linux-kernel - [PATCH 4.9 66/70] xhci: Fix use-after-free in xhci_free_virt

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Message-Id: <20180917211654.286753406@linuxfoundation.org>
Date:   Tue, 18 Sep 2018 00:42:39 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Guenter Roeck <linux@...ck-us.net>,
        Mathias Nyman <mathias.nyman@...ux.intel.com>,
        Matthias Kaehlcke <mka@...omium.org>
Subject: [PATCH 4.9 66/70] xhci: Fix use-after-free in xhci_free_virt_device

4.9-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Mathias Nyman <mathias.nyman@...ux.intel.com>

commit 44a182b9d17765514fa2b1cc911e4e65134eef93 upstream.

KASAN found a use-after-free in xhci_free_virt_device+0x33b/0x38e
where xhci_free_virt_device() sets slot id to 0 if udev exists:
if (dev->udev && dev->udev->slot_id)
	dev->udev->slot_id = 0;

dev->udev will be true even if udev is freed because dev->udev is
not set to NULL.

set dev->udev pointer to NULL in xhci_free_dev()

The original patch went to stable so this fix needs to be applied
there as well.

Fixes: a400efe455f7 ("xhci: zero usb device slot_id member when disabling and freeing a xhci slot")
Cc: <stable@...r.kernel.org>
Reported-by: Guenter Roeck <linux@...ck-us.net>
Reviewed-by: Guenter Roeck <linux@...ck-us.net>
Tested-by: Guenter Roeck <linux@...ck-us.net>
Signed-off-by: Mathias Nyman <mathias.nyman@...ux.intel.com>
Signed-off-by: Matthias Kaehlcke <mka@...omium.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 drivers/usb/host/xhci.c |    3 +++
 1 file changed, 3 insertions(+)

--- a/drivers/usb/host/xhci.c
+++ b/drivers/usb/host/xhci.c
@@ -3656,6 +3656,9 @@ void xhci_free_dev(struct usb_hcd *hcd,
 	}
 
 	spin_lock_irqsave(&xhci->lock, flags);
+
+	virt_dev->udev = NULL;
+
 	/* Don't disable the slot if the host controller is dead. */
 	state = readl(&xhci->op_regs->status);
 	if (state == 0xffffffff || (xhci->xhc_state & XHCI_STATE_DYING) ||