From e224b8b7215fbaf0b7ce70dded685f635412369a Mon Sep 17 00:00:00 2001 From: Lu Baolu Date: Tue, 3 Jan 2017 18:28:46 +0200 Subject: [PATCH] usb: xhci: fix possible wild pointer commit 2b985467371a58ae44d76c7ba12b0951fee6ed98 upstream. 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. Signed-off-by: Lu Baolu Signed-off-by: Mathias Nyman Signed-off-by: Greg Kroah-Hartman --- drivers/usb/host/xhci-ring.c | 16 +++++++++++----- 1 file changed, 11 insertions(+), 5 deletions(-) diff --git a/drivers/usb/host/xhci-ring.c b/drivers/usb/host/xhci-ring.c index 62a5c8d5e028..5f2951dd4d79 100644 --- a/drivers/usb/host/xhci-ring.c +++ b/drivers/usb/host/xhci-ring.c @@ -1268,14 +1268,18 @@ 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->status == COMP_CMD_ABORT) - second_timeout = true; - xhci->current_cmd->status = COMP_CMD_ABORT; + + 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); if ((xhci->cmd_ring_state & CMD_RING_STATE_RUNNING) && @@ -1424,6 +1428,8 @@ 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: -- 2.11.0