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Commit 2b985467 authored by Lu Baolu's avatar Lu Baolu Committed by Greg Kroah-Hartman
Browse files

usb: xhci: fix possible wild pointer 



handle_cmd_completion() frees a command structure which might be still
referenced by xhci->current_cmd.
This might cause problem when xhci->current_cmd is accessed after that.

A real-life case could be like this. The host takes a very long time to
respond to a command, and the command timer is fired at the same time
when the command completion event arrives. The command completion
handler frees xhci->current_cmd before the timer function can grab
xhci->lock. Afterward, timer function grabs the lock and go ahead with
checking and setting members of xhci->current_cmd.

Cc: <stable@vger.kernel.org> # v3.16+
Signed-off-by: default avatarLu Baolu <baolu.lu@linux.intel.com>
Signed-off-by: default avatarMathias Nyman <mathias.nyman@linux.intel.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 28bedb5a

drivers/usb/host/xhci-ring.c

+11 −5
Original line number Diff line number Diff line
@@ -1267,13 +1267,17 @@ void xhci_handle_command_timeout(unsigned long data) 
	bool second_timeout = false;

	xhci = (struct xhci_hcd *) data;



	/* mark this command to be cancelled */

	spin_lock_irqsave(&xhci->lock, flags);

	if (xhci->current_cmd) {



	if (!xhci->current_cmd) {

		spin_unlock_irqrestore(&xhci->lock, flags);

		return;

	}



	/* mark this command to be cancelled */

	if (xhci->current_cmd->status == COMP_CMD_ABORT)

		second_timeout = true;

	xhci->current_cmd->status = COMP_CMD_ABORT;

	}



	/* Make sure command ring is running before aborting it */

	hw_ring_state = xhci_read_64(xhci, &xhci->op_regs->cmd_ring);
@@ -1422,6 +1426,8 @@ static void handle_cmd_completion(struct xhci_hcd *xhci, 
		xhci->current_cmd = list_entry(cmd->cmd_list.next,

					       struct xhci_command, cmd_list);

		mod_timer(&xhci->cmd_timer, jiffies + XHCI_CMD_DEFAULT_TIMEOUT);

	} else if (xhci->current_cmd == cmd) {

		xhci->current_cmd = NULL;

	}



event_handled: