patch "xhci: Cleanup current_cmd in xhci_cleanup_command_queue()" added to usb-linus

This is a note to let you know that I've just added the patch titled

xhci: Cleanup current_cmd in xhci_cleanup_command_queue()

to my usb git tree which can be found at
git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/usb.git
in the usb-linus branch.

The patch will show up in the next release of the linux-next tree (usually sometime within the next 24 hours during the week.)

The patch will hopefully also be merged in Linus's tree for the next -rc kernel release.

If you have any questions about this process, please let me know.

From: Jeffy Chen <[email protected]>
Date: Fri, 6 Oct 2017 17:45:28 +0300
Subject: xhci: Cleanup current_cmd in xhci_cleanup_command_queue()

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.

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

index a9443651ce0f..48ae15afa59e 100644
@@ -1309,6 +1309,7 @@ static void xhci_complete_del_and_free_cmd(struct xhci_command *cmd, u32 status)
 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);
 }

2.14.2