usb: xhci: fix possible wild pointer (2b985467) · Commits · 戴 / test

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:

Lu Baolu <baolu.lu@linux.intel.com> Signed-off-by:

Mathias Nyman <mathias.nyman@linux.intel.com> Signed-off-by:

Greg Kroah-Hartman <gregkh@linuxfoundation.org>

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:

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