_trace(struct xhci_hcd *xhci, void (*trace)(struct va_format *),
 /* xHCI memory management */
 void xhci_mem_cleanup(struct xhci_hcd *xhci);
 int xhci_mem_init(struct xhci_hcd *xhci, gfp_t flags);
-void xhci_free_virt_device(struct xhci_hcd *xhci, int slot_id);
+void xhci_free_virt_device(struct xhci_hcd *xhci, struct xhci_virt_device *dev, int slot_id);
 int xhci_alloc_virt_device(struct xhci_hcd *xhci, int slot_id, struct usb_device *udev, gfp_t flags);
 int xhci_setup_addressable_virt_dev(struct xhci_hcd *xhci, struct usb_device *udev);
 void xhci_copy_ep0_dequeue_into_input_ctx(struct xhci_hcd *xhci,
@@ -1888,6 +1888,7 @@ void xhci_reset_bandwidth(struct usb_hcd *hcd, struct usb_device *udev);
 int xhci_update_hub_device(struct usb_hcd *hcd, struct usb_device *hdev,
 			   struct usb_tt *tt, gfp_t mem_flags);
 int xhci_disable_slot(struct xhci_hcd *xhci, u32 slot_id);
+int xhci_disable_and_free_slot(struct xhci_hcd *xhci, u32 slot_id);
 int xhci_ext_cap_init(struct xhci_hcd *xhci);
 
 int xhci_suspend(struct xhci_hcd *xhci, bool do_wakeup);