linux-kernel - [PATCH 4.13 24/85] xhci: Cleanup current_cmd in xhci_cleanup_command

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Date:   Tue, 24 Oct 2017 15:06:58 +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, Jeffy Chen <jeffy.chen@...k-chips.com>,
        Mathias Nyman <mathias.nyman@...ux.intel.com>
Subject: [PATCH 4.13 24/85] xhci: Cleanup current_cmd in xhci_cleanup_command_queue()

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

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

From: Jeffy Chen <jeffy.chen@...k-chips.com>

commit d1aad52cf8b3f95dfe9b5b64da66343306ddf73b upstream.

KASAN reported use-after-free bug when xhci host controller died:
[  176.952537] BUG: KASAN: use-after-free in xhci_handle_command_timeout+0x68/0x224
[  176.960846] Write of size 4 at addr ffffffc0cbb01608 by task kworker/3:3/1680
...
[  177.180644] Freed by task 0:
[  177.183882]  kasan_slab_free+0x90/0x15c
[  177.188194]  kfree+0x114/0x28c
[  177.191630]  xhci_cleanup_command_queue+0xc8/0xf8
[  177.196916]  xhci_hc_died+0x84/0x358

Problem here is that when the cmd_timer fired, it would try to access
current_cmd while the command queue is already freed by xhci_hc_died().

Cleanup current_cmd in xhci_cleanup_command_queue() to avoid that.

Fixes: d9f11ba9f107 ("xhci: Rework how we handle unresponsive or hoptlug removed hosts")
Signed-off-by: Jeffy Chen <jeffy.chen@...k-chips.com>
Signed-off-by: Mathias Nyman <mathias.nyman@...ux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

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

--- a/drivers/usb/host/xhci-ring.c
+++ b/drivers/usb/host/xhci-ring.c
@@ -1309,6 +1309,7 @@ static void xhci_complete_del_and_free_c
 void xhci_cleanup_command_queue(struct xhci_hcd *xhci)
 {
 	struct xhci_command *cur_cmd, *tmp_cmd;
+	xhci->current_cmd = NULL;
 	list_for_each_entry_safe(cur_cmd, tmp_cmd, &xhci->cmd_list, cmd_list)
 		xhci_complete_del_and_free_cmd(cur_cmd, COMP_COMMAND_ABORTED);
 }