On 02.12.2016 04:29, Lu Baolu wrote:
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: <sta...@vger.kernel.org> # v3.16+ Signed-off-by: Lu Baolu <baolu...@linux.intel.com> --- 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 bdf6b13..13e05f6 100644 --- a/drivers/usb/host/xhci-ring.c +++ b/drivers/usb/host/xhci-ring.c @@ -1267,14 +1267,16 @@ 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; } + 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) && @@ -1422,6 +1424,10 @@ 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; + } else { + xhci_warn(xhci, "WARN current_cmd doesn't match command\n"); } event_handled:
Thanks, I might do some tweaking to (or remove) the warn message when applying if that is ok -Mathias
