From a5a1b9514154437aa1ed35c291191f82fd3e941a Mon Sep 17 00:00:00 2001 From: Mathias Nyman Date: Tue, 3 Jan 2017 18:28:48 +0200 Subject: [PATCH] xhci: Handle command completion and timeout race If we get a command completion event at the same time as the command timeout work starts on another cpu we might end up aborting the wrong command. If the command completion takes the xhci lock before the timeout work, it will handle the command, pick the next command, mark it as current_cmd, and re-queue the timeout work. When the timeout work finally gets the lock It will start aborting the wrong command. This case can be resolved by checking if the timeout work is pending inside the timeout function itself. A new timeout work can only be pending if the command completed and a new command was queued. If there are no more commands pending then command completion will set the current_cmd to NULL, which is already handled in the timeout work. Cc: Reported-by: Baolin Wang Signed-off-by: Mathias Nyman Signed-off-by: Greg Kroah-Hartman --- drivers/usb/host/xhci-ring.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) diff --git a/drivers/usb/host/xhci-ring.c b/drivers/usb/host/xhci-ring.c index bc8be6f6669e..935193c6bf23 100644 --- a/drivers/usb/host/xhci-ring.c +++ b/drivers/usb/host/xhci-ring.c @@ -1269,7 +1269,11 @@ void xhci_handle_command_timeout(unsigned long data) spin_lock_irqsave(&xhci->lock, flags); - if (!xhci->current_cmd) { + /* + * If timeout work is pending, or current_cmd is NULL, it means we + * raced with command completion. Command is handled so just return. + */ + if (!xhci->current_cmd || timer_pending(&xhci->cmd_timer)) { spin_unlock_irqrestore(&xhci->lock, flags); return; }